How Do Plants Reproduce Sexually?
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Identification
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Unlike humans, plant reproduction can happen in a variety of ways using a number of different anatomical structures. The plant kingdom, with all its many species, is made up of two basic categories --angiosperms and gymnosperms. Angiosperms are the flowering plants that produce covered seeds, whereas gymnosperms produce "standalone" seeds. Each category has its own anatomical make-up in terms of male and female reproductive features. Sexual reproduction is possible between plants, or from within an individual plant structure. There are a number of asexual species which reproduce through a type of cloning process, but this method limits the species' ability to differentiate except through mutation. As with humans, plants which reproduce sexually produce offspring that have a new set of biological characteristics, while asexual plants can only reproduce replicas of themselves.
Function
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Plants reproduce by combining their reproductive cells, or gametes. With angiosperms --or flowering plants- gametes combine to produce seeds that remain inside the fruit or flower structures. Gymnosperms produce spores that grow into individual seeds which separate from the plant, to be dispersed in various locations. The seed structure within both groups is considered the male gametophyte, which is a mature grain of pollen. This seed contains a single set of chromosomes. Through the process of pollination, seeds are either carried by insects and birds, or blown by the wind, to land inside the female gametophyte of another plant. The female gametophyte contains the second set of chromosomes. Sexual reproduction in plants occurs when the male and female gametophytes combine.
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Plant Life Cycles
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Plant life cycles are made up of two distinct forms where size, and number of chromosomes differ. Plant cells start with a single set of chromosomes. This is considered the haploid state. When the sex cells, or gametes, combine, this new generation of plants represents the diploid state since these cells now have two sets of chromosomes. Also known as zygotes, the offspring develops into an adult plant through the process of mitosis where their combined chromosomes sets grow through duplication. Since the resulting gamete cells of the offspring plant are all diploid, the organism must undergo a process called meiosis in which the sex cells divide into sets of haploid cells. Once in the haploid state, sex cells are able to reproduce the next generation of offspring.
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