Pollen from these stamens fertilizes the hefty breast-like female flowers—which have a moist ovule positioned precisely where you'd expect the nipple to be.
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Not only is the male flower a huge brown phallic rod; the female blossoms are simulacra of DD+ breasts, each with its own nectarlactating nipple-like ovule.
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Junior Simon Ovule, a 6-10 center from Nigeria, is averaging 10 points and six rebounds, while 22-220 Russian forward Artem Tavakalyan chips in 213.5 points and 23 rebounds.
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However, an infected ovule is a more important factor for the spread of this disease. The disease is more likely to spread when an infected ovule produces progeny with infected pollen, with a 70% transmission rate. When an infected ovule is pollinated by an uninfected pollen there is only about a 66% transmission rate. In an uninfected ovule that is pollinated by infected pollen there is only about a 3% transmission rate to the offspring.
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Ovule structure (anatropous) 1: nucleus 2: chalaza 3: funiculus 4: raphe Ovule orientation may be anatropous, such that when inverted the micropyle faces the placenta (this is the most common ovule orientation in flowering plants), amphitropous, campylotropous, or orthotropous (anatropous are common and micropyle is in downward position and chalazal end in on the upper position hence, in amphitropous the anatropous arrangement is tilted 90 degrees and in orthotropus it is completely inverted) . The ovule appears to be a megasporangium with integuments surrounding it. Ovules are initially composed of diploid maternal tissue, which includes a megasporocyte (a cell that will undergo meiosis to produce megaspores). Megaspores remain inside the ovule and divide by mitosis to produce the haploid female gametophyte or megagametophyte, which also remains inside the ovule.
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The sperm are transferred from the pollen through the pollen tube to the ovule. Pollen tube growth Unlike animal sperm which is motile, plant sperm is immotile and relies on the pollen tube to carry it to the ovule where the sperm is released. The pollen tube penetrates the stigma and elongates through the extracellular matrix of the style before reaching the ovary. Then near the receptacle, it breaks through the ovule through the micropyle (an opening in the ovule wall) and the pollen tube "bursts" into the embryo sac, releasing sperm.
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Just below it is a small pore, representing the micropyle of the ovule.
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The host yucca plant regulates the number of eggs laid by selectively abscessing flowers that are overburdened with eggs. The plant selects which flowers to abscess by assessing its weight due to the excess of eggs and by recognizing severe ovule damage due to excessive oviposition. In T. intermedia, the moth avoids ovipositing into the ovule directly. Thus, the plant does not perceive ovule damage, and will not abort the flower.
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After fertilization, the ovule develops into a seed containing the embryo. In flowering plants, the female gametophyte (sometimes referred to as the embryo sac) has been reduced to just eight cells inside the ovule. The gametophyte cell closest to the micropyle opening of the ovule develops into the egg cell. Upon pollination, a pollen tube delivers sperm into the gametophyte and one sperm nucleus fuses with the egg nucleus.
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We have already examined in some detail the structure of the macrosporangium or ovule.
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A megasporangium enclosed in a protective layer called an integument is known as an ovule. After fertilisation by means of sperm produced by pollen grains, an embryo sporophyte develops inside the ovule. The integument becomes a seed coat, and the ovule develops into a seed. Seed plants can survive and reproduce in extremely arid conditions, because they are not dependent on free water for the movement of sperm, or the development of free living gametophytes.
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Tieghem placed Aquifoliaceae near Solanaceae because of the unitegmic ovule and the isomerous stamens alternating with the petals.
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Trigonocarpus, the seed/ovule of Medullosales such as Macroneuropteris In 1938, W. A. Bell studied the Sydney Coalfield in Nova Scotia, and suggested that the large fossilized seeds called Trigonocarpus noeggerati could be the ovules of Macroneuropteris scheuchzeri. Erwin Zodrow in 2002 also noted that this ovule fossil was commonly in physical association with M. scheuchzeri foliage. Specimens of Trigonocarpus can be quite large. The largest recorded was 10 cm and has been noted as the largest ovule produced by a non-angiosperm seed-plant.
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Dipentodon and Perrottetia are distinctive in that the calyx and corolla are not well differentiated, but resemble each other. Tapiscia and Huertea have a calyx tube and compound, rather than simple leaves. Tapiscia has a uniloculate ovary with a single ovule. Huertea has one locule containing two ovules, or two locules, each containing one ovule.
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The resulting zygote develops into an embryo inside the ovule. The ovule, in turn, develops into a seed and in many cases, the plant ovary develops into a fruit to facilitate the dispersal of the seeds. Upon germination, the embryo grows into a seedling. Gene expression pattern determined by histochemical GUS assays in Physcomitrella patens.
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Heat stress can also have a detrimental effect on plant reproduction. Temperatures 10 degrees Celsius or more above normal growing temperatures can have a bad effect on several plant reproductive functions. Pollen meiosis, pollen germination, ovule development, ovule viability, development of the embryo, and seedling growth are all aspects of plant reproduction that are affected by heat.
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They have narrow, linear spreading juvenile leaves that gradually change into more strongly keeled and appressed scales. Female cones are borne singly and at the ends of branches and each has 3–5 bracts with very elongated bases. Each fertile bracts supports an erect ovule in its axil and this ovule remains erect throughout its development.
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The ovules are approximately 50 in each carpel, one of the structural units of a pistil, representing a modified, ovule-bearing leaf.
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11 p. [Coates et al. 1994] Common causes of empty seed are lack of pollination, abortion of the ovule, and insect damage.
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This is probably because rice has a monocarpellary ovary with a single ovule and transcripts associated with such events may be masked.
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The ovary is the female organ, contains ovule which develops into seeds. Ovary is elliptical, with a massive style and green stigma lobes.
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The seed plants, which include conifers and flowering plants have small gametophytes that develop inside the pollen grains (male) and the ovule (female).
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This process is called pollination. In gymnosperms (literally naked seed) pollen comes into direct contact with the exposed ovule. In angiosperms the ovule is enclosed in the carpel, requiring a specialised structure, the stigma, to receive the pollen. On the surface of the stigma, the pollen germinates; that is, the male gametophyte penetrates the pollen wall into the stigma, and a pollen tube, an extension of the pollen grain, extends towards the carpel, carrying with it the sperm cells (male gametes) until they encounter the ovule, where they gain access through a pore in the ovule's integument (micropyle), allowing fertilisation to occur.
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One to three (rarely six) carpels are fused to a superior ovary with one (rarely two) basal ovule. Idioblasts are found in the tissues.
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The tip of the pollen tube then enters the ovary and penetrates through the micropyle opening in the ovule. The pollen tube proceeds to release the two sperm in the megagametophyte. The cells of an unfertilized ovule are 8 in number and arranged in the form of 3+2+3 (from top to bottom) i.e. 3 antipodal cells, 2 polar central cells, 2 synergids & 1 egg cell.
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Flowering plants generate gametes using a specialized cell division called meiosis. Meiosis takes place in the ovule (a structure within the ovary that is located within the pistil at the center of the flower) (see diagram labeled "Angiosperm lifecycle"). A diploid cell (megaspore mother cell) in the ovule undergoes meiosis (involving two successive cell divisions) to produce four cells (megaspores) with haploid nuclei.Snustad DP, Simmons MJ (2008).
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In most flowering plants, the pollen tube enters the ovule through the micropyle opening in the integuments for fertilization (porogamy). In chalazogamous fertilization, the pollen tubes penetrate the ovule through the chalaza rather than the micropyle opening. Chalazogamy was first discovered in monoecious plant species of the family Casuarinaceae by Melchior Treub, but has since then also been observed in others, for example in pistachio and walnut.
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Three antipodal cells form on the opposite (chalazal) end of the ovule and later degenerate. The large central cell of the embryo sac contains two polar nuclei.
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Some have noted that the large size of these seeds may have allowed them to float, like small coconuts, to be distributed in these coastal mangrove-like areas as well as inland wetland forests. Their three-part symmetry gives them their name. A tube-like opening at the top brought pollen into the ovule. Pachytesta is a term that is also used for this type of seed/ovule.
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The paper was essentially divided into three parts. A treatment of Kingia comes first; the genus is formally described and explicitly named after the Kings, and tentatively placed in Liliaceae. Then follows a detailed description of the ovule of Kingia, which acts as a bridge to the following parts. In the second part, Brown sets down for the first time the modern view of the anatomy and development of the angiosperm ovule.
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Ovary sunken in the tissue of the receptacle; style lateral. Perianth vaguely 2 lobed; mouth almost closed. Ovule pendulous, style lateral. The fruit is a crustaceous achene, sunken, 2 mm.
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The ovule contains a megagametophyte, also known as an embryo sac, that is bipolar in structure and contains 8 cell nuclei. The antipodal cells are persistent, and the endosperm is triploid.
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The pollen is furrowed. The female strobili also occur in whorls, with bracts which fuse around a single ovule. There are generally 1-2 yellow to dark brown seeds per strobilus.
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Cast of Trigonocarpus trilocularis ovule showing stalk attachment; Massillon Sandstone (Upper Carboniferous), NE Ohio. Cast of a Trigonocarpus ovule showing one of the three longitudinal ribs. Ovules in different medullosalean species could vary from maybe 1 cm to over 10 cm long - the latter being the largest known ovules produced by any non-angiosperm seed-plant. It was traditionally believed that the ovules were borne directly on the fronds, replacing one of the pinnules on the ultimate pinnae.
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Depending on the organ cultured, it may be referred to as either embryo, ovule, or ovary culture. Ovule culture or in ovolo embryo culture is a modified technique of embryo rescue whereby embryos are cultured while still inside their ovules to prevent damaging them during the excision process. Ovary or pod culture, on the other hand employs the use of an entire ovary into culture. It becomes necessary to excise the entire small embryo to prevent early embryo abortion.
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In flowering plants, the female gametophyte has been reduced to an eight-celled embryo sac within the ovule inside the ovary of the flower. Oogenesis occurs within the embryo sac and leads to the formation of a single egg cell per ovule. In ascaris, the oocyte does not even begin meiosis until the sperm touches it, in contrast to mammals, where meiosis is completed in the estrus cycle. In female Drosophila flies, genetic recombination occurs during meiosis.
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Ovule and seed development of Lacandonia schismatica (Lacandoniaceae). American Journal of Botany, 85(3): 299-304.Márquez-Guzmán, J., Vázquez-Santana, S., Engleman, E. M., Martínez-Mena, A., and Martínez, E. (1993).
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There are a few ways that reproduction occurs within plant life, and one way is through parthenogenesis. Parthenogenesis is defined as "a form of asexual reproduction in which genetically identical offspring (clones) are produced". Another form of reproduction is through cross-fertilization, which is defined as "fertilization in which the egg and sperm are produced by different individuals", and in plants this occurs in the ovule. Once an ovule is fertilized within the plant this becomes what is known as a seed.
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Although most yucca moths deposit their eggs in the ovule of the flower, Tegeticula employs different methods of laying eggs. T. intermedia employs superficial oviposition, meaning that the yucca moth lays its eggs very slightly beneath the plant tissue, so as not to damage the yucca ovule. This strategy allows the moth to bypass the yucca plant's regulation of the number of eggs it hosts, leading to exploitation of the plant. Oviposition takes place in the fruit of the yucca.
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Although many factors may contribute to determining ovule number, one way for females to increase the level of pollen competition is to decrease ovule number while maintaining stigma size. The evolution of functional syncarpy (assuming no other attendant changes) presumably is a simultaneous increase in the number of ovules accessible from one stigma, which tended to decrease the intensity of pollen competition, and a concentration of pollen deposition on a single stigma, which tends to increase pollen competition. Further increases in pollen competition could be brought about by an increase in pollen delivery (through change of pollinator, increased attractiveness of floral display, or rewards), a decrease in ovule number or stigma size, changes in temporal patterns of stigma receptivity, or changes in the competitive environment of the carpel .
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Tokuoka, T. (2007). Molecular Phylogenetic Analysis of Euphorbiaceae Sensu Stricto Based on Plastid and Nuclear DNA Sequences and Ovule and Seed Character Evolution. Journal of Plant Research 120: 511–22. ;Species # Cocconerion balansae Baill.
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The ovary is slender, softly hairy and contains one pendulous ovule, it is difficult to determine where it merges into the style. It is subtended by four blunt or line- to thread-shaped scales.
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The connective tissue between the lobes of the anthers extends above their tops. Its flowers have 10 pistils with smooth carpels, no apparent styles and elongate stigma (botany). Each ovule has 8-10 ovaries.
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Ocotea catharinensis is a slow- growing monoecious evergreen hardwood up to 40m tall. Its flowers are small and hermaphrodite. The ovary is glabrous with a well developed ovule. Often not all the locelli are fertile.
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The number of carpels is described by terms such as tricarpellate (three carpels). Carpels are thought to be phylogenetically derived from ovule-bearing leaves or leaf homologues (megasporophylls), which evolved to form a closed structure containing the ovules. This structure is typically rolled and fused along the margin. Although many flowers satisfy the above definition of a carpel, there are also flowers that do not have carpels according to this definition because in these flowers the ovule(s), although enclosed, are borne directly on the shoot apex.
