PLANTS
PLANT REPRODUCTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Pfr turns into Pr in the light, causing short-day plants to flower
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Pr turns into Pfr in the light, causing long-day plants to flower.
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Pfr turns into Pr in the dark, causing long-day plants to flower.
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Pr turns into Pfr in the dark, causing short-day plants to flower.
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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: -If seeds sense light using the phytochrome system, they will germinate. Plants regulate photoperiodism by measuring the Pfr/Pr ratio at dawn, which then stimulates physiological processes such as flowering, setting winter buds, and vegetative growth.
Detailed explanation-3: -In short-day plants, the active form of phytochrome (Pfr) suppresses flowering. During long periods of darkness (long nights), Pfr is converted to Pr. With Pfr no longer present, flowering is not suppressed, and short-day plants flower.
Detailed explanation-4: -Following synthesis in the cytoplasm, the phytochrome apoprotein binds chromophore and, in the absence of light, this holoprotein folds into a stable, red-light-absorbing conformation, Pr. Absorption of red light by Pr converts the protein to the far-red-absorbing conformation, Pfr.
Detailed explanation-5: -Pfr ceases the repression of Florigen, the flowering signal, or it stimulates expression, and the signal makes the plant flower. Basically, the levels of Pfr tell the plant how long the night is.