PBIO 004 Lecture Notes - Lecture 15: Phytochrome, Photoperiodism, Daytime
6 Mar 2019
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Photoperiodism: the response plants have to the seasons: photoperiod is the relative length of the night and day. Plants respond to day length according to the age of the plant: broadly speaking, plants responses can be grouped in three ways: Short day plants, which require long nights. Long day plants, which require short nights. Day neutral plants, which do not flower based on photoperiod. Many other environmental indicators are less reliable and vary from year to year (like humidity, temperature, rainfall: day length is stable and varies with latitude and season. Phytochrome is a protein that measures sunrise and sunset, providing the environmental cue to control flower: detects red and far-red light. Can absorb them: provides information to plant about its environment, signals to the plant when it"s time to flower, two forms of phytochrome: red light absorbing (pr) and far-red light absorbing (pfr), which is the active form. Active form is what the plant measures inside its cells.
