Orchid

Article By:

Sheviak, Charles J. New York State Museum, Albany, New York.

Last reviewed:January 2021

DOI:https://doi.org/10.1036/1097-8542.474500

Any member of the plant family Orchidaceae, having complex, specialized irregular flowers usually with only one or two stamens. The orchid family, Orchidaceae, is among the largest families of plants and is estimated to contain more than 25,000 species. Orchids are monocots; their flowers have inferior ovaries, three sepals, and three petals (Fig. 1). They are distinguished by the differentiation of one petal into a labellum, and the fusion of pistil and stamens into the column. Pollen is usually contained in pollinia, that is, bundles that are removed intact by pollinators, usually insects or sometimes birds. Self-pollination and asexual reproduction without fertilization also occur in orchids. The combination of lip and column structure, flower color, fragrance, and other factors may limit the range of pollinators. Differing pollination mechanisms often provide barriers to cross-pollination between related species. Each flower can produce large quantities of seeds, with numbers in the millions in some tropical species. Seeds are minute, with undifferentiated embryo and no endosperm. Germination and establishment depend on symbiotic mycorrhizae (mutualistic symbioses that are formed by soil-inhabiting fungi and plants) that provide nutrients and water. See also: Asparagales; Flower; Monocotyledons; Mycorrhizae; Orchidales; Pollen; Pollination; Seed; Seed germination

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