Dioecy (Greek: "two households"; adjective form: dioecious) is characterised by a species having distinct male and female organisms. This is opposed to hermaphroditic species, or more correctly, monoecious species, in which on one individual both male and female reproductive organs are present. Dioecious reproduction is biparental reproduction. The term dioecy is generally used for plants; gonochory is a synonym of dioecy that is generally used in reference to animals.
The situation is somewhat more complicated for organisms which have an alternation of generations, such as land plants, since the sporophyte generation produces spores rather than gametes and hence, strictly speaking, does not have either male or female reproductive organs. The sporophyte generation is called dioecious when each sporophyte has only one kind of spore-producing organ whose spores ultimately give rise to either all male or all female gametes. Slightly different terms, "dioicous" and "monoicous", may be used for the gametophyte generation, although "dioecious" and "monoecious" are also used.
The majority of plant species are not entirely dioecious. They may instead have only bisexual flowers, or they possess some mixture of male, female, and bisexual flowers on at least some individual plants. Still, a significant number of plant species (6% estimated by Renner and Ricklefs) are fully dioecious.
- K. S. Bawa (1980). "Evolution of Dioecy in Flowering Plants". Annual Review of Ecology and Systematics 11: 15–39.
- Stearn, W.T. (1992). Botanical Latin: History, grammar, syntax, terminology and vocabulary, Fourth edition. David and Charles.
- David, J.R. (2001). "Evolution and development: some insights from evolutionary theory". Anais da Academia Brasileira de Ciências 73 (3): 385–395.
- Renner, S. S., and R. E. Ricklefs (1995). "Dioecy and its correlates in the flowering plants". American Journal of Botany 82: 596–606.
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