In 1948, spectrograph tests indicated that a single pigment was responsible for the photoperiodis. In 1952, tests revealed that
germination was stopped when a plant was exposed to farred light and restarted when exposed to red light. In 1959, the team
performed conclusive tests on turnip seeds and named the pigment phytochrome.
Photoperiod is the duration of sunlight received by any place.It affects the natural vegetation of any
place. The photoperiod is different at different places because of the variations in latitude, altitude, season
and duration of the day