Plant sexuality

Flowers, also known as blossoms and blooms, are the reproductive structures of flowering plants. Typically, they are structured in four circular levels around the end of a stalk. These include: sepals, which are modified leaves that support the flower; petals, often designed to attract pollinators; male stamens, where pollen is presented; and female gynoecia, where pollen is received and its movement is facilitated to the egg. When flowers are arranged in a group, they are known collectively as an inflorescence.

clade of seed plants that produce flowers

thumb|350px| Micrograph|Photomicrograph of various seeds

thumb|upright=1.25|Diagram illustrating the process of pollination thumb|upright=1.25|Female carpenter bee with pollen collected from a [[night-blooming cereus]]Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; birds, and bats; water; wind; and even plants themselves. Pollinating animals travel from plant to plant carrying pollen on their bodies in a vital interaction that allows the transfer of genetic ma

thumb|right|250px|Stamens of a Hippeastrum with white filaments and prominent anthers carrying [[pollen]]

thumb|300x300px|In meiosis, the chromosomes duplicate (during [[interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, forming a diploid cell (zygote) with a complete set of paired chromosomes.]]

thumb|Flower of Magnolia × wieseneri|Magnolia × wieseneri showing the many pistils making up the gynoecium in the middle of the flower thumb|Hippeastrum flowers showing stamens, style and stigma thumb|right|Hippeastrum stigmas and style thumb|right|Moss plants with gynoecia, clusters of archegonia at the apex of each shoot.

part of a flower. The pollen-receptive surface of a carpel or group of fused carpels, usually sticky; usually a point or small head at the summit of the style where deposited pollen germinates

thumb|300px|Time course imaging of two maize [[inbreds and their F1 hybrid (middle) exhibiting heterosis.]]

production of new individuals or offspring in plants

Dioecy (; adj. dioecious) is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproduction is biparental reproduction. Dioecy has costs, since only the female part of the population directly produces offspring. It is one method for excluding self-fertilization and promoting allogamy (outcrossing), and thus tends to reduce the expression of recessive deleterious mutations present in a population. Plants have several other methods of preventing self-fe

complex fertilization mechanism of flowering plants

thumb|right|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 a form of pollination in which pollen arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms) of the same plant. The term cross-pollination is used for the opposite case, where pollen from one plant moves to a different plant.

reduced fitness as a result of inbreeding

origin and diversification of plants through geologic time

parts of plant enabling sexual reproduction

300px|thumb|Chasmogamous (a) and cleistogamous (b) flowers of Viola pubescens. Arrows point to structure.

Self-incompatibility (SI) is a general name for any genetic mechanism that prevents self-fertilization in fertile hermaphroditic organisms, and thus encourages outcrossing and allogamy. It is contrasted with separation of sexes among individuals (dioecy), and their various modes of spatial (herkogamy) and temporal (dichogamy) separation.

thumb|Microscopic photo of spores (in red) of Selaginella. The large three spores at the top are megaspores whereas the numerous smaller red spores at the bottom are microspores.

Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity.

thumb|Encephalartos villosus [[microsporophylls with microsporangia]] A microsporangium () is a sporangium that produces microspores that give rise to male gametophytes when they germinate. Microsporangia occur in all vascular plants that have heterosporic life cycles, such as seed plants, spike mosses and the aquatic fern genus Azolla. In gymnosperms and angiosperm anthers, the microsporangia produce microsporocytes, the microspore mother cells, which then produce four microspores through the process of meiosis. Microsporocytes are produced in the microsporangia of gymnosperm cones and the an

study of flower structures