Plants can be propagated through their two developmental life cycles; the sexual, or the asexual. In the sexual cycle new plants arise after fusion of the parental gametes, and develop from zygotic embryos contained within seeds or fruits. In most cases seedlings will be variable and each one will represent a new combination of genes, brought about during the formation of gametes (meiotic cell division) and their sexual fusion. By contrast, in the vegetative (asexual) cycle the unique characteristics of any individual plant selected for propagation (termed the mother plant, stock plant or ortet) are usually perpetuated because, during normal cell division (mitosis), genes are typically copied exactly at each (mitotic) division. In most cases, each new plant (or ramet) produced by this method may be considered to be an extension of the somatic cell line of one (sexually produced or mutant) individual. A group of such asexually reproduced plants (ramets) is termed a clone. In the natural environment sexual and asexual reproduction have their appropriate selective advantages according to the stage of evolution of different kinds of plants. Plants selected and exploited by man also have different propensities for propagation by seed or by vegetative means.
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