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Plant ovules with megasporocytes before meiosis: Gymnosperm ovule on left, angiosperm ovule (inside ovary) on right After megasporogenesis, the megaspore develops into the female gametophyte (the embryo sac) in a process called megagametogenesis. The process of megagametogenesis varies depending on which pattern of megasporogenesis occurred. Some species, such as Tridax trilobata, Ehretia laevis, and Alectra thomsoni, can undergo different patterns of megasporogenesis and therefore different patterns of megagametogenesis. If the monosporic pattern occurred, the single nucleus undergoes mitosis three times, producing an eight-nucleate cell.
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Leaves all basal, floating or aerial, ovate to elliptical, cordate or subcordate. Flowers hermaphrodite, in racemes or panicles. Stamens 6(-11). Carpels few or numerous in a single whorl, free, each with 1 ovule; styles subventral.
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As the zygote develops into an embryo, the triploid cell develops into the endosperm, which serves as the embryo's food supply. The ovary will now develop into a fruit and the ovule will develop into a seed.
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Its flowers have 126-180 stamen. Its flowers have 15-32 carpels. Each carpel has 1 ovule, a straight style, and a 2-3 lobed stigma. Its fruit are on pedicels that are 0.8-2.0 centimeters long.
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The proposed advantages of LSI compared to normal SI mechanisms is that LSI would allow the maternal parent to evaluate the paternal genetic material and allow ovule development depending on the vigor of developing embryos or amount of resources available. On the other hand, plants with LSI may face a disadvantage from seed discounting, which results in a reduction in fecundity. When pollen tubes reach the ovule, they are no longer available to be fertilized by outcrossed pollen, meaning LSI still uses up ovules for potential outcrossing while other SI methods do not.
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The inside of a Ginkgo seed, showing the embryo Flowering plants (angiosperms) create embryos after the fertilization of a haploid ovule by pollen. The DNA from the ovule and pollen combine to form a diploid, single- cell zygote that will develop into an embryo. The zygote, which will divide multiple times as it progresses throughout embryonic development, is one part of a seed. Other seed components include the endosperm, which is tissue rich in nutrients that will help support the growing plant embryo, and the seed coat, which is a protective outer covering.
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Seeds are the product of the ripened ovule, after fertilization by pollen and some growth within the mother plant. The embryo is developed from the zygote and the seed coat from the integuments of the ovule. Seeds have been an important development in the reproduction and success of gymnosperm and angiosperm plants, relative to more primitive plants such as ferns, mosses and liverworts, which do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological niches on land, from forests to grasslands both in hot and cold climates.
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The pistil consists of two connate carpels. The style has two lobes. Stigmatic tissue may be located in the interior surface or form two lateral lines. The ovary is inferior and has only one ovule, with basal placentation.
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Pinguicula lutea is a perennial herbaceous plant. The leaves of P. lutea are yellowish-green basal rosettes. The simple shape leaf blade displaces from ovule to oblong.eNature, Yellow Butterwort, 2007 P. lutea has curved leaves and pointed tip.
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There are three conspicuous fleshy stigmas, reflexed, with a basally attached ovule. The beaked fruit is ovoid to pear shaped, covered in reflexed scales, with a thin mesocarp. Each fruit carries one basally attached seed with a basal embryo.
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Anthers typically consist of four microsporangia and an ovule is an integumented megasporangium. Both types of spores develop into gametophytes inside sporangia. As with all heterosporous plants, the gametophytes also develop inside the spores, i. e., they are endosporic.
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The leaf veins of Huberantha form an interconnected net-like pattern. Their flowers are axillary. They have a single ovule and seed per ovary. A portion of their ovules remain fused to the seed coat forming a flat raphe.
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The stamens are inserted at the top of the tube. The ovary is sessile, with one ovule. The fruit is a narrow nut, topped with a rounded- triangular concave plate (5-6 mm wide) and hairy on the outside.
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The integument – the covering on the outside of the ovule – is in the form of a long coiled tube, an unusual feature in flowering plants. The fruit which forms after fertilization is a fleshy drupe, to which the stigma remains attached.
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Pollen-producing cones fusiform (tapering at both ends), microsporophylls (male, pollen-producing) up to 45 mm long. Megasporophylls (female, ovule-producing) up to 30 cm long, each with 2-5 ovules. Seeds flattened to ovoid, orange-brown.Lindstrom, AJ, & KD Hill. 2002.
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Leaves aerial, elliptical to lanceolate or linear-lanceolate. Flowers hermaphrodite, in 1 - 3 whorls in umbels or racemes, or long- pedunculate in leaf-axils. Stamens 6. Carpels numerous, spirally arranged in a globose head, free, each with 1 ovule; styles apical.
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Carpels 6–15 in an irregular whorl, free, each with 1 ovule; styles apical. Fruitlets achenial, longitudinally many-ribbed, with a short apical beak. 2n = 42. Floating water plantain Luronium natans showing stoloniferous habit Characteristic 'ladder' venation pattern of submerged leaves.
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ROS levels have been shown via GFP to be at their highest during floral stages when the ovule is the most receptive to pollen tubes, and lowest during times of development and following fertilization. High amounts of ROS activate Calcium ion channels in the pollen tube, causing these channels to take up Calcium ions in large amounts. This increased uptake of calcium causes the pollen tube to rupture, and release its sperm into the ovule. Pistil feeding assays in which plants were fed diphenyl iodonium chloride (DPI) suppressed ROS concentrations in Arabidopsis, which in turn prevented pollen tube rupture.
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One type of automatic self-pollination occurs in the orchid Ophrys apifera. One of the two pollinia bends itself towards the stigma. Self-pollination is when pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms). There are two types of self-pollination: in autogamy, pollen is transferred to the stigma of the same flower; in geitonogamy, pollen is transferred from the anther of one flower to the stigma of another flower on the same flowering plant, or from microsporangium to ovule within a single (monoecious) gymnosperm.
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Chloroplast capture is an evolutionary process through which inter-species hybridization and subsequent backcrosses yield a plant with new genetic combination of nuclear and chloroplast genomes.Rieseberg. L. H. and Soltis, D. E. (1991) Phylogenetic consequences of cytoplasmic gene flow in plants . Evolutionary Trends in Plants 5: 65-84 For instance, 1) species A's (having chloroplast genome a and nuclear genome AA) pollen hybridizes (backcross) to species B's (b and BB) ovule, yielding the 1st hybrid (F1) with chloroplast genome b and nuclear genome A (50%) and B (50%); 2) species A's pollen again hybridizes (backcross) to F1's ovule, yielding the 2nd hybrid (F2) with chloroplast genome b and nuclear genome A (75%) and B (25%); 3) species A's pollen again hybridizes (backcross) to F2's ovule, yielding the 3rd hybrid (F3) with chloroplast genome b and nuclear genome A (87.5%) and B (12.5%); 4) after further backcross generations, a plant is obtained with the new genetic combination (chloroplast genome b and nuclear genome A).
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In the pistillate flowers, ovaries are single or sometimes quadri- or quinticelled. One to three styles and one ovule occur in each cavity. Fruits rarely open at maturity and are most often drupes. Seed coats are very thin or are crust- like.
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Stamens are reflexed in anthesis and have basal and apical sterile appendages. Many species also exhibit secondary pollen presentation. The 5-locular ovary contains two ovules per locule. The drupaceous fruits contain pyrenes with one seed due to the abortion of one ovule.
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In the peach plant, the style environment in which the pollen tube grows through, provides nutrition for the tube's growth to the ovule. Pollen tubes are tolerant and even pollen damaged by X-rays and gamma rays can still grow pollen tubes.
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Female gametangia are most commonly called archegonia. They produce egg cells and are the sites for fertilization. Archegonia are common in algae and primitive plants as well as gymnosperms. In flowering plants, they are replaced by the embryo sac inside the ovule.
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The carpel is not stylate, apically stigmatic with the stigma peltate, or umbonate. These flowers only present one ovule pendulous, nonarillate, campylotropous, bitegmic, and crassinucellate. The placentation is apical and embryo-sac development is of the polygonum type. Before fertilization, they fuse polar nuclei.
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The genus has sometimes been considered to include South American species of Hesperomeles which, like Osteomeles, have only one ovule per locule and hard pyrenes. But Hesperomeles notably have simple leaves, and recent molecular phylogenetics suggest that the two genera are only distantly related.
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Pollen particles are solitary, terminal, ca. 3–5 mm long. Appendage is adnate to base of carpel, cortex, inverted, with a drooping ovule. The fruit of mountain pine consists of a dark brown, black-brown to purple-brown seed in a fleshy, waxy white cup.
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The female flowers have four perianth lobes, and are clavate-tubular and decussate-imbricate. The ovary in this genus is enclosed, with a short style, a capitate or ligulate (in P. subgen. Ligulistigma) stigma; the ovule is orthotropous. The seeds have little or no endosperm.
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The species Scindapsus pictus is common in cultivation. Scindapsus is not easily distinguishable from Epipremnum. The main difference between the two genera is in the number of seeds they produce. Scindapsus species have one ovule in each ovary whereas Epipremnum species have a few.
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Therefore, pollen must submerge through the pollination droplet which brings the male gametophyte to the egg of the exposed ovule. However, pollen of different species will not submerge into the droplet; the pollen is left floating atop, while the droplet retracts back into the micropyle.
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In almost all embryophytes, including most gymnosperms and all angiosperms, the male gametophytes (pollen grains) are the primary mode of dispersal, for example via wind or insect pollination, eliminating the need for water to bridge the gap between male and female. Each pollen grain contains a spermatogenous (generative) cell. Once the pollen lands on the stigma of a receptive flower, it germinates and starts growing a pollen tube through the carpel. Before the tube reaches the ovule, the nucleus of the generative cell in the pollen grain divides and gives rise to two sperm nuclei, which are then discharged through the tube into the ovule for fertilization.
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Cross section of ovule in gymnosperms and angiospermsGymnosperm pollen is produced in microsporangia borne on the scales of the male cone or microstrobilus. In most species the plants are wind-pollinated, and the pollen grains of conifers have air bladders that provide buoyancy in air currents. The grains are deposited in the micropyle of the ovule of a female cone or megastrobilus, where they mature for up to a year. In conifers and Gnetophytes the pollen germinate to produce a pollen tube that penetrates the megasporangium or nucellus carrying with it sperm nuclei that are transferred to the egg cell in the developing archegonia of the female plant.
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The species is dioecious. The male pollen cones are 5-7 millimeters long with spirally arranged triangular sporophylls. The female seed cones each have a single subterminal fertile cone scale with a single ovule developing into a seed. The seed is covered by a fleshy epimatium.
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The stamens of the third whorl has 2 glands near its base. These are 2–4 locular, with locules opening by valves. There is one pistil and one carpel. There is a one locular ovary with a basal placentation; one ovule; a subsessile stigma, which is discoid or capitate.
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The Smilax glauca is a monocot from the family Smilacaceae. The Smilacaceae family comprises herbaceous vines and woody lianas typically with prickles and tendrils. Flowers have six tepals and stamens and the ovule bearing flowers have one superior ovary. Smilax glauca has the common name of cat greenbrier.
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Pollen tubes act as conduits to transport the male gamete cells from the pollen grain—either from the stigma (in flowering plants) to the ovules at the base of the pistil or directly through ovule tissue in some gymnosperms. Pollen grains have separate structures such as microsporocytes and megasporocytes.
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For pollination to occur, pollen grains must attach to the stigma of the female reproductive structure (carpel), where the female gametophytes (ovules) are located inside the ovary. After the pollen tube grows through the carpel's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization. The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte(s), then grows into a fruit, which surrounds the seed(s).
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For the pollen grain, the male gametophyte, to transmit its genetic material to the ovule, it must germinate and form a pollen tube that extends down nearly the full length of the corn silk strand. Typically 400 to 600 kernels are successfully formed in this way. The pollen tube extends at a rate of over 1 centimeter per hour, requiring only 24 hours to create a foot-long pathway within the intercellular space of the corn silk, through which the sperm cells (the gametes) pass to join the female gametophyte within the ovule. The pollen tube is produced by the single vegetative cell in the pollen grain, which passes its cytoplasm, nucleus and two sperm cells into the tube.
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The alternative interpretation, preferred by von Balthazar et al., is that there are two flowers very close together, each with a single carpel. Only the smaller "scale" might then correspond to a tepal. Each carpel has a broad two-crested stigma on a short style, and usually contains a single ovule.
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The ovary consists of three united carpels that form a single locule, which produces only one ovule. The ovary is superior with basal or free-central placentation. The gynoecium terminates in 1 to 3 styles, each of which ends in a single stigma.Samuel B. Jones and Arlene E. Luchsinger. 1979.
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Infective second stage juveniles colonize plants during the vegetative growth stage and may feed ectoparasitically during this time. When the inflorescence begins to form, the J2s invade the flower ovule and begin to feed endoparasitically.Stynes, B.A., and Bird, A.F. 1982. Development of galls induced in Lolium rigidum by Anguina agrostis.
