In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population.
Plant reproductive morphology is the study of the physical form and structure of those parts of plants directly or indirectly concerned with sexual reproduction.
Self-incompatibility (SI) is a general name for several genetic mechanisms that prevent self-fertilization in sexually reproducing organisms, and thus encourage outcrossing and allogamy. It is contrasted with separation of sexes among individuals (dioecy), and their various modes of spatial (herkogamy) and temporally (dichogamy) separation.
Heterostyly is a unique form of polymorphism and herkogamy in flowers. In a heterostylous species, two or three morphological types of flowers, termed "morphs", exist in the population. On each individual plant, all flowers share the same morph. The flower morphs differ in the lengths of the pistil and stamens, and these traits are not continuous. The morph phenotype is genetically linked to genes responsible for a unique system of self-incompatibility, termed heteromorphic self-incompatibility, that is, the pollen from a flower on one morph cannot fertilize another flower of the same morph.
Dioecy is a characteristic of certain species that have distinct unisexual individuals, each producing either male or female gametes, either directly or indirectly. Dioecious reproduction is biparental reproduction. Dioecy has costs, since only about half 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-fertilization including, for example, dichogamy, herkogamy, and self-incompatibility.
A supergene is a chromosomal region encompassing multiple neighboring genes that are inherited together because of close genetic linkage, i.e. much less recombination than would normally be expected. This mode of inheritance can be due to genomic rearrangements between supergene variants.
Sequential hermaphroditism is one of the two types of hermaphroditism, the other type being simultaneous hermaphroditism. It occurs when the organism's sex changes at some point in its life. In particular, a sequential hermaphrodite produces eggs and sperm at different stages in life. Sequential hermaphroditism occurs in many fish, gastropods, and plants. Species that can undergo these changes from one sex to another do so as a normal event within their reproductive cycle that is usually cued by either social structure or the achievement of a certain age or size. In some species of fish, sequential hermaphroditism is much more common than simultaneous hermaphroditism.
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants. Flowers produce gametophytes, which in flowering plants consist of a few haploid cells which produce gametes. The "male" gametophyte, which produces non-motile sperm, is enclosed within pollen grains; the "female" gametophyte is contained within the ovule. When pollen from the anther of a flower is deposited on the stigma, this is called pollination. Some flowers may self-pollinate, producing seed using pollen from the same flower or a different flower of the same plant, but others have mechanisms to prevent self-pollination and rely on cross-pollination, when pollen is transferred from the anther of one flower to the stigma of another flower on a different individual of the same species.
Arcytophyllum is a genus of flowering plants in the family Rubiaceae. The genus contains 18 species, distributed from New Mexico to Bolivia.
Leavenworthia is a genus of flowering plants in the family Brassicaceae. It includes about eight species native to the southern and southeastern United States. They are known generally as gladecresses.
Hypericum aegypticum is a species of flowering plant of the St. John's wort family (Hypericaceae) which is native to the Eastern Mediterranean. It was described by Carl Linnaeus in the second volume of his Species Plantarum in 1753, who named it after Egypt despite it not being distributed there. The plant is commonly known as shrubby St. John's wort or Egyptian St. John's wort in English. Like other members of section Adenotrias, it is found among limestone rocks in coastal areas. While it has been evaluated as threatened on the island of Malta, the species has no legal protections.
Spencer Charles Hilton Barrett is a Canadian evolutionary biologist, formerly a Canada Research Chair at University of Toronto and, in 2010, was named Extraordinary Professor at University of Stellenbosch.
The monocots are one of the two major groups of flowering plants, the other being the dicots. In order to reproduce they utilize various strategies such as employing forms of asexual reproduction, restricting which individuals they are sexually compatible with, or influencing how they are pollinated. Nearly all reproductive strategies that evolved in the dicots have independently evolved in monocots as well. Despite these similarities and their close relatedness, monocots and dicots have distinct traits in their reproductive biologies.
Reproductive assurance occurs as plants have mechanisms to assure full seed set through selfing when outcross pollen is limiting. It is assumed that self-pollination is beneficial, in spite of potential fitness costs, when there is insufficient pollinator services or outcross pollen from other individuals to accomplish full seed set.. This phenomenon has been observed since the 19th century, when Darwin observed that self-pollination was common in some plants. Constant pollen limitation may cause the evolution of automatic selfing, also known as autogamy. This occurs in plants such as weeds, and is a form of reproductive assurance. As plants pursue reproductive assurance through self-fertilization, there is an increase in homozygosity, and inbreeding depression, due to genetic load, which results in reduced fitness of selfed offspring. Solely outcrossing plants may not be successful colonizers of new regions due to lack of other plants to outcross with, so colonizing species are expected to have mechanisms of reproductive assurance - an idea first proposed by Herbert Baker and referred to as Baker's Law. Baker’s Law predicts that reproductive assurance should be common in weedy plants that persist by colonizing new sites. As plants evolve towards increase self-fertilization, energy is redirected to seed production rather than characteristics that increased outcrossing, such as floral attractants, which is a condition known as the selfing syndrome.
Floral color change occurs in flowers in a wide range of angiosperm taxa that undergo a color change associated with their age, or after successful pollination.
Distyly is a type of heterostyly in which a plant demonstrates reciprocal herkogamy. This breeding system is characterized by two separate flower morphs, where individual plants produce flowers that either have long styles and short stamens, or that have short styles and long stamens. However, distyly can refer to any plant that shows some degree of self-incompatibility and has two morphs if at least one of the following characteristics is true; there is a difference in style length, filament length, pollen size or shape, or the surface of the stigma. Specifically these plants exhibit intra-morph self-incompatibility, flowers of the same style morph are incompatible. Distylous species that do not exhibit true self-incompatibility generally show a bias towards inter-morph crosses - meaning they exhibit higher success rates when reproducing with an individual of the opposite morph.
Cryptic self-incompatibility (CSI) is the botanical expression that's used to describe a weakened self-incompatibility (SI) system. CSI is one expression of a mixed mating system in flowering plants. Both SI and CSI are traits that increase the frequency of fertilization of ovules by outcross pollen, as opposed to self-pollen.
June Nasrallah is Barbara McClintock Professor in the Plant Biology Section of the School of Integrative Plant Science at Cornell University. Her research focuses on plant reproductive biology and the cell-cell interactions that underlie self-incompatibility in plants belonging to the mustard (Brassicaceae) family. She was elected to the US National Academy of Sciences in 2003 for this work and her contributions generally to our understanding of receptor-based signalling in plants.
Pollinator-mediated selection is an evolutionary process occurring in flowering plants, in which the foraging behavior of pollinators differentially selects for certain floral traits. Flowering plant are a diverse group of plants that produce seeds. Their seeds differ from those of gymnosperms in that they are enclosed within a fruit. These plants display a wide range of diversity when it comes to the phenotypic characteristics of their flowers, which attracts a variety of pollinators that participate in biotic interactions with the plant. Since many plants rely on pollen vectors, their interactions with them influence floral traits and also favor efficiency since many vectors are searching for floral rewards like pollen and nectar. Examples of pollinator-mediated selected traits could be those involving the size, shape, color and odor of flowers, corolla tube length and width, size of inflorescence, floral rewards and amount, nectar guides, and phenology. Since these types of traits are likely to be involved in attracting pollinators, they may very well be the result of selection by the pollinators themselves.
