"Stamen The stamen (plural ""stamina"" or ""stamens"") is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium. A stamen typically consists of a stalk called the filament and an anther which contains ""microsporangia"". Most commonly anthers are two-lobed and are attached to the filament either at the base or in the middle area of the anther. The sterile tissue between the lobes is called the connective. A pollen grain develops from a microspore in the microsporangium and contains the male gametophyte. The stamens in a flower are collectively called the androecium. The androecium can consist of"
"Gynoecium Gynoecium (, from Ancient Greek , ""gyne"", meaning ""woman"", and , ""oikos"", meaning ""house"") is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower, it consists of (one or more) pistils and is typically surrounded by the pollen-producing reproductive organs, the stamens, collectively called the androecium. The gynoecium is often referred to as the ""female"" portion of the flower, although rather than directly producing female gametes (i.e. egg cells), the gynoecium produces megaspores, each of"
"pollen of visiting insects or by various hairs, flaps, or sculpturings. The style and stigma of the flower are involved in most types of self incompatibility reactions. Self-incompatibility, if present, prevents fertilization by pollen from the same plant or from genetically similar plants, and ensures outcrossing. Gynoecium Gynoecium (, from Ancient Greek , ""gyne"", meaning ""woman"", and , ""oikos"", meaning ""house"") is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower, it consists of (one or"
"holding the whole inflorescence is called a peduncle and the major axis (incorrectly referred to as the main stem) holding the flowers or more branches within the inflorescence is called the rachis. The stalk of each single flower is called a pedicel. A flower that is not part of an inflorescence is called a solitary flower and its stalk is also referred to as a peduncle. Any flower in an inflorescence may be referred to as a floret, especially when the individual flowers are particularly small and borne in a tight cluster, such as in a pseudanthium. The fruiting stage"
"stamens). Staminodes can alternate with the fertile stamens or they can all occur in the upper or lower hemisphere of the flower. The stalks of the stamens are bearded in many genera, although in some of these only some are bearded while others are hairless. Sometimes one to three stamens are absent altogether. Pollen is usually released from slits that open on the sides of the anthers from top to bottom, but some species have pores that open at the tips. The Commelinaceae are a well supported monophyletic group according to the analysis of Burns. ""et al."" (2011). The following"
"are the tectum and the foot layer, which is just above the intine. The tectum and foot layer are separated by a region called the columella, which is composed of strengthening rods. The outer wall is constructed with a resistant biopolymer called sporopollenin. Pollen apertures are regions of the pollen wall that may involve exine thinning or a significant reduction in exine thickness. They allow shrinking and swelling of the grain caused by changes in moisture content. Elongated apertures or furrows in the pollen grain are called colpi (singular: colpus) or sulci (singular: sulcus). Apertures that are more circular are"
"the foliage-bearing or vegetative portion, and forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. 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"
"phase produces spores within the sporangium by meiosis. Flowering plants are the dominant plant form on land and they reproduce either sexually or asexually. Often their most distinguishing feature is their reproductive organs, commonly called flowers. The anther produces pollen grains which contain the male gametophytes (sperm). 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"
"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. Stigmas can vary from long and slender to globe-shaped to feathery. The stigma is the receptive tip of the carpel(s), which receives pollen at pollination and on which the pollen grain germinates. The stigma is adapted to catch and trap pollen, either by combining"
"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. It may be divided into chambers (locules) corresponding to the separate carpels. A ""perfect"" flower has both stamens and carpels, and may be described as ""bisexual"" or ""hermaphroditic"". A ""unisexual"" flower is one in which either the stamens or the carpels are missing, vestigial or otherwise non-functional. Each flower is either ""staminate"" (having only functional stamens) and thus ""male"", or ""carpellate"" (or ""pistillate"") (having only functional carpels)"
"Stigma (botany) The stigma (plural: stigmata) is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma, together with the style and ovary comprises the pistil, which in turn is part of the gynoecium or female reproductive organ of a plant. The stigma forms the distal portion of the style or stylodia. The stigma is composed of , the cells which are receptive to pollen. These may be restricted to the apex of the style or, especially in wind pollinated species, cover a wide surface. The stigma receives pollen and it"
"the petals that produce pollen in anthers at their tips. When a pollen grain lands upon the stigma on top of a carpel's style, it germinates to produce a pollen tube that grows down through the tissues of the style into the carpel, where it delivers male gamete nuclei to fertilize an ovule that eventually develops into a seed. In pines and other conifers the sex organs are conifer cones and have male and female forms. The more familiar female cones are typically more durable, containing ovules within them. Male cones are smaller and produce pollen which is transported by"
