Photoperiodicity

[foh-tuh-peer-ee-uh-diz-uh m] /ˌfoʊ təˈpɪər i əˌdɪz əm/

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.
/ˌfəʊtəʊˈpɪərɪəˌdɪzəm/
noun
1.
the response of plants and animals by behaviour, growth, etc, to photoperiods
n.

1920, from photoperiod (1920, from photo- + period) + -ism.

photoperiodism pho·to·pe·ri·od·ism (fō’tō-pĭr’ē-ə-dĭz’əm) or pho·to·pe·ri·o·dic·i·ty (-pĭr’ē-ə-dĭs’ĭ-tē)
n.
The response of an organism to changes in its photoperiod, especially as indicated by vital processes.
photoperiodism (fō’tō-pîr’ē-ə-dĭz’əm) also photoperiodicity
(fō’tō-pîr’ē-ə-dĭz’əm)
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.