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"Some Lower Carboniferous pteridosperm cupules bearing ovules and microsporangia." Transactions of the Royal Society of Edinburgh, 70: 1-11. but by Pennsylvanian times there was normally just a single ovule per cupule. A number of cases have been found of cupules occurring in clusters at the ends of branching axes.
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The seed coat develops from the maternal tissue, the integuments, originally surrounding the ovule. The seed coat in the mature seed can be a paper-thin layer (e.g. peanut) or something more substantial (e.g. thick and hard in honey locust and coconut), or fleshy as in the sarcotesta of pomegranate.
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It flowers between January and October. Diplospory, a type of Agamospermy, occurs during the development of female gametophyte in the ovule and hence reduction division does not take place in the Megaspore mother cell. The diploid egg is unfertilized and forms the embryo. Hence daughter plants are exactly clones of the mother.
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When a pollen grain adheres to the stigma of a carpel it germinates, developing a pollen tube that grows through the tissues of the style, entering the ovule through the micropyle. When the tube reaches the egg sac, two sperm cells pass through it into the female gametophyte and fertilisation takes place.
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The mature seeds of A. mirabilis are about long and wide. The seed integument has three layers of tissues - the sarcotesta, the thickened sclerotesta, and endotesta. It is fused to the nucellus (central portion of the ovule) only at the base. The sclerotesta (the "shell") also exhibits a zigzag pattern of sclereids.
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This was a profoundly important discovery: in 1890, Julius von Sachs declared that "no more important discovery was ever made in the domain of comparative morphology and systematic Botany". That Brown was able to observe the gymnosperm ovule at all is remarkable given the difficulty of finding the same with a modern microscope.
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Sepals may be any color. The pistils have one ovule. The flowers have nectaries, but petals are missing in the majority of species. The fruits are ovoid to obovoid shaped achenes that are collected together in a tight cluster, ending variously lengthened stalks; though many species have sessile clusters terminating the stems.
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Plants with reduced exposure to pollinators were 33% to 50% less likely to produce fruits than those that were, while hand pollinated individuals showed a 100% fruit set (though these fruits did not contain a 100% seed set). Plant resources were shown to be a limiting factor in seed production: when pollen was in abundance, larger plants had a significantly greater seed to ovule ratio than smaller ones. The overall suboptimal seed to ovule ratios suggest that Trillium grandiflorum has evolved to maximize reproductive success in the face of highly stochastic pollination, where some plants may only be visited by a single pollinator in a season. Trillium grandiflorum has been studied extensively by ecologists due to a number of unique features it possesses.
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The fertile scale has one seed producing ovule. The single seed of the cone is covered by a modified ovuliferous scale known as the epimatium. The epimatium becomes fleshy and drupe-like at maturity. It varies in shape from elliptic to ovoid or pyriform and may be red, violet or purplish brown in color.
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A collection of flowers forming an inflorescence. The characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, and provide the most trustworthy external characteristics for establishing relationships among angiosperm species. The function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds.
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The fruit can be a capsule, berry, or nut, all containing only two seeds per one locule (one ovule/ovary). Convolvulus sepium, slightly reduced. The leaves and starchy, tuberous roots of some species are used as foodstuffs (e.g. sweet potato and water spinach), and the seeds are exploited for their medicinal value as purgatives.
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Plants which reproduce sexually also have gametes. However, since plants have an alternation of diploid and haploid generations some differences exist. In flowering plants, the flowers use meiosis to produce a haploid generation which produce gametes through mitosis. The female haploid is called the ovule and is produced by the ovary of the flower.
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The flowers are usually clustered in the leaf axil, although they are solitary in some species. The calyx of the flowers has four lobes, and the corolla consists of four petals. The ovary consists of two locules; each locule has a single ovule which develops into a single seed. The fruit is a drupe.
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Caytonia was first described by Hamshaw Thomas in 1925. His close examination of the cupules led him to believe this was one of the earliest examples of angiosperms. He mistakenly thought the entire ovule was enclosed in the cupule, unlike typical gymnosperms. He worked meticulously, collecting and cleaning specimens to get the best understanding.
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Proembryo, or pro-embryo, in a flowering plant denotes the series of cells that are formed after fertilization within the ovule of a plant, before formation of the embryo.Webster's Revised Unabridged Dictionary, (1913). In human embryonic development the term is usually changed to pre-embryo to describe the conceptus before implantation in the uterus.
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The anthers are subsessile and linear, sometimes with an apical appendage. The ovary has a single loculus with a single glabrous ovule. The style is lateral, with a simple stigma, which is usually penicillate with short hairs. The fruit is small, typically 1–3 mm, dry, included in the persistent base of the calyx-tube.
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Upon maturation, the neck opens to allow sperm cells to swim into the archegonium and fertilize the egg. The resulting zygote then gives rise to an embryo, which will grow into a new diploid individual (sporophyte). In seed plants, a structure called ovule, which contains the female gametophyte. The gametophyte produces an egg cell.
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The pistillate flowers are larger with broadly imbricate sepals and valvate petals; there are three toothlike staminodes borne at the side of the ovoid, uniovulate gynoecium. The three stigmas are prominent and reflexed nearing antithesis; the ovule is pendulous. The ovoid fruit is red to brown at maturity carrying one seed with a basal embryo.
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Pollen tubes, sperm, and ovule of Cycadophyta Siphonogamy is a condition in plants in which pollen tubes are developed for the transfer of the male cells to the eggs. The seed plants are siphonogamous, while in the lower plants the male cells usually swim to the eggs. As a consequence, the spermatophytes were sometimes called siphonogams.
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There are many theories that propose how flowers evolved. Some of them are described below. The Anthophyte Theory was based on the observation that a gymnospermic family Gnetaceae has a flower- like ovule. It has partially developed vessels as found in the angiosperms, and the megasporangium is covered by three envelopes, like the ovary structure of angiosperm flowers.
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When mature, the haploid ovule produces the female gamete which are ready for fertilization. The male haploid is pollen and is produced by the anther, when pollen lands on a mature stigma of a flower it grows a pollen tube down into the flower. The haploid pollen then produces sperm by mitosis and releases them for fertilization.
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Filaments carry nectaries. The anthers stand upright, with pollen freed from a slit at the top. The style is thread-like without hairs, sticking out above the corolla tube, while the stigma at its tip is club-shaped or split in two. The ovary consists of two carpels with only one ovule, which is pendulous and anatropous.
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He also demonstrated reservations in spontaneous generation by supporting the beliefs of Christian Ehrenberg. Ehrenberg believed that infusoria had complex organ systems while other protozoologists, like Fèlix Dujardin, believed that infusoria were simple organisms that could appear spontaneously. Pouchet did not seem very interested in spontaneous generation during this time, and instead studied ovule production and menstruation.
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There are three to six small, triangular staminodes and the gynoecium is ovoid and covered in brown scales. The three stigmas are apical and reflexed; the ovule is pendulous. The red epicarp of the small round fruit breaks away in age exposing the brown, warty mesocarp. The single seed is spherical with homogeneous endosperm and a subbasal embryo.
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II) Flowers without epicalyx. III) Ovule 1 in each locule; seed 1 in each mericarp. Species- S.acuta I) Leaf base obtuse, apex acute. Vernacular name[6]\- Sanskrit- Bala; Bengali- Kureta/ Berela[7](in Tripura) ; Hindi- Kareta/ Kharenti ; Oriya- Siobala ; Gujrati- Bala/ Jangli menthi ; Marathi- Chikana ; Malayalam- Malatanni ; Tamil- Malaidangi ; Telegu- Nelabenda ; Kannada- Vishakaddi ; Sinhala- Gasbevila ; Burmese- Katsayna ; Yoruba-Ìsékètu.
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The woody, straight-sided, flat pods are oblanceolate, narrowing toward the base and 2-5 cm by 4-9 mm, and have oblique striations. Both the margins and the seed-partitions are prominent. The brown to dark brown seeds are 2.5-3.5 mm long. The stalk of the ovule expands to give a top-shaped aril.
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Over 3,000 greenish-white flowers occur in male panicles, each with five to seven anthers and a nonfunctional ovary. Male flowers have yellow nectaries and five to seven stamens. About 500 greenish-yellow flowers occur in each hermaphroditic panicle. Each flower has six anthers, usually a bilobed stigma, and one ovule in each of its two sections (locules).
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Each flower has about 20–30 stamens with filaments that are smooth. Further, it has ovate nectaries, a hairy receptacle that is 3 to 5 mm long, about 60 to 80 apocarpous (free) carpels. There is only one ovule and stigma per ovary, the styles are straight, and the fruit stalk, 4 to 7 mm long, is dry.
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In animals, egg cells are also known as ova (singular ovum, from the Latin word meaning 'egg'). The term ovule in animals is used for the young ovum of an animal. In vertebrates, ova are produced by female gonads (sex glands) called ovaries. A number of ova are present at birth in mammals and mature via oogenesis.
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In some, however, three other, aborted megaspores were still present that together with the functional megaspore represented the remains of what would have been the tetrad of megaspores in the ancestral pre-seed plants.Schabilion, J. T. & Brotzman, N. C. (1979). "A tetrahedral megaspore arrangement in a seed fern ovule of Pennsylvania age." American Journal of Botany, 66: 744-745.
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The development of the embryo and gametophytes is called embryology. The study of pollens which persist in soil for many years is called palynology. Reproduction occurs when male and female gametophytes interact. This generally requires an external agent such as wind or insects to carry the pollen from the stamen to the vicinity of the ovule.
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The maturing ovule undergoes marked changes in the integuments, generally a reduction and disorganization but occasionally a thickening. The seed coat forms from the two integuments or outer layers of cells of the ovule, which derive from tissue from the mother plant, the inner integument forms the tegmen and the outer forms the testa. (The seed coats of some monocotyledon plants, such as the grasses, are not distinct structures, but are fused with the fruit wall to form a pericarp.) The testae of both monocots and dicots are often marked with patterns and textured markings, or have wings or tufts of hair. When the seed coat forms from only one layer, it is also called the testa, though not all such testae are homologous from one species to the next.
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Pollen is contained in sacs of two to four at the tips of sporophylls on the strobiloid. Ovules of Ginkgo trees come from stalks from leaf axils on the short shoots, each containing two ovules. The ovule is fertilized by the flagellated male gametes, which can move about freely. This fertilization process begins on the tree itself in the spring.
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Meiosis occurs and a megaspore is produced as the first cell of the megagametophyte. As cell division takes place the nucleus of the megaspore thickens, and cell differentiation occurs to produce prothallial tissue containing an ovum. The remaining undifferentiated cells then form the endosperm. When the male structure releases its pollen grains, some fall onto the female strobilus and reach the ovule.
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This contrasts sharply with the pattern exhibited by nearly all animals and by vascular plants. In the more familiar seed plants, the haploid generation is represented only by the tiny pollen and the ovule, while the diploid generation is the familiar tree or other plant.Fosket, Donald E. Plant Growth and Development: A Molecular Approach, p. 27. (San Diego: Academic Press, 1994). .
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At the mouth the sepals spread into lobes that are shorter than the tube. There are no petals, but the lobes of the sepals are quite colourfully petal-like in many species. The ovary is ovoid with a single loculus containing a solitary ovule. The style is lateral, bearing a mop-like stigma that fills the mouth of the calyx-tube.
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The small flowers are only six millimeters across. The ovary is superior and usually has a single ovule; although in pistillate flowers, the stamens are small and infertile. The mature fruit of Rhus integrifolia is sticky, reddish, covered with hairs, and about seven to ten millimeters in diameter. The elliptical fruit presents tight clusters at the very ends of twigs.
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The fertile cone scale has a single inverted ovule developing into a seed. The seed is entirely enclosed by a modified ovuliferous scale known as the epimatium. The epimatium is green or glaucous at first and becomes fleshy and red in color at maturity. The mature epimatium is generally 14-20 millimeters long, 10-13 millimeters wide and pyriform in shape.
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Long, A. G. (1963). "Some specimens of Lyginorachis papilio Kidston associated with stems of Pitys." Transactions of the Royal Society of Edinburgh, 65: 211-224. Many palaeobotanists now interpret these clusters of cupulate organs as fertile fronds, in which the cupulate tissue was derived from the laminate part of the frond that surrounded the ovule and thereby provided added protection for it.
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This could be because the male sporophyte and gametophyte are less protected from the environment than the ovule and embryo sac. Male-sterile plants can set seed and propagate. Female-sterile plants cannot develop seeds and will not propagate. Manifestation of male sterility in CMS may be controlled either entirely by cytoplasmic factors or by interactions between cytoplasmic factors and nuclear factors.
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As the pollen tube continues to grow towards the ovules, the male sperm remains in the apical region and is transported to the female ovule. The pollen tube elongates at a rate comparable to neurite development An example of positive and negative chemotropism is shown by a plant's roots; the roots grow towards useful minerals displaying positive chemotropism, and grow away from harmful acids displaying negative chemotropism.
