| MadSci Network: Botany |
Parthenocarpy in plants is not the same at all as parthenogenesis in animals, which usually results in offspring identical to the single parent. Parthenogenetic offspring develop from a haploid or diploid egg without fertilization. An example of animal parthenogenesis is in aphids where live young are produced with no meiosis and fertilization. Parthenocarpy usually results in no offspring because there are no seeds. An exception is seedless pineapple fruit, which can asexually propagate the plant with its leafy top or crown. The plant process that may be parthenogenesis is usually termed apomixis. In apomixis, seeds are produced without meiosis, just mitosis, so the seedlings are clones of the parent plant. If the apomictic seed arises from an egg cell, then it can also be called parthenogenesis. If the apomictic seed arises from tissue surrounding the embryo sac, then it is still apomixis but not parthenogenesis. The term apomixis can be applied to any asexual method of reproduction but is usually applied to asexual seeds. The term agamospermy is a more specific term for asexual seed formation. Pineapple varieties do not have to be homozygous because they are propagated vegetatively, not by seed. Pineapple requires cross pollination to set seed so would be highly heterozygous in nature. Naturally self-pollinating crops that come true from seed when self-pollinated, such as tomato and bean, would be highly homozygous. However, hybrid tomato and bean seeds could be highly heterozygous. Hybrid seed is often produced commercially by crossing two homozygous parents to form the heterozygous hybrid. Cultivated pineapple fruit is seedless not because it is homozygous or heterozygous but because it is grown under conditions that do not allow for cross pollination. Pineapple cannot successfully self pollinate. Plant tissue culture is explained in the tissue culture websites cited below. Often shoot tips are used in tissue culture but almost any plant part can be used. Leaves, embryos, pith and pollen have been used. In its broadest sense botany is "the scientific study of plants" so would include plant agriculture with its three subsections of horticulture, agronomy and forestry. However, many botany departments in universities often deal more with wild plants than with cultivated plants. Too, botany often includes study of all the kingdoms except the animal kingdom. Therefore, botany departments and botany texts often also deal with algae, bacteria, fungi, and other nonanimals. However, plant agriculture would not be studying about nonplants except as plant pests. This would be the agricultural field of plant pathology. References Parthenogenesis Apomixis: Parthenogenesis & Agamospermy Asexual Reproduction in Plants and Animals Agamospermy Plant tissue culture information exchange Plant tissue culture Plant micropropagation using African violet leaves What is Botany?
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