pho·to·pe·ri·od·ism (f  t-pîr  - -d zm) also pho·to·pe·ri·o·dic·i·ty (-ds-t)n. pl. pho·to·pe·ri·od·isms also pho·to·pe·ri·o·dic·i·ties The response of an organism to changes in its photoperiod, especially as indicated by vital processes. |
photoperiodism [ˌfəʊtəʊˈpɪərɪəˌdɪzəm]
n
(Life Sciences & Allied Applications / Botany) the response of plants and animals by behaviour, growth, etc., to photoperiods
| photoperiodism (ft-pîr--dzm) also photoperiodicity (ft-pîr--ds-t) The response of an organism to changes in its photoperiod, especially as indicated by vital processes. For example, many plants exhibit photoperiodism by flowering only after being exposed to a set amount of daylight, as by requiring either a long or short day to flower. Plant growth, seed germination, and fruiting are also affected by day length. Photoperiodic responses in plants are regulated by special pigments known as phytochromes. In animals, migration, mating, amount of sleep, and other behaviors are also photoperiodic. In many animals, photoperiodism is regulated by the hormone melatonin. |
photoperiodism, photoperiodicity
the effect on the growth and reproduction of plants or animals of varying exposures to light and darkness. Cf. thermoperiodism. — photoperiod, n. — photoperiodic, adj.
See also: Biologythe study of the relative amounts of light and darkness in a 24-hour period required to best effect the growth, reproduction, and flowering of plant species or the growth and reproduction of animals. Also photoperiodicity. Cf. thermoperiodism. — photoperiodic, photoperiodical, adj.
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