"other connecting parts. Pollinium A pollinium (plural pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkweeds (Asclepiadoideae). Usage of the term differs: in some orchids two masses of pollen are well attached to one another, but in other orchids there are two halves (with two separate viscidia) each of which is sometimes referred to as a pollinium. Most orchids have waxy pollinia. These are connected to one"
"through a split on the outer side (relative to the center of the flower), this is extrorse dehiscence, and if the pollen is released from the inner side, this is introrse dehiscence. If the pollen is released through a split that is positioned to the side, towards other anthers, rather than towards the inside or outside of the flower, this is latrorse dehiscence. The stomium is the region of the anther where dehiscence occurs. The degeneration of the stomium and septum cells is part of a developmentally timed cell-death program. Expansion of the endothecial layer and subsequent drying are also"
"of the stigma and style. Pollen can also be induced to germinate ""in vitro"" (in a petri dish or test tube). During germination, the tube cell elongates into a pollen tube. In the flower, the pollen tube then grows towards the ovule where it discharges the sperm produced in the pollen grain for fertilization. The germinated pollen grain with its two sperm cells is the mature male microgametophyte of these plants. Since most plants carry both male and female reproductive organs in their flowers, there is a high risk of self-pollination and thus inbreeding. Some plants use the control of"
"Each flower has three to five leathery sepals that mostly end in a stretched tip, making it ""leafy"", but sometimes one and rarely two sepals may be obovate with a rounded tip, which do not fall after flowering. The corolla usually consists of six to nine oblong cyclamen or rarely pink to white petals of 3-6½ × 1½-3 cm. Towards the centre of the flower are many stamens consisting of filaments of ½–1 cm topped with anthers that ripen from the inside out, open with slits and release yellow pollen. The pollen is released in sets of four grains together."
"of five petals, five stamens, and an entire calyx. The stamens usually split and fall off before the stigma becomes receptive to receive pollen. The stamens of the brown, male, sterile flowers degenerate and shrivel before the flower fully opens. In the other type of male sterile flower, the stamens are replaced by petals, and these petals do not fall off. A nectar-containing disc is present on the upper surface of the carpels. Flowers change sex in their development, so the stamens release their pollen before the stigma of the same flower is receptive. The arrangement is centripetal, meaning the"
"of gymnosperms and flowering plants is the germination of a pollen grain after pollination. Like seeds, pollen grains are severely dehydrated before being released to facilitate their dispersal from one plant to another. They consist of a protective coat containing several cells (up to 8 in gymnosperms, 2-3 in flowering plants). One of these cells is a tube cell. Once the pollen grain lands on the stigma of a receptive flower (or a female cone in gymnosperms), it takes up water and germinates. Pollen germination is facilitated by hydration on the stigma, as well as by the structure and physiology"
"Pollinium A pollinium (plural pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as orchids and many species of milkweeds (Asclepiadoideae). Usage of the term differs: in some orchids two masses of pollen are well attached to one another, but in other orchids there are two halves (with two separate viscidia) each of which is sometimes referred to as a pollinium. Most orchids have waxy pollinia. These are connected to one or two elongate"
"ovulate cones, respectively. Gametophytes, as with all heterosporous plants, develop within the spore wall. Pollen grains (microgametophytes) mature from microspores, and ultimately produce sperm cells. Megagametophytes develop from megaspores and are retained within the ovule. Gymnosperms produce multiple archegonia, which produce the female gamete. During pollination, pollen grains are physically transferred between plants from the pollen cone to the ovule. Pollen is usually moved by wind or insects. Whole grains enter each ovule through a microscopic gap in the ovule coat (integument) called the micropyle. The pollen grains mature further inside the ovule and produce sperm cells. Two main modes"
"They are female inflorescences, tightly enveloped by several layers of ear leaves commonly called husks. Certain varieties of maize have been bred to produce many additional developed ears. These are the source of the ""baby corn"" used as a vegetable in Asian cuisine. The apex of the stem ends in the tassel, an inflorescence of male flowers. When the tassel is mature and conditions are suitably warm and dry, anthers on the tassel dehisce and release pollen. Maize pollen is anemophilous (dispersed by wind), and because of its large settling velocity, most pollen falls within a few meters of the"
"middle part (or claws) where the perianth is split lengthwise. These claws are all equally coiled back when the flower has opened, with the outer surface sparsely shaggy haired. The upper part (or limbs), which enclosed the pollen presenter in the bud consists of four lance-shaped lobes of about long, which carry a few stiff hairs. From the perianth emerges a straight or slightly incurved style of about 2 cm (0.8 in) long, tapering in the upper part. The thickened part at the tip of the style called pollen presenter is about 1 mm (0.04 in) long, egg- to hoof-shaped"
"are contained within pollen grains. They develop within the microsporangia, or pollen sacs, of the anthers on the stamens. Each microsporangium contains diploid microspore mother cells, or microsporocytes. Each microsporocyte undergoes meiosis, forming four haploid microspores, each of which can eventually develop into a pollen grain. A microspore undergoes mitosis and cytokinesis in order to produce two separate cells, the generative cell and the tube cell. These two cells in addition to the spore wall make up an immature pollen grain. As the male gametophyte matures, the generative cell passes into the tube cell, and the generative cell undergoes mitosis,"
"from the base of the ovary, or between the ovary lobes and is characteristic of Boraginaceae. Subgynobasic styles characterise ""Allium"". Pollen tubes grow the length of the style to reach the ovules, and in some cases self-incompatibility reactions in the style prevent full growth of the pollen tubes. In some species, including ""Gasteria"" at least, the pollen tube is directed to the micropyle of the ovule by the style. Stigma (botany) The stigma (plural: stigmata) is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma, together with the style and"
"from four sterile stamens (staminodes). Two lateral staminodes form what look like upright petals, often also hooded in shape; two other staminodes are fused together to form a prominent central ""lip"" or labellum. The single fertile stamen has a short filament bearing a cylindrical anther. The connective tissue between the anther's two pollen sacs extends outwards at its base to form spurs. The ovary has three ""cells"" or locules, eventually producing many small arillate seeds. The single functional style extends upwards through a grove in the stamen to appear above its top. The orchid-like flowers with a long floral tube"
"groups—those with cream or yellow flowers and those with some amount of purple in the flowers. Female flowers are even less well known than male flowers. Pollen grains are usually spherical to ellipsoid in shape, sometimes triangular, about 20 to 30 micrometres along their long axis and 20 to 30 µm in diameter. They are typically monosulcate, meridionosulcate or more rarely trichotomosulcate. The sulcus is a furrow which runs along the surface of the pollen grain and is usually the site at which pollination occurs. Monosulcate pollen has a single furrow that runs along the pole of the pollen grain."
"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. 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"
"stems. The stems have opposite leaves. Each flower has five lobes (petals) that are pale pink, lavender, or purple, and is across. The flowers produce pollen on anthers near the end of the corolla tube, and nectar at the bottom of the corolla. Only butterflies, moths, skippers, and very long-tongued bees (the largest bumblebees) have long enough tongues to reach the nectar. Shorter-tongued bees and flower flies visit to feed on or gather pollen. The flowers are self-incompatible. Unless they are cross-pollinated, they will not produce any seed. Butterflies, skippers, and moths are the most effective pollinators. As they insert"
"of roses. Within is a circle of numerous purple filaments topped by yellow anthers. The center of the flower consists of three to nine, initially purple carpels, each of which is connected through a thick style with a reddish stigma on top. The stigmas ripen before the stamens, a situation called protogyny. The three to eight (mostly four to six) carpels develop into dry dehiscent fruits (called follicles) of about 6 cm long, that open with a suture along their lengths, and contain initially carmine colored seeds that turn glossy black when fully ripe. In February the stalks which have"
"The apex of a flowering stem forms a terminal swelling which is called the ""torus"" or receptacle. In those species that have more than one flower on an axis, the collective cluster of flowers is termed an ""inflorescence"". Some inflorescences are composed of many small flowers arranged in a formation that resembles a single flower. The common example of this is most members of the very large composite (Asteraceae) group. A single daisy or sunflower, for example, is not a flower but a flower ""head""—an inflorescence composed of numerous flowers (or florets). An inflorescence may include specialized stems and modified"
"pollen sacs, which contain the microsporocytes. After meiosis, each microspore undergoes mitotic cell division, giving rise to multicellular pollen grains (six nuclei in gymnosperms, three nuclei in flowering plants). Megasporogenesis occurs in megastrobili in conifers (for example a pine cone) and inside the ovule in the flowers of flowering plants. A megasporocyte inside a megasporangium or ovule undergoes meiosis, producing four megaspores. Only one is a functional megaspore whereas the others stay dysfunctional or degenerate. The megaspore undergoes several mitotic divisions to develop into a female gametophyte (for example the seven-cell/eight-nuclei embryo sac in flowering plants). Some fungi and algae"
"a net like appearance consisting of elements (murus, muri) separated from each other by a lumen (plural lumina). The pollen wall protects the sperm while the pollen grain is moving from the anther to the stigma; it protects the vital genetic material from drying out and solar radiation. The pollen grain surface is covered with waxes and proteins, which are held in place by structures called sculpture elements on the surface of the grain. The outer pollen wall, which prevents the pollen grain from shrinking and crushing the genetic material during desiccation, is composed of two layers. These two layers"
"grain. 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"