HORTICULTURE

Detailed explanation-1: -When phytochrome, a red/far-red-light photoreceptor, absorbs red light during the day, it changes into the physiologically active Pfr (far-red-light-absorbing) form. Upon absorption of far-red light, Pfr is converted back to the inactive Pr (red-light-absorbing) form.

Detailed explanation-2: -Photoperiodism is a biological response to the timing and duration of dark and light periods. Since unfiltered sunlight is rich in red light, but deficient in far-red light, at dawn, all the phytochrome molecules in a leaf convert to the active Pfr form and remain in that form until sunset.

Detailed explanation-3: -Plant Physiology and Development Photoperiodism is the response to changes in daylength that enables plants to adapt to seasonal changes in their environment. The best studied example of photoperiodism in plants is flowering, but other responses to daylength include bud dormancy and bulb or tuber initiation.

Detailed explanation-4: -Phytochromes are a class of photoreceptor in plants, bacteria and fungi used to detect light. They are sensitive to light in the red and far-red region of the visible spectrum and can be classed as either Type I, which are activated by far-red light, or Type II that are activated by red light.