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Of the four, two are related with the early stage of the disease: ccRNA 1 fast and ccRNA 2 fast. After several years, two other species appear and predominate: ccRNA 1 slow and ccRNA 2 slow. Moreover, they share sequence homology with other viroids. Conditions for a viroid to infect its host include wounds on the host or infected pollen grain deposited into an ovule.
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Angiosperm Phylogeny Website. Version 7, May 2006. Leea is often placed in its own family, Leeaceae, based on morphological differences between it and Vitaceae. These differences include ovule number per locule (two in Vitaceae and one in Leeaceae), carpel number (two in Vitaceae and three in Leeaceae), and the absence or presence of a staminoidal tube (present in Leeaceae) and floral disc (present in Vitaceae).
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In Bryophyte land plants, fertilisation takes place within the archegonium. In flowering plants a second fertilisation event involves another sperm cell and the central cell which is a second female gamete. In flowering plants there are two sperm from each pollen grain. In seed plants, after pollination, a pollen grain germinates, and a pollen tube grows and penetrates the ovule through a tiny pore called a micropyle.
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In 2015, Eslamian et al. found a correlation between the composition of the sperm lipid membrane and the odds of having asthenozoospermia. The sperm that have more polyunsaturated fatty acids, such as docosahexaenoic acid (DHA) shown better fertility results. DHA (docosahexaenoic acid) is an acid form by six double bons which allows the fluidity of the membrane, necessary to the fusion with the ovule.
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Hylocereus undatus, a hermaphrodite plant with both carpels and stamens. Hermaphrodite is used in botany to describe a flower that has both staminate (male, pollen-producing) and carpellate (female, ovule-producing) parts. This condition is seen in many common garden plants. A closer analogy to hermaphroditism in botany is the presence of separate male and female flowers on the same individual—such plants are called monoecious.
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PNRSV can be transmitted through plant propagation methods, making spread through tree nursery stock and root grafting in orchards problematic. The virus also has been shown to infect and transmit through pollen and seeds. PNRSV has been shown to be transmitted by bees carrying infected pollen into orchards. PNRSV infects all seed parts, therefore infection of seed can occur from an infected pollen grain, ovule, or both.
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Three incomplete locules are present, each bearing one antropous, basally attached ovule. The fruit has one, rarely two seeds, covered in persistent perianth whorls, and stigmatic apical remains. The epicarp is matted in irregular vertical rows of reflexed scales, with a thin mesocarp and an undifferentiated endocarp. The seed is basally attached, spherical, usually depressed, with a thick sarcoesta, a homogeneous endosperm and a basal embryo.
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A disk of woody tissue (a hypostase) is present at the base of the ovule. The subfamily Xanthorrhoeoideae contains only the genus Xanthorrhoea, native to Australia. Plants typically develop thick woody stems; the flowers are arranged in a dense spike. Members of the subfamily Asphodeloideae are often leaf succulents, such as aloes and haworthias, although the subfamily also includes ornamental perennials such as red hot pokers (Kniphofia).
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Its flowers are known to have a strong scent similar to that of human semen. The flower have bell-shaped sepal split into five lobes, and around 20 stamens. Ovary contain two to four locules, with one ovule in each locule. The tree produces high amount of bright, red colored fruits that are small pomes with diameters ranging from , each containing one to four seeds.
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The D function genes were discovered in 1995. These genes are MADS-box proteins and they have a function that is distinct from those previously described, although they have a certain homology with C function genes. These genes are called FLORAL BINDING PROTEIN7 (FBP7) and FLORAL BINDING PROTEIN1L (FBP1l). It was found that, in Petunia, they are involved in the development of the ovule.
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In the dog whelk, the growth of a penis in imposex females gradually blocks the oviduct, although ovule production continues. An imposex female dog whelk passes through several stages of penis growth before it becomes unable to maintain a constant production of ovules. Later stages of imposex lead to sterility and the premature death of the females of reproductive age, which can adversely affect the entire population.
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Individual plants of this species have ovaries with two chambers, each of which contains one ovule. The ovules are located near the base of the flower and are erect, or they are attached horizontally near the base. The style (the structure that connects the ovary to the stigma) is terminal. The stigma can be asymmetrical, bent backwards or downwards, or consist of two lobes.
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Once the ovule has been fertilised, a new sporophyte, protected and nurtured by the female gametophyte, develops and becomes an embryo. When development stops, the embryo becomes dormant, as a seed. Within the embryo are the primordial shoot and root. In angiosperms, as the seed develops after fertilisation, so does the surrounding carpel, its walls thickening or hardening, developing colours or nutrients that attract animals or birds.
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The female gametophyte, the megagametophyte, that participates in double fertilization in angiosperms which is haploid is called the embryo sac. This develops within an ovule, enclosed by the ovary at the base of a carpel. Surrounding the megagametophyte are (one or) two integuments, which form an opening called the micropyle. The megagametophyte, which is usually haploid, originates from the (usually diploid) megaspore mother cell, also called the megasporocyte.
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The pistillate scales are oblong-ovate, three-lobed, pale yellow-green often tinged with red, becoming brown at maturity. These scales bear two or three fertile flowers, each flower consisting of a naked ovary. The ovary is compressed, two-celled, and crowned with two slender styles; the ovule is solitary. Each scale bears a single small, winged nut that is oval, with two persistent stigmas at the apex.
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Some flowering plants supplied the developing embryos for the first stages. The ovule has no stocks and the nutrients are provided by the "mother". In plants, matrotrophy is considered a critical evolutionary development preceding the origin of embryophytes and therefore essential to the evolution of land plants. Matrotrophy is facilitated by cytological and ultrastructural modifications on one or both sides of the generational junction, a region called the placenta.
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The genus Hubera was resolved to be sister to Miliusa, with certain species previously under Polyalthia being additionally reclassified. This reclassification was highly supported by maximum parsimony, Bayesian analysis, and morphological characters. Hubera is characterized by reticulate tertiary venation, axillary inflorescences, 1 ovule per ovary, seeds with flat to slightly raised raphes, and other characters. Hubera's phylogenetic distance and morphological difference from Monoon and Polyalthia, distinguish Hubera on the generic level.
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There may be up to 60 stamens with short filaments with basifixed, elongated anthers. The exine is tectate and reticulate; pistillodes are not present. The pistillate flowers are longer and ovoid with three sepals forming a cup, and three imbricate petals with thick, valvate tips. There are six tiny staminodes with ovoid, uniovulate gynoecium matted in thin brown scales and bearing a three-angled stigma; the ovule is ± pendulous.
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Carpellody is a plant disorder that results in misshapen fruits caused by abnormal development of the ovule-bearing part of the flower in angiosperms. It is commonly called "cat face" and is specific to papayas. Some fruits resemble female fruits, but the disorder can cause severely deformed fruits with deep longitudinal ridges. Fruits are generally more rounded and are unmarketable because of their small size and poor eye appeal.
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The influx of calcium ions arrests tube elongation within 1–2 minutes. At this stage, pollen inhibition is still reversible, and elongation can be resumed by applying certain manipulations, resulting in ovule fertilization. Subsequently, the cytosolic protein p26, a pyrophosphatase, is inhibited by phosphorylation, possibly resulting in arrest of synthesis of molecular building blocks, required for tube elongation. There is depolymerization and reorganization of actin filaments, within the pollen cytoskeleton.
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In plant ovules, the chalaza is located opposite the micropyle opening of the integuments. It is the tissue where the integuments and nucellus are joined. Nutrients from the plant travel through vascular tissue in the funiculus and outer integument through the chalaza into the nucellus. During the development of the embryo sac inside a flowering plant ovule, the three cells at the chalazal end become the antipodal cells.
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Auxin is a hormone related to the elongation and regulation of plants. It also plays an important role in the establishment polarity with the plant embryo. Research has shown that the hypocotyl from both gymnosperms and angiosperms show auxin transport to the root end of the embryo. They hypothesized that the embryonic pattern is regulated by the auxin transport mechanism and the polar positioning of cells within the ovule.
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Next inwards there are numerous stamens, which produce pollen grains, each containing a microscopic male gametophyte. Stamens may be called the "male" parts of a flower and collectively form the androecium. Finally in the middle there are carpels, which at maturity contain one or more ovules, and within each ovule is a tiny female gametophyte. Carpels may be called the "female" parts of a flower and collectively form the gynoecium.
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The fruit of Primulaceae begins as an ovary and inside it are the future seeds (ovules). These are attached to a central axis without any partitions between them (an arrangement called free central placentation; see item 7 in the figure), and they are bitegmic (having a double protective layer around each ovule). Unlike in most other families of Ericales, both layers form the opening at the top (the micropyle).
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She proposed a model for the evolution of the ovule, which remains a likely explanation. She also described the species Cordaites felicis found in coal deposits in England. To adopt the new technique of microscopic anatomy of fossils, she cut sections herself with a gas-powered machine in her garden shed. Her papers are characterised by precise drawings and wash- paintings which are believed to be produced by Benson herself.
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The nucellus (plural: nucelli) is part of the inner structure of the ovule, forming a layer of diploid (sporophytic) cells immediately inside the integuments. It is structurally and functionally equivalent to the megasporangium. In immature ovules, the nucellus contains a megasporocyte (megaspore mother cell), which undergoes sporogenesis via meiosis. In the megasporocyte of Arabidopsis thaliana, meiosis depends on the expression of genes that facilitate DNA repair and homologous recombination.
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Megagametophyte formation of the genera Polygonum and Lilium. Triploid nuclei are shown as ellipses with three white dots. The first three columns show the meiosis of the megaspore, followed by 1-2 mitoses. Ovule with megagametophyte: egg cell (yellow), synergids (orange), central cell with two polar nuclei (bright green), and antipodals (dark green) The haploid megaspore inside the nucellus gives rise to the female gametophyte, called the megagametophyte.
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Hence the term: "double fertilization". This process would result in the production of a seed made of both nutritious tissues and embryo. In gymnosperms, the ovule is not contained in a carpel, but exposed on the surface of a dedicated support organ, such as the scale of a cone, so that the penetration of carpel tissue is unnecessary. Details of the process vary according to the division of gymnosperms in question.
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The number of locules in the ovary is highly variable, usually from two to five, but sometimes as many as fifteen. The placentation is apical, with a pair of ovules hanging by their funicles from the top of each locule. Often, only one of the ovules will develop into a seed. A single, massive obturator may cover the micropyles of both ovules, or each ovule may have its own thin obturator.
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This research is about the molecular phylogeny study between the species like Oxylobium, Gastrolobium, Brachysema, Jansonia, Nemica and podolobium is presented. The study was conducted using the chloroplast DNA and nuclear ribosomal DNA. Oxylobium is shown to be polyphyletic, while Gastrobium is paraphyletic containing within it the genera Branchysema, Jansonia and Nemcia, as well as Oxylobium lineare. Molecular traits such as ovule number, fluroacetate content and different morphological was studied.
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The leaves are opposite, basal 1/3–2/3 connate their length. There is one ovule in each cone that is enclosed by two pairs of cone bracts. Pollen cones, consist of three or four pairs of decussate scales with broad margin, are oblong-spherical shaped, sessile or subsessile at nodes and paired or rarely solitary. Bracts of pollen cones are in two to four pairs, 1/2 connate their length.
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However, there is a strong possibility that this reconstruction was based on the chance finds of ovules having been preserved just lying on a piece of pinna rather than in organic attachment to it. A number of cases are now coming to light that suggest that the seeds were borne in clusters on relatively slender, branching axes, and that these trusses of ovules would have been produced from the top of the trunk among the crown of fronds. The seed megaspore was surrounded by two layers of tissue: a vascularised nucellus and a usually three-layered integument; the nucellus and integument were completely free except at the base of the ovule. There has been some debate as to the exact homologies of these tissues, and it has been argued that the vascularised nucellus was in fact the nucellus and integument that have become fused together, and that the 'integument' was homologous to a cupule that contained only one ovule.
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The pollen grains are dispersed by the wind to the female, ovulate cone that is made up of many overlapping scales (sporophylls, and thus megasporophylls), each protecting two ovules, each of which consists of a megasporangium (the nucellus) wrapped in two layers of tissue, the integument and the cupule, that were derived from highly modified branches of ancestral gymnosperms. When a pollen grain lands close enough to the tip of an ovule, it is drawn in through the micropyle ( a pore in the integuments covering the tip of the ovule) often by means of a drop of liquid known as a pollination drop. The pollen enters a pollen chamber close to the nucellus, and there it may wait for a year before it germinates and forms a pollen tube that grows through the wall of the megasporangium (=nucellus) where fertilisation takes place. During this time, the megaspore mother cell divides by meiosis to form four haploid cells, three of which degenerate.
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Angiosperm life cycle Double fertilization refers to a process in which two sperm cells fertilize cells in the ovule. This process begins when a pollen grain adheres to the stigma of the pistil (female reproductive structure), germinates, and grows a long pollen tube. While this pollen tube is growing, a haploid generative cell travels down the tube behind the tube nucleus. The generative cell divides by mitosis to produce two haploid (n) sperm cells.
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Plants in the genus Pimelea are herbs or small shrubs usually with leaves arranged in opposite pairs. The leaves are usually paler on the lower surface and the petiole is usually very short. The flowers are usually arranged in groups on the ends of the branches and have no petals but four petal-like sepals and two stamens. The ovary has a single ovule and the fruit is usually a nut containing a single seed.
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Hans Melchior (1964) placed Cecropia in the Urticales and Moraceae (Concephaleideae) because of its woody bark.Engler 1964 Later based on the floral characters, most notably the basal ovule and gynoecium, which appears to be formed from a single carpel, Thorne (1976) moved it to the Malvanae- Urticales, family Urticaceae.Thorne (1976) Berg (1978), however, placed it in its own family Cercropiaceae. When phylogenetic data became available, Cecropia was then moved back into the Urticaceae.
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Plant embryogenesis is a process that occurs after the fertilization of an ovule to produce a fully developed plant embryo. This is a pertinent stage in the plant life cycle that is followed by dormancy and germination. The zygote produced after fertilization must undergo various cellular divisions and differentiations to become a mature embryo. An end stage embryo has five major components including the shoot apical meristem, hypocotyl, root meristem, root cap, and cotyledons.
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Metavirus is a genus of viruses in the family Metaviridae. They are retrotransposons that invade a eukaryotic host genome and may only replicate once the virus has infected the host. These genetic elements exist to infect and replicate in their host genome and are derived from ancestral elements unrelated from their host. Metavirus may use several different hosts for transmission, and has been found to be transmissible through ovule and pollen of some plants.
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The flowers of Plagiobothrys nothofulvus generally bloom from February – April. As in many other members of the family Boraginaceae, the flower consists of five petals and are bisexual with both male and female parts represented in the flower. Bees and butterflies are the main pollinators transferring the haploid microgametophyte, or pollen grain, to the pistil. The microgametophyte will then travel down the pistil to the ovule to fertilize the haploid macrogametophyte, or egg.
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Once the pollen tube reaches an ovule, it bursts to deliver the two sperm cells. One of the sperm cells fertilizes the egg cell which develops into an embryo, which will become the future plant. The other one fuses with both polar nuclei of the central cell to form the endosperm, which serves as the embryo's food supply. Finally, the ovary will develop into a fruit and the ovules will develop into seeds.
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In botany the senses are similar to those in zoology, referring to the covering of an organ. When the context indicates nothing to the contrary, the word commonly refers to an envelope covering the ovule. The integument may consist of one layer (unitegmic) or two layers (bitegmic), each of which consisting of two or more layers of cells. The integument is perforated by a pore, the micropyle, through which the pollen tube can enter.
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The ovary is entire, with two loculi, though they are not always well separated. There is a single, erect ovule in each loculus; the style is terete and the stigma simple, though sometimes slightly bifid at the tip. The fruit is oblong, enclosed in the calyx. Corresponding to the structure of the ovary, the fruit is generally two-lobed and two-locular, but sometimes by abortion, there may be only one locule and one seed.
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The male waltzing fly would then propel himself onto the female's back and rubs the female's abdomen. Then, he places his ejaculate into the female's ovule, after which the female ingests the ejaculate. The ejaculate contains sperm and fluids from accessory glands. The evolutionary benefit of the female ingesting the male's ejaculate is unclear, though studies found female waltzing flies that ingested ejaculate has had higher fitness than flies that were prevented from ingesting ejaculate.
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Sexual reproduction in flowering plants involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in stamens, and is carried to the pistil, which has the ovary at its base where fertilization can take place. Within each pollen grain is a male gametophyte which consists of only three cells. In most flowering plants the female gametophyte within the ovule consists of only seven cells.
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Within the ovary, each ovule is born by a placenta or arises as a continuation of the floral apex. The placentas often occur in distinct lines called lines of placentation. In monocarpous or apocarpous gynoecia, there is typically a single line of placentation in each ovary. In syncarpous gynoecia, the lines of placentation can be regularly spaced along the wall of the ovary (parietal placentation), or near the center of the ovary.
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Novon 3(4):418-422. The wood of Ruptiliocarpon was different from the wood of all others to which it was compared in having vestured pits on the walls of its xylem cells. Another study found some similarities in flower structure with Meliaceae, but also found that ovule and seed morphology suggested a relationship with Phyllanthaceae, a family that the authors did not consider to be separate from Euphorbiaceae.Hiroshi Tobe and Barry E. Hammel (1993).
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Grafting, 1870, by Winslow Homer an example of grafting. Fruit tree propagation is usually carried out vegetatively (non-sexually) by grafting or budding a desired variety onto a suitable rootstock. Perennial plants can be propagated either by sexual or vegetative means. Sexual reproduction begins when a male germ cell (pollen) from one flower fertilises a female germ cell (ovule, incipient seed) of the same species, initiating the development of a fruit containing seeds.
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Within the carpel the megasporangium form the ovules, with its protective layers (integument) in the megaspore, and the female gametophyte. Unlike the male gametophyte, which is transported in the pollen, the female gametophyte remains within the ovule. Most flowers have both male and female organs, and hence are considered bisexual (perfect), which is thought to be the ancestral state. However, others have either one or the other and are therefore unisexual, or imperfect.
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This fertile window varies from woman to woman, just as the ovulation date often varies from cycle to cycle for the same woman. The ovule is usually capable of being fertilized for up to 48 hours after it is released from the ovary. Sperm survive inside the uterus between 48 and 72 hours on average, with the maximum being 120 hours (5 days). These periods and intervals are important factors for couples using the rhythm method of contraception.
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Studies have reported evidence against LSI and have proposed alternative explanation. For example, some species that are expected to have LSI display abortion at various stages of seed development, indicating that the abortion was due to selective embryo abortion caused by early-acting inbreeding depression. Another explanation for LSI is that it is the occurrence of gametophytic self-incompatibility, but self-pollen tubes are slowed to the point where they do not achieve fertilization prior to ovule abortion.
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The flagella/cilia apparatus pulls the body of the sperm forwards. The sperm have only a tiny distance to travel to the archegonia, of which there are usually two or three. Two sperm are produced, one of which successfully fertilizes the ovule. Although it is widely held that fertilization of ginkgo seeds occurs just before or after they fall in early autumn, embryos ordinarily occur in seeds just before and after they drop from the tree.
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Each flower has a hairy calyx with yellow glands, the five lobes of which are longer than the inconspicuous petals. There are five stamens surrounding the stigma and style and two fused carpels. The flowers open in succession from the base of the strig and are mostly insect pollinated, but some pollen is distributed by the wind. A pollen grain landing on a stigma will germinate and send a slender pollen tube down the style to the ovule.
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He spent weeks boiling fruits in different solutions to try to make them resemble their living states. He proposed that the fruits contained a stigma with a funnel shaped opening in the center in which the pollen grains would get lodged. The entire pollen grain would not be able to enter into the ovule, a defining trait in angiosperms. This theory was disproved 1933 by Thomas' student Tom Harris, who studied the same reproductive organs and found different results.
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"Most of the fruits were obtained by dissolving in hydrofluoric acid a single very small fragment of shale collected from Cape Stewart" The maceration of the fruits dissolves the main cells wall and leave the cuticle and interior cell organs. This allowed Harris to look closely at the ovules located inside. Upon close inspection of the ovule, whole pollen grains were found inside the micropylar canal. This is typical of a gymnosperm reproduction, not an angiosperm.
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Each carpel in Ranunculus species is an achene that produces one ovule, which when fertilized becomes a seed. If the carpel contains more than one seed, as in Eranthis hyemalis, it is called a follicle. Two or more carpels may be fused together to varying degrees and the entire structure, including the fused styles and stigmas may be called a pistil. The lower part of the pistil, where the ovules are produced, is called the ovary.
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Many insects and some mites are specialized to feed on pollen, and are called palynivores. In non-flowering seed plants, pollen germinates in the pollen chamber, located beneath the micropyle, underneath the integuments of the ovule. A pollen tube is produced, which grows into the nucellus to provide nutrients for the developing sperm cells. Sperm cells of Pinophyta and Gnetophyta are without flagella, and are carried by the pollen tube, while those of Cycadophyta and Ginkgophyta have many flagella.
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The remnants of the megasporangium tissue (the nucellus) surround the megagametophyte. Megagametophytes produce archegonia (lost in some groups such as flowering plants), which produce egg cells. After fertilization, the ovule contains a diploid zygote and then, after cell division begins, an embryo of the next sporophyte generation. In flowering plants, a second sperm nucleus fuses with other nuclei in the megagametophyte forming a typically polyploid (often triploid) endosperm tissue, which serves as nourishment for the young sporophyte.
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This is the most common cause of anovulation and is thought to account for about 70% of all cases. About half the women with hormonal imbalances do not produce enough follicles to ensure the development of an ovule, possibly due to poor hormonal secretions from the pituitary gland or the hypothalamus. The pituitary gland controls most other hormonal glands in the human body. Therefore, any pituitary malfunctioning affects other glands under its influence, including the ovaries.
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This structure rapidly descends down the length of the style via tip-directed growth, reaching rates of 1cm/h, whilst carrying two non-motile sperm cells. Upon reaching the ovule the pollen tube ruptures, thereby delivering the sperm cells to the female gametophyte, ultimately resulting in a double fertilization event. The first fertilization event produces a diploid zygote and the second fertilization event produces a triploid endosperm. Pollen tubes are produced by the male gametophytes of seed plants.
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Increasing the opportunity for paternity by distributing pollen among pollinators may take different routes in different systems, and any of these possibilities can be viewed in a sexual selection context . The gynoecium is also affected by sexual selection. Every part from the ovaries, styles, stigma, and carpels can be faced with the pressures of sexual selection. In ovule packaging, the intensity of pollen competition depends in part on the number of pollen grains relative to the number of ovules.
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The fruits have an ovoid to ovoid-conical shape, ranging between to in size. The smaller, less mature fruits show the distinct structuring of styles and perianth. The styles have flared tips and are short, while the perianth has distinct lobes that are closely placed to the styles. As is typical for acorns of section Quercus, the youngest specimens still have the aborted second ovule and dividing septum present near the base of the developing fruit.
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The seeds are pale to medium brown, ovate, oval, elliptic, elliptical at 5 mm wide by 2 mm (0.2 by 0.08 in). The margin is revolute towards the hilar side. In other words, the edge of the seed is rolled backward from the margins to the undersurface on the scarred side of the seed from a stalk connecting an ovule or a seed with the placenta. The testa, the often thick or hard outer coat of a seed, is rough.
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The ovule is anatropous in orientation and has two integuments (bitegmic), the micropyle (opening) being formed from the inner integument, while the nucellus is small. The embryo sac or megagametophyte is tetrasporic, in which all four megaspores survive. The style is trilobate to trifid (in 3 parts) and the surface of the stigma is wet. ; Androecium Stamens are six, in two trimerous whorls of three, and diplostemonous (outer whorl of stamens opposite outer tepals and the inner whorl opposite inner tepals).
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Most medullosalean ovules preserved as casts or adpressions show three longitudinal ribs and are assigned to the fossil genus Trigonocarpus. When such ovules are preserved as petrifactions, they are assigned to the fossil genera Pachytesta or Stephanospermum, depending mainly on differences in the apical form of the ovule. Another group of medullosalean seeds, usually associated with parispermacean fronds (see later), have six longitudinal ribs and are referred to as Hexagonocarpus when found as adpressions or casts, and Hexapterospermum when found as petrifactions.
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Presumably pollination was at an early stage of cupule and ovule development, before full inflation of the cupules. While Thomas's original idea led many scientist to believe that Caytoniales may have been angiosperms, Harris's further research disproved this theory. The enclosure of ovules in Caytoniales has nevertheless been considered an early stage in evolution of the angiosperm double integument, and the carpels formed from an elaboration of their stalk (Fig. 5). Other theories for the origin of angiosperms derive them from Glossopteridales (Fig.
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Pollination and fruit formation depend on meiosis. Meiosis is central to the processes by which diploid microspore mother cells within the anther give rise to haploid pollen grains, and megaspore mother cells in ovules that are contained within the ovary give rise to haploid nuclei. Union of haploid nuclei from pollen and ovule (fertilization) can occur either by self- or cross-pollination. Fertilization leads to the formation of a diploid zygote that can then develop into an embryo within the emerging seed.
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After being fertilised, the ovary starts to swell and develop into the fruit. With multi-seeded fruits, multiple grains of pollen are necessary for syngamy with each ovule. The growth of the pollen tube is controlled by the vegetative (or tube) cytoplasm. Hydrolytic enzymes are secreted by the pollen tube that digest the female tissue as the tube grows down the stigma and style; the digested tissue is used as a nutrient source for the pollen tube as it grows.
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The pistil may be made up of one carpel or of several fused carpels (e.g. dicarpel or tricarpel), and therefore the ovary can contain part of one carpel or parts of several fused carpels. Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary, and, for each individual pollen grain, to fertilize one individual ovule. Some wind pollinated flowers have much reduced and modified ovaries.
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Alisma is a genus of flowering plants in the family Alismataceae, members of which are commonly known as water-plantains. The genus consists of aquatic plants with leaves either floating or submerged, found in a variety of still water habitats around the world (nearly worldwide).Kew World Checklist of Selected Plant Families The flowers are hermaphrodite, and are arranged in panicles, racemes, or umbels. Alisma flowers have six stamens, numerous free carpels in a single whorl, each with 1 ovule, and subventral styles.
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Location of ovules inside a Helleborus foetidus flower In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center. The female gametophyte — specifically termed a megagametophyte— is also called the embryo sac in angiosperms. The megagametophyte produces an egg cell for the purpose of fertilization.
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SEM image of pollen tubes growing from Lily pollen grains.A pollen tube is a tubular structure produced by the male gametophyte of seed plants when it germinates. Pollen tube elongation is an integral stage in the plant life cycle. The pollen tube acts as a conduit to transport the male gamete cells from the pollen grain—either from the stigma (in flowering plants) to the ovules at the base of the pistil or directly through ovule tissue in some gymnosperms.
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Two main modes of fertilization are found in gymnosperms. Cycads and Ginkgo have motile sperm that swim directly to the egg inside the ovule, whereas conifers and gnetophytes have sperm that are unable to swim but are conveyed to the egg along a pollen tube. The study of pollination spans many disciplines, such as botany, horticulture, entomology, and ecology. The pollination process as an interaction between flower and pollen vector was first addressed in the 18th century by Christian Konrad Sprengel.
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Unlike most biological groupings, it is difficult to find many common characteristics between all of the members of the gnetophytes. The two common characteristics most commonly used are the presence of enveloping bracts around both the ovules and microsporangia as well as a micropylar projection of the outer membrane of the ovule that produces a pollination droplet,Judd, W.S.; Campbell, C.S.; Kellogg, E.A.; Stevens, P.F.; and Donoghue, M.J. (2008) Plant Systematics: A Phylogenetics Approach. 3rd ed. Sunderland, Massachusetts, USA: Sinauer Associates, Inc.
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Eucalyptus ovularis was first formally described by the botanists Joseph Maiden and William Blakely in 1925 in the Journal and Proceedings of the Royal Society of New South Wales. The specific epithet (ovularis) is from Latin meaning "resembing an ovule". Eucalyptus ovularis is part of the subgenus Symphyomyrtus section Dumaria in a sub-group of nine closely related species called series Ovulares. The rough barked members of this series include E. ovularis, E. aequioperta, E. brachycorys, E. myriadena and E. baudiniana.
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The resin of the Burseraceae is nonallergenic and two ovules per carpel occur, whereas the resin of the Anacardiaceae can be allergenic or poisonous and one ovule per carpel is found. The Burseraceae-Anacardiaceae clade is sister to a robust cluster of three other families, the Sapindaceae-Aceraceae-Hippocastanaceae clade. The Rutaceae-Meliaceae-Simaroubaceae clade is sister to the Burseraceae-Anacardiaceae and Sapindaceae-Aceraceae-Hippocastanaceae clade. The rbcL technique is supported and considered acceptable until other methods become better developed for the analysis.
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In endospermic seeds, there are two distinct regions inside the seed coat, an upper and larger endosperm and a lower smaller embryo. The embryo is the fertilised ovule, an immature plant from which a new plant will grow under proper conditions. The embryo has one cotyledon or seed leaf in monocotyledons, two cotyledons in almost all dicotyledons and two or more in gymnosperms. In the fruit of grains (caryopses) the single monocotyledon is shield shaped and hence called a scutellum.
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The longer filaments are 5.5–6 mm long; and the shorter filaments are about 3 mm long. The ovary is moderately to densely covered with white silky hairs, and has one ovule per cell. Both the style and stigma are 4.5–6 mm long. The fruit is a ball-shaped 5-winged schizocarp (a fruit which splits into individual carpels), the wings of which give rise to the specific epithet of "broad winged", and is 12–18 mm long by 15–21 mm wide.
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Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens (or microsporophylls). The "female" cells called megaspores, which will divide to become the egg cell (megagametogenesis), are contained in the ovule and enclosed in the carpel (or megasporophyll). The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Usually, other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators.
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As the pollen tube grows, it makes its way from the stigma, down the style and into the ovary. Here the pollen tube reaches the micropyle of the ovule and digests its way into one of the synergids, releasing its contents (which include the sperm cells). The synergid that the cells were released into degenerates and one sperm makes its way to fertilize the egg cell, producing a diploid (2n) zygote. The second sperm cell fuses with both central cell nuclei, producing a triploid (3n) cell.
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In warm weather this takes about 48 hours but in cold weather it may take a week, and by that time, the ovule may have passed the stage where it is receptive. If fewer than about 35 ovules are fertilised, the fruit may not be able to develop and will fall prematurely. Frost can damage both unopened and open flowers when the temperature falls below . The flowers at the base of the strig are more protected by the foliage and are less likely to be damaged.
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Marshall and Diggle state that the existence of some kind of non-random seed paternity is, in fact, not in question in flowering plants. How this occurs remains unknown. Pollen choice is one of the possibilities, taking into account that 50% of the pollen grain's haploid genome is expressed during its tube's growth towards the ovule. The apparent preference of the females of certain, particularly bird, species for exaggerated male ornaments, such as the peacock's tail, is not easily reconciled with the concept of koinophilia.
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The natural hybrid D. rotundifolia × D. linearis (conventionally but incorrectly referred to as Drosera ×anglica), is also sterile but is morphologically similar to the modern D. anglica. Errors in meiosis during ovule and pollen production, however, can result in a chromosome doubling which can allow for viable seed to be produced. The resulting plants, known as amphiploids, would be fertile. Woods noted that this appeared to be an ongoing process with D. anglica speciating from D. rotundifolia × D. linearis through amphidiploidy in multiple locations.
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The vegetative cell then produces the pollen tube, a tubular protrusion from the pollen grain, which carries the sperm cells within its cytoplasm. The sperm cells are the male gametes that will join with the egg cell and the central cell in double fertilization. The first fertilization event produces a diploid zygote and the second fertilization event produces a triploid endosperm. The germinated pollen tube must drill its way through the nutrient-rich style and curl to the bottom of the ovary to reach an ovule.
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Mechanism to prevent selfing and allowing compatible pollen to grow a pollen tube for fertilization to take place Once the pollen grain is recognized and hydrated, the pollen grain germinates to grow a pollen tube. There is competition in this step as many pollen grains may compete to reach the egg. The stigma plays a role in guiding the sperm to a receptive ovule, in the case of many ovules. Only compatible pollen grains are allowed to grow as determined by signaling with the stigma.
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The parts begin with a perianth of whorled tepals, with the outer whorls more sepaloid, graduating to more petaloid inner tepals. The stamens are also numerous and in a whorl. The carpels are arranged in a whorl, are separate, and number from 5 to numerous carpels in each whorl, each carpel containing a single ovule. The stem presents nodes unilacunar (with one trace), with internal phloem absent, secondary thickening developing from a conventional cambial ring, xylem with tracheids; The sieve-tube plastids are S-type.
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All others are called secondary sex organs, divided between the external sex organs—the genitals or genitalia, visible at birth in both sexes—and the internal sex organs. Mosses, ferns, and some similar plants have gametangia for reproductive organs, which are part of the gametophyte. The flowers of flowering plants produce pollen and egg cells, but the sex organs themselves are inside the gametophytes within the pollen and the ovule. Coniferous plants likewise produce their sexually reproductive structures within the gametophytes contained within the cones and pollen.
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Araucaria angustifolia cones and nuts Members of the Araucariaceae (Araucaria, Agathis, Wollemia) have the bract and seed scales fully fused, and have only one ovule on each scale. The cones are spherical or nearly so, and large to very large, 5–30 cm diameter, and mature in 18 months; at maturity, they disintegrate to release the seeds. In Agathis, the seeds are winged and separate readily from the seed scale, but in the other two genera, the seed is wingless and fused to the scale.
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In gymnosperms and flowering plants, the megaspore is produced inside the nucleus of the ovule. During megasporogenesis, a diploid precursor cell, the megasporocyte or megaspore mother cell, undergoes meiosis to produce initially four haploid cells (the megaspores). Angiosperms exhibit three patterns of megasporogenesis: monosporic, bisporic, and tetrasporic, also known as the Polygonum type, the Alisma type, and the Drusa type, respectively. The monosporic pattern occurs most frequently (>70% of angiosperms) and is found in many economically and biologically important groups such as Brassicaceae (e.g.
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The genus Lepidothamnus was once part of Dacrydium in the classification by Bentham and Hooker in 1880. However, current taxonomy separates it as a distinct genus with three species, one endemic to southern Chile and the other two in New Zealand. All three species have a distinctive cone morphology not shared with other podocarps with its erect ovule, as well as the absence of resin ducts in the leaves. These three species also synthesise cupressuflavone as their major biflavonoid – a feature not found in other podocarps.
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Although commonly called a fruit, the synconium is botanically an infructescence, a type of multiple fruit. The small fig flowers and later small single-seeded (true) fruits line its interior surface. A small opening or ostiole, visible on the middle of the fruit, is a narrow passage that allows the specialized fig wasp, Blastophaga psenes to enter the inflorescence and pollinate the flowers, after which each fertilized ovule (one per flower, in its ovary) develops into a seed. At maturity, these 'seeds' (actually single-seeded fruits) line the inside of each fig.
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Corn silk is part stigma and part style, providing a female flower surface to which pollen grains can adhere and defining the lengthy path through which the pollen must transmit its genetic material. The stigma is the very tip of the corn silk, which has a larger number of hairs to help pollen to adhere to it. Kernel formation in the cob requires pollination of the external corn silk by wind or insects. Usually several grains of pollen adhere, but only one will successfully participate in fertilization of the ovule to form a corn kernel.
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Corolla- Petals 5, polypetalous but slightly connate below and jointed with the staminal column,twisted. Androecium- Stamens many,monadelphous, arranged on the staminal column; staminal column is shorter than the petals,divided above into numerous filaments, anthers monothecus, reniform, basifixed, filament short, extrorse. Pollen are spherical with spikes, size is approximately 90 microns. Pollen grains of Sida acuta Gynoecium- Carples 5, syncarpous, ovary superior,penta or multilocular with axile placentation, one ovule in each locule; style 1, passing through the staminal tube; stigma globular,correspond to the number of carples.
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Veillon described how the morphology of New Caledonian Araucaria conforms to these models and noticed that species following the Rauh model have bigger leaves. He also designed a key to help in field identification, based on characters fixed in adults, so ecological factors impacting tree morphology won't interfere with identification. New Caledonian Araucaria species belong to the Eutacta section, one of the four sections defined by Wilde and Eames in 1952.Wilde MH, AJ Eames. 1952. The ovule and “seed” of Araucaria bidwillii with discussion of the taxonomy of the genus.
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Following fertilization, the zygote and endosperm are present within the ovule, as seen in stage I of the illustration on this page. Then the zygote undergoes an asymmetric transverse cell division that gives rise to two cells - a small apical cell resting above a large basal cell. These two cells are very different, and give rise to different structures, establishing polarity in the embryo. ;apical cell:The small apical cell is on the top and contains most of the cytoplasm, the aqueous substance found within cells, from the original zygote.
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TTS proteins were also placed on various locations of semi in vevo pollinated pistils, and pollen tubes were observed to immediately extend toward the proteins. Transgenic plants lacking the ability to produce TTS proteins exhibited slower pollen tube growth and reduced fertility. Rupture of pollen tube The rupture of the pollen tube to release sperm in Arabidopsis has been shown to depend on a signal from the female gametophyte. Specific proteins called FER protein kinases present in the ovule control the production of highly reactive derivatives of oxygen called reactive oxygen species (ROS).
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Peter H. Weston and Nigel Barker reviewed the suprageneric relationships of the Proteaceae in 2006, using molecular and morphological data. In this scheme Cenarrhenes is located within the subfamily Proteoideae on account of it having cluster roots, a solitary ovule and indehiscent fruits. In a phylogenetic study including all the Proteaceae genera, it was found that it was most closely related to the genera Beaupreopsis (New Caledonia) and Dilobeia (Madagascar).Sauquet, H., P. H. Weston, C. J. Anderson, N. P. Barker, D. J. Cantrill, A. R. Mast, and Savolainen, V. (2009).
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While working with Mirabilis jalapa, Correns observed that leaf colour was dependent only on the genotype of the maternal parent. Based on these data, he determined that the trait was transmitted through a character present in the cytoplasm of the ovule. Later research by Ruth Sager and others identified DNA present in chloroplasts as being responsible for the unusual inheritance pattern observed. Work on the poky strain of the mould Neurospora crassa begun by Mary and Hershel Mitchell ultimately led to the discovery of genetic material in the mitochondria, the mitochondrial DNA.
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The sex of seedlings can only be determined at the first flowering, which mostly occurs after three years. The male inflorescence is built up of four to six apetalous flowers, while the female inflorescence normally consists of only one apetalous flower and contains one ovary and one ovule. Fertilization occurs solely via wind pollination, which is why male plants need to be planted near the female plants to allow for fertilization and fruit production. The oval or lightly roundish fruits grow in compact grapes varying from pale yellow to dark orange.
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The pollen tube releases two sperm nuclei into the ovule. In gymnosperms, fertilization occurs within the archegonia produced by the female gametophyte. While it is possible that several egg cells are present and fertilized, typically only one zygote will develop into a mature embryo as the resources within the seed are limited. In flowering plants, one sperm nucleus fuses with the egg cell to produce a zygote, the other fuses with the two polar nuclei of the central cell to give rise to the polyploid (typically triploid) endosperm.
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If the gnetophytes are nested within conifers, they must have lost several shared derived characters of the conifers (or these characters must have evolved in parallel in the other two conifer lineages): narrowly triangular leaves (gnetophytes have diverse leaf shapes), resin canals, a tiered proembryo, and flat woody ovuliferous cone scales. These kinds of major morphological changes are not without precedent in the Pinaceae, however: the Taxaceae, for example, have lost the classical cone of the conifers in favor of a single-terminal ovule surrounded by a fleshy aril.
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Equivalent genes were later found in Arabidopsis, where they are also involved in controlling the development of carpels and the ovule and even with structures related to seed dispersal. The appearance of interesting phenotypes in RNA interference studies in Petunia and tomato led, in 1994, to the definition of a new type of function in the floral development model. The E function was initially thought to be only involved in the development of the three innermost verticils, however, subsequent work found that its expression was required in all the floral verticils.
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Rice is used as a model organism for investigating the molecular mechanisms of meiosis and DNA repair in higher plants. Meiosis is a key stage of the sexual cycle in which diploid cells in the ovule (female structure) and the anther (male structure) produce haploid cells that develop further into gametophytes and gametes. So far, 28 meiotic genes of rice have been characterized. Studies of rice gene OsRAD51C showed that this gene is necessary for homologous recombinational repair of DNA, particularly the accurate repair of DNA double-strand breaks during meiosis.
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The megagametophyte typically develops a small number of cells, including two special cells, an egg cell and a binucleate central cell, which are the gametes involved in double fertilization. The central cell, once fertilized by a sperm cell from the pollen becomes the first cell of the endosperm, and the egg cell once fertilized become the zygote that develops into the embryo. The gap in the integuments through which the pollen tube enters to deliver sperm to the egg is called the micropyle. The stalk attaching the ovule to the placenta is called the funiculus.
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The presence of pollen competition when outcrossing occurs in a plant that utilizes self-fertilization allows recognition and selection of different pollen grains to fertilize the ovule. A. thaliana is closely related to Arabidopsis lyrata being that one diverged from the other through speciation. Although speciation has separated these species, they are still capable of providing a means of outcrossing between each other, initiating pollen competition within the plant. Although competition does occur among male gametophytes of both species, A. lyrata has very low instances of adaptive evolution compared to A. thaliana.
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Nageia nagi pollen cones seed cones Nageia nagi is a hardy tree species that can withstand a range of weather conditions, but it prefers moist sites that are well drained and with full sunlight to light shade. Being from the family Podocarpaceae, it is a dioecious tree, that is, the male and female parts of the trees are on separate plants. The pollen cones are catkins and the female cones, which mature in one year, are reduced fleshy bracts that contain a single inverted ovule. It requires wind for pollination; it cannot self- pollinate.
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Attraction is effected by color, scent, and nectar, which may be secreted in some part of the flower. The characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite (having both pollen and ovule producing parts in the same flower structure), flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization. Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot easily transfer pollen to the pistil (receptive part of the carpel).
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As such, the reproductive traits and behaviors of plants suggests the evolution of behaviors and characteristics that increase the genetic relatedness of fertilized eggs in the plant ovary, thereby fostering kin selection and cooperation among the seeds as they develop. These traits differ among plant species. Some species have evolved to have fewer ovules per ovary, commonly one ovule per ovary, thereby decreasing the chance of developing multiple, differently fathered seeds within the same ovary. Multi-ovulated plants have developed mechanisms that increase the chances of all ovules within the ovary being fathered by the same parent.
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A type of incompatibility that is found as often in plants as in animals occurs when the egg or ovule is fertilized but the zygote does not develop, or it develops and the resulting individual has a reduced viability. This is the case for crosses between species of the frog genus, where widely differing results are observed depending upon the species involved. In some crosses there is no segmentation of the zygote (or it may be that the hybrid is extremely non-viable and changes occur from the first mitosis). In others, normal segmentation occurs in the blastula but gastrulation fails.
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The oocytes were fertilized in the archegonia by free-swimming flagellate sperm produced by windborne miniaturized male gametophytes in the form of pre-pollen. The resulting zygote developed into the next sporophyte generation while still retained within the pre-ovule, the single large female meiospore or megaspore contained in the modified sporangium or nucellus of the parent sporophyte. The evolution of heterospory and endospory were among the earliest steps in the evolution of seeds of the kind produced by gymnosperms and angiosperms today. The rRNA genes seems to escape global methylation machinery in bryophytes, unlike seed plants.
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It consists of one carpel and contains a single pendulous ovule. At the base of the ovary are four linear or awl-shaped scales of long that secrete a copious amount of nectar. The indehiscent fruit consists of one cavity, containing one oval to globe-shaped seed of long, with a broad indent where it was attached, hairless or covered with a fine powder and generally partially covered by a pale elaiosome. The sixteen Leucospermum species that have been analysed are all diploids having twelve sets of homologue chromosomes (2n=24), which is consistent with the rest of the subtribe Proteinae.
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Longitudinal section of female flower of squash showing pistil (=ovary+style+stigma), ovules, and petals. The petals and sepals are above the ovary; such a flower is said to have an inferior ovary, or the flower is said to be epigynous. Cross section of Tulip ovary In the flowering plants, an ovary is a part of the female reproductive organ of the flower or gynoecium. Specifically, it is the part of the pistil which holds the ovule(s) and is located above or below or at the point of connection with the base of the petals and sepals.
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One of the paths leads to the ovule Piddi, meaning Mandragora or Mandrake in Sards; this poisonous plant grows all over the Supramonte. Helped by the locals, Verin and Cicalò built a network of mule tracks that, with a series of bends, pass through the most impervious gullies and lead to the sea, which can be seen only in Cala Sisine; here there are docks built to transport charcoal and woods. From Cala Sisine it is possible to return to the starting point by the sea with an inflatable boat or by land with a SUV.
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Malveae species are primarily found in the Americas, although genera within the tribe are also found in Eurasia, Australia, and Africa. The intergeneric relationships within Malveae are not well resolved. The tribe was originally split between Eumalveae, Malopeae, Sideae and Abutileae based on carpel arrangement, ovule numbers and the flowers' stigmatic arrangements, however, now Malveae is generally grouped into 14 alliances (Abutilon, Batesimalva, Kearnemalvastrum, Malvastrum, Sphaeralcea, Modiola, Anoda, Gaya, Malope, Anisodontea, Malva, Sidalcea, Malacothamnus and Plagianthus). Recent ribosomal sequencing, however, suggests that these alliances are non monophyletic and may be better characterized by the presence or absence of involucre bracts (i.e.
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He now tackled the chapter of Variation setting out his hypothesis about heredity, that "pangenesis" brought "gemmules" from every cell of the body to the reproductive organs, where they formed the "true ovule or bud" that could pass on traits to the next generation. Huxley was dubious, cautiously writing "Somebody rummaging among your papers half a century hence will find Pangenesis and say, 'See this wonderful anticipation of our modern theories, and that stupid ass Huxley prevented his publishing them." Times were changing. Lyell became embroiled in a row for having incorporated into Antiquity of Man whole paragraphs of a paper by Lubbock.
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When pollination occurs between species it can produce hybrid offspring in nature and in plant breeding work. In angiosperms, after the pollen grain (gametophyte) has landed on the stigma, it germinates and develops a pollen tube which grows down the style until it reaches an ovary. Its two gametes travel down the tube to where the gametophyte(s) containing the female gametes are held within the carpel. After entering an ovum cell through the micropyle, one male nucleus fuses with the polar bodies to produce the endosperm tissues, while the other fuses with the ovule to produce the embryo.
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In the latter case, separate terms are used depending on whether or not the ovary is divided into separate locules. If the ovary is divided, with the ovules born on a line of placentation at the inner angle of each locule, this is axile placentation. An ovary with free central placentation, on the other hand, consists of a single compartment without septae and the ovules are attached to a central column that arises directly from the floral apex (axis). In some cases a single ovule is attached to the bottom or top of the locule (basal or apical placentation, respectively).
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ARY Film trophy is known as ARY Film Award of Merit and recently it is also referred as AFA's trophy. It is Made of gold-plated britannium on a black metal base, it is 11 in (27.94 cm) tall, weighs 6.5 lb (2.94 kg) and depicts a gold-lady rendered in Art Deco style turned into curve style making ovule shape above her head by joining hands standing on a reel of film with presenter's name. The presenter name represent organization logo and respective winner field and name. As of first ceremony a total of 33 AFA's trophies have been presented to artists.
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However, the need for accurate and detailed plant descriptions meant that some herbals were more botanical than medicinal. German Otto Brunfels's (1464–1534) Herbarum Vivae Icones (1530) contained descriptions of about 47 species new to science combined with accurate illustrations. His fellow countryman Hieronymus Bock's (1498–1554) Kreutterbuch of 1539 described plants he found in nearby woods and fields and these were illustrated in the 1546 edition. However, it was Valerius Cordus (1515–1544) who pioneered the formal botanical description that detailed both flowers and fruits, some anatomy including the number of chambers in the ovary, and the type of ovule placentation.
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Nuclear movement also occurs in response to mechanical stimulation. The nuclei of cultured ovule parenchyma tobacco cells were found to move directly to the site of probing by a fine glass pipette via cytoplasmic strands, which contain actin filaments specialized to carry out cytoplasmic streaming. This is likely a response co- opted from cytoplasmic streaming, but a receptor or other downstream signaling components underlying this cellular response have not been identified. Nonetheless mechanical stimulation is a potent signal resulting in nuclear movement, and suggests that nuclear movement may be a process important for integration of mechanical stimulation during thigmotropism, gravitropism, or cellular interactions during development.
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Venn diagram representing the relationship between (culinary) vegetables and botanical fruits Many common terms for seeds and fruit do not correspond to the botanical classifications. In culinary terminology, a fruit is usually any sweet-tasting plant part, especially a botanical fruit; a nut is any hard, oily, and shelled plant product; and a vegetable is any savory or less sweet plant product.For a Supreme Court of the United States ruling on the matter, see Nix v. Hedden. However, in botany, a fruit is the ripened ovary or carpel that contains seeds, a nut is a type of fruit and not a seed, and a seed is a ripened ovule.
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The epithet bidwillii is in honor of John Carne Bidwill (1815-1853) who was an Australian botanist born in England and became the first director of the Royal Botanic Gardens, Sydney. However, H. bidwilli did not always identify with its current name. Kirk first discovered the species in 1877 under the name Dacrydium bidwillii, a name that is still presently used at times to reference the species, and this naming was suggested by Sir Joseph Hooker. It wasn’t until 1982 when C.J. Quinn proposed an alternative taxonomy for the species based on ovule morphology and orientation, that the species obtained the current scientific name of Halocarpus bidwillii.
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Elongation of a corn silk strand stops soon after a grain of pollen is captured, or due to senescence of the silk 10 days after its emergence. If an ovule is successfully fertilized, the corn silk will detach from it two or three days later. Otherwise, the silk will remain attached indefinitely, and fertilization remains possible (with decreasing chances of success) for 10 days after silk emergence. For this reason, it is possible to sample developing ears of corn from a field, husking them gently with a sharp knife, then shaking them to assess the progress of pollination based on how much of the corn silk falls away.
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In June 1997 Animesh Ray suggested that gametophyte is responsible for pollen tube guidance but also mentioned that it might be indirectly accomplished. In 2002 he studied ovule of Arabidopsis thaliana and discovered a new type of gene regulation, involving post-transcriptional gene silencing, through a gene called DCL1 which is required for RNA silencing all multicellular organisms, including plants, in Drosophila and Caenorhabditis. In 2007 he and his students used Arabidopsis thaliana to track a footprint of broken DNA and suggested that the genes move from one locus to another. In 2011 he suggested that microRNA gene, miR-34b can be of use to diagnose melanoma.
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He describes the standard arrangement in angiosperms—the nucellus joined by the chalaza to the integuments, which surround the nucellus except at the micropyle, through which the pollen tubes enter. David Mabberley describes this section as "a remarkably clear exposition of one of the most intricate and misunderstood areas of developmental anatomy in higher plants." The third part is a discussion of the "female flower" of cycads and conifers. In it, Brown sets out for the first time the fundamental difference between angiosperms and gymnosperms; namely, that pollen grains are drawn into the ovule in gymnosperms, whereas in angiosperms, contact is via pollen tubes.
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After rediscovering Mendel's laws of heredity, which can be explained with chromosomal inheritance, he undertook experiments with the four o'clock plant Mirabilis jalapa to investigate apparent counterexamples to Mendel's laws in the heredity of variegated (green and white mottled) leaf color. Correns found that, while Mendelian traits behave independently of the sex of the source parent, leaf color depended greatly on which parent had which trait. For instance, pollinating an ovule from a white branch with pollen from another white area resulted in white progeny, the predicted result for a recessive gene. Green pollen used on a green stigma resulted in all green progeny, the expected result for a dominant gene.
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Synapomorphies of Opuntioideae include small deciduous, barbed spines called glochids born on areoles and a bony aril surrounding a campylotropous ovule (inverted and curved, such that the micropyle almost meets the funiculus). Other prominent morphological characters for this subfamily are presence of cylindrical, caducous leaves that tend to be shed by maturity and the sectioning of the stem into joints or pads known as cladodes. Opuntioideae are unique among cacti for lacking in the stem a thick cortex, an extensive system of cortical bundles, collapsible cortical cells, and medullary bundles. Typically, the epidermis consists of a single layer of irregularly shaped cells, a cuticle at least 1-2 microns thick, and long, uniseriate trichomes in the areoles.
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The stamens have thread-like filaments are connected to a rim formed on the base of the tepals (epitepalous), after anthesis the filaments elongate up to 1.5mm in length. The anthers are 0.6 to 0.7mm long by 0.5mm wide, and are divided for about half of their length. The semi-inferior, sharply tapered ovary is not attached to anything for part of its length, or is described as fused with the perianth on its lower, ovule- bearing part, with the upper part forming a slender column or cone, approximately 1mm in length. The three (rarely two or four) stigmas are filiform, and are 0.7 to 1.2mm in length, but can exceptionally be 1.5 to 2mm long.
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It has been observed that in sea urchins of the genus Strongylocentrotus the concentration of spermatocytes that allow 100% fertilization of the ovules of the same species is only able to fertilize 1.5% of the ovules of other species. This inability to produce hybrid offspring, despite the fact that the gametes are found at the same time and in the same place, is due to a phenomenon known as gamete incompatibility, which is often found between marine invertebrates, and whose physiological causes are not fully understood. In some Drosophila crosses, the swelling of the female's vagina has been noted following insemination. This has the effect of consequently preventing the fertilization of the ovule by sperm of a different species.
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Such a change in circumscription could result in an expansion of the range of plant parts and/or preservation states that can be incorporated within the taxon. For instance, a fossil-genus originally based on compressions of ovules could be used to include the multi- ovulate cupules within which the ovules were originally borne. A complication can arise if, in this case, there was an already named fossil-genus for these cupules. If palaeobotanists were confident that the type of the ovule fossil- genus and of the cupule fossil-genus could be included in the same genus, then the two names would compete as to being the correct one for the newly emended genus.
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Plants exhibiting selfing syndrome are typically autogamous and display reduced pollen ovule (P/O) ratios, resulting in a smaller pollen count and a larger number of ovules. The reduction of flower size has been studied between the selfing species Capsella rubella and its closely related outcrossing relative Capsella grandiflora. The petals between the two species grow at the same rate, however, a decrease in the sterile apetela (SAP) protein activity due to variation in the SAP intron in C. rubella is responsible for reduced petal size. This is due to the smaller number of cells present in the petal and results in petals that are around 35% smaller than the petals of C. grandiflora.
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Functional domains of the floral regulator AGAMOUS: characterization of the DNA binding domain and analysis of dominant negative mutations. Mizukami, Y., Huang, H., Tudor, M., Hu, Y., Ma, H. Plant Cell (1996) AP2 also makes up another compound called ANT, which is composed of two AP2 domains homologous with the DNA binding domain of ethylene response element binding proteins.The AINTEGUMENTA gene of Arabidopsis required for ovule and female gametophyte development is related to the floral homeotic gene APETALA2. Klucher, K.M., Chow, H., Reiser, L., Fischer, R.L. Plant Cell (1996) Another study by Maes, T. titled Petunia Ap2-like genes and their role in flower and seed development, discovered three AP2-like proteins from petunia and by studying their expression patterns in situ hybridization: PhAP2A, PhAP2B, and PhAP2C.
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Selective embryo abortion (also known as selective seed abortion and selective ovule abortion ), is a form of non-random, premature termination of embryonic development in plants. Selective embryo abortion assumes that embryo termination depends on the genetic quality of seeds developing within an ovary, and predicts that successfully matured seeds will be of greater fitness than aborted seeds. Consequently, selective embryo abortion has the potential to act as a unique stage of natural selection, influencing the evolution of plant populations and species. This concept was described by botanist John T. Buchholz in 1922 under his framework of developmental selection, which referred to selective embryo abortion as “interovular selection.” Selective embryo abortion may result from competition among embryos for maternal resources.
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Function D specifies the identity of the ovule, as a separate reproductive function from the development of the carpels, which occurs after their determination. Function E relates to a physiological requirement that is a characteristic of all floral verticils, although, it was initially described as necessary for the development of the three innermost verticils (Function E sensu stricto). However, its broader definition (sensu lato) suggests that it is required in the four verticils. Therefore, when Function D is lost the structure of the ovules becomes similar to that of leaves and when Function E is lost sensu stricto, the floral organs of the three outer most verticils are transformed into sepals, while on losing Function E sensu lato, all the verticils are similar to leaves.
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One major impediment to breeding bananas is polyploidy; Gros Michel and Cavendish bananas are triploid and thus attempts at meiosis in the plant's ovules cannot produce a viable gamete. Only rarely does the first reduction division in meiosis in the plants' flowers tidily fail completely, resulting in a euploid triploid ovule, which can be fertilized by normal haploid pollen from a diploid banana variety; a whole stem of bananas would contain only a few seeds and sometimes none. As a result, the resulting new banana variety is tetraploid, and thus contains seeds; the market for bananas is not accustomed to bananas with seeds. Experience showed that where both meiosis steps failed, causing a heptaploid seedling, or when the seedling is aneuploid, results are not as good.
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Pherosphaera hookeriana is a densely-branched erect shrub or small tree growing to heights of 5 meters, branches are often small and rigid with leaves arranged spirally and fully appressed to the stem. Individual leaves can measure up to 1.5 millimetres (mm) long, and 1 mm wide, leaves are thick, blunt and concave with a rounded keel. Male flowers in compressed, terminal globular cones, ranging from 1–5 mm in diameter, with 8 to 15 fertile scales, each scale has two pollen sacs on the abaxial surface. Female flowers occur in cones on short branches that usually droop (hence the old common name) flowers are globular ranging from 2–4 mm long and have 3-8 fertile scales, with a single ovule on the upper surface of each scale.
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When placed on the stigma of a flowering plant, under favorable circumstances, a pollen grain puts forth a pollen tube, which grows down the tissue of the style to the ovary, and makes its way along the placenta, guided by projections or hairs, to the micropyle of an ovule. The nucleus of the tube cell has meanwhile passed into the tube, as does also the generative nucleus, which divides (if it hasn't already) to form two sperm cells. The sperm cells are carried to their destination in the tip of the pollen tube. Double-strand breaks in DNA that arise during pollen tube growth appear to be efficiently repaired in the generative cell that carries the male genomic information to be passed on to the next plant generation.
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Experimental warming has been shown to start flowering substantially earlier than control cushions experiencing ambient temperature. Both the male and female phases developed faster in the OTCs and capsules (fruits) matured earlier, and the cushions produced more mature seeds and had a higher seed/ovule ratio contributing to an overall positive reproductive response. However, a study on four populations across a latitudinal gradient in North America showed that southern populations of moss campion had lower survival and recruitment, but higher individual growth rates than more northern populations. Furthermore, vital rates such as growth, survival, and fruits per area were shown to increase in moderately warmer years yet declined in the very warmest years, suggesting that a change in climate into warmer conditions or more frequent unusually warm summers may eventually lead to negative impacts.
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Self-incompatibility (SI) is a general name for several genetic mechanisms in angiosperms, which prevent self-fertilization and thus encourage outcross and allogamy. It should not be confused with genetically controlled physical or temporal mechanisms that prevent self-pollination, such as heterostyly and sequential hermaphroditism (dichogamy). In plants with SI, when a pollen grain produced in a plant reaches a stigma of the same plant or another plant with a matching allele or genotype, the process of pollen germination, pollen-tube growth, ovule fertilization and embryo development is halted at one of its stages and consequently no seeds are produced. SI is one of the most important means of preventing inbreeding and promoting the generation of new genotypes in plants, and it is considered as one of the causes for the spread and success of angiosperms on the earth.
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Botanical illustration The flowers are creamy white, 9 mm diameter; the calyx is urn-shaped, five-toothed, persistent; the corolla is five-lobed, with rounded lobes, imbricate in bud; the five stamens alternate with the corolla lobes, the filaments slender, the anthers pale yellow, oblong, two-celled, the cells opening longitudinally; the ovary is inferior, one-celled, with a thick, pale green style and a flat stigma and a single ovule. The flowers are borne in flat-topped cymes 10 cm in diameter in mid to late spring. The fruit is a drupe 1 cm long, dark blue-black with glaucous bloom, hangs until winter, becomes edible after being frosted, then eaten by birds; the stone is flat and even, broadly oval. Wherever it lives, black haw prefers sunny woodland with well-drained soil and adequate water.
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The term spore derives from the ancient Greek word σπορά spora, meaning "seed, sowing", related to σπόρος sporos, "sowing", and σπείρειν speirein, "to sow". In common parlance, the difference between a "spore" and a "gamete" is that a spore will germinate and develop into a sporeling, while a gamete needs to combine with another gamete to form a zygote before developing further. The main difference between spores and seeds as dispersal units is that spores are unicellular, the first cell of a gametophyte, while seeds contain within them a developing embryo (the multicellular sporophyte of the next generation), produced by the fusion of the male gamete of the pollen tube with the female gamete formed by the megagametophyte within the ovule. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes.
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Similar results are observed in mosquitoes of the genus Culex, but the differences are seen between reciprocal crosses, from which it is concluded that the same effect occurs in the interaction between the genes of the cell nucleus (inherited from both parents) as occurs in the genes of the cytoplasmic organelles which are inherited solely from the female progenitor through the cytoplasm of the ovule. In Angiosperms, the successful development of the embryo depends on the normal functioning of its endosperm. The failure of endosperm development and its subsequent abortion has been observed in many interploidal crosses (that is, those between populations with a particular degree of intra or interspecific ploidy), and in certain crosses in species with the same level of ploidy. The collapse of the endosperm, and the subsequent abortion of the hybrid embryo is one of the most common post-fertilization reproductive isolation mechanism found in angiosperms.
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During pollen tube growth towards the ovary, the generative nucleus divides to produce two separate sperm nuclei (haploid number of chromosomes) – a growing pollen tube therefore contains three separate nuclei, two sperm and one tube. The sperms are interconnected and dimorphic, the large one, in a number of plants, is also linked to the tube nucleus and the interconnected sperm and the tube nucleus form the "male germ unit". Double fertilisation is the process in angiosperms (flowering plants) in which two sperm from each pollen tube fertilise two cells in a female gametophyte (sometimes called an embryo sac) that is inside an ovule. After the pollen tube enters the gametophyte, the pollen tube nucleus disintegrates and the two sperm cells are released; one of the two sperm cells fertilises the egg cell (at the bottom of the gametophyte near the micropyle), forming a diploid (2n) zygote.
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Tulip anther with many grains of pollen Closeup image of a cactus flower and its stamens Scanning electron microscope image (500x magnification) of pollen grains from a variety of common plants: sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), prairie hollyhock (Sidalcea malviflora'’), oriental lily (Lilium auratum), evening primrose (Oenothera fruticosa), and castor bean (Ricinus communis). Pollen is a powdery substance consisting of pollen grains which are male microgametophytes of seed plants, which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male cone to the female cone of coniferous plants. If pollen lands on a compatible pistil or female cone, it germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte.
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Character and description of Kingia was first published in 1826 as an appendix to the second volume of Phillip Parker King's Narrative of a survey of the intertropical and western coasts of Australia performed between the years 1818 and 1822. Character and description of Kingia, a new genus of plants found on the south-west coast of New Holland, with observations on the structure of its unimpregnated ovulum, and on the female flower of Cycadeae and Coniferae is an 1826 paper by botanist Robert Brown. Though nominally a formal description of the then-unpublished genus Kingia, it is more notable for its digressions into ovule anatomy and development, in which Brown sets out for the first time the modern understanding of the structure of angiosperm ovules, and publishes the first description of the fundamental difference between angiosperms and gymnosperms. Of the latter it has been said that "no more important discovery was ever made in the domain of comparative morphology and systematic Botany".
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