PLANTS
PLANT REPRODUCTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Pfr is stimulatory in long day plants
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Pfr levels are in short day plants
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The period of darkness required to stimulate flowering must be uninterrupted
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Far-red light causes a slow reversion to inactive Pr
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Detailed explanation-1: -The Phytochrome System and Growth The exposure to red light converts phytochrome in the shaded leaves to the Pr (inactive) form, which slows growth . The leaves in full sunlight are exposed to red light and have activated Pfr, which induces growth toward sunlit areas.
Detailed explanation-2: -The phytochrome photoreceptors are proteins that bind a tetrapyrrole chromophore, allowing them to absorb light. These phytochromes exist in two photo-interconvertible forms: an inactive, red-absorbing “Pr” form and an active, far-red–absorbing “Pfr” form.
Detailed explanation-3: -Absