The monocots (or monocotyledons) are one of the two major groups of flowering plants (or Angiosperms), the other being the dicots (or dicotyledons). 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. Most monocots reproduce sexually through use of seeds that have a single cotyledon, however a great number of monocots reproduce asexually through clonal propagation. Breeding systems that utilize self-incompatibility are much more common than those that utilize self-compatibility. The majority of monocots are animal pollinated (zoophilous), of which most are pollinator generalists. Monocots have mechanisms to promote or suppress cross-fertilization (allogamy) and self-fertilization (autogamy or geitonogamy). The pollination syndromes of monocots can be quite distinct; they include having flower parts in multiples of three, adaptations to pollination by water (hydrogamy), and pollination by sexual deception in orchids.
Methods of reproduction
Seed production Reproducing through seeds is the most widespread method of reproduction in both monocots and dicots. However, internal seed structure is vastly different between these groups. The cotyledon is the embryonic leaf within a seed; monocots have one whereas dicots have two. The evolution of having one or two cotyledons may have arisen 200-150 Mya when monocots and dicots are thought to have diverged. Furthermore, the cotyledons in dicot seeds contain the endosperm which acts as the seed's food storage, while in monocot the endosperm is separated from the cotyledon. Reproduction through seeds is normally a sexual mode of reproduction, however in some cases individuals can asexually produce fertile seeds without pollination, termed apomixis.
Clonal propagation
Some monocots can reproduce asexually without the need for seeds. Clonal propagation is the production or division of vegetative structures which develop into new individuals that are genetically identical to their progenitor. These vegetative structures can also form enlarged tubers that function as food storage. Monocots constitute the majority of plants with such structures, mainly in the families: Iridaceae, Liliaceae and Amaryllidaceae. There are many different types of clonal propagation, which are classified by the type of tissue propagating.
Rhizomes are root-like stems which usually grow laterally underground or on the ground and sprout new individuals. Most plants that produce rhizomes are monocots (grasses, bamboo, ginger, galangal, turmeric, orchids, irises, lotus); these include the families: Poaceae, Zingiberaceae, Orchidaceae, Iridaceae, and Nelumbonaceae. Stolons (runners) are modified side-branches in which the first internode is extremely elongated and carries a new plantlet, as found in the common houseplant Chlorophytum. They can be found in grasses, irises, and orchids; these include the families: Poaceae, Iridaceae, and Orchidaceae. Bulbs are underground food storage structures made from leaves which cycle through periods of vegetative and reproductive growth. Nearly all bulb producing plants are monocots (onion, lily, tulip, hyacinth, irises); these include the families: Amaryllidaceae, Liliaceae, Asparagaceae, and Iridaceae. Corms are underground swollen stems that act as food storage; they appear similar to bulbs but are not layered with leaves. New corms will bud around the base of the stem. Corms can be found in irises, taro, arrowheads, sedges, and bananas; these include: Iridaceae, Araceae, Alismataceae, Asparagaceae, Colchicaceae, Cyperaceae, and Musaceae. Keikis are clonal individuals that grow from the flowering stems of Orchids.
Breeding systems
Monocots can be classified as perfect (having bisexual flowers), monoecious (having separate male and female flowers on the same plant), dioecious (having flowers of only one sex on an individual) and polygamous (having bisexual flowers with male and/or female flowers on the same plant). Plants that are dioecious have no other option but to mate with different individuals, but in all other cases there is the possibility that an individual's pollen may make contact with its own stigma. For this reason, most plants have genetic mechanisms to prevent fertilization from pollen grains that are too closely related to the stigma (self-incompatibility). The mechanisms of breeding systems occur at the molecular level through a biochemical reaction on the stigma that recognizes genetic differences in pollen grains. Depending on the species, individual plants can self-pollinate, individuals plants can cross-pollinate intraspecifically (between individuals of the same species), or individuals can cross-pollinate interspecifically (between individuals of different species) and hybridize. Orchids are known to have weak barriers to hybridization.
Self-incompatibility
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