photoperiodism

[ foh-tuh-peer-ee-uh-diz-uhm ]

noun

, Biology.

1. the response, as affecting growth or reproduction, of an organism to the length of exposure to light in a 24-hour period.

photoperiodism

/ ˌfəʊtəʊˈpɪərɪəˌdɪzəm /

noun

1. the response of plants and animals by behaviour, growth, etc, to photoperiods

photoperiodism

/ fō′tō-pîr′ē-ə-dĭz′əm /

1. 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 .

Word History and Origins

Origin of photoperiodism¹

First recorded in 1915–20; photoperiod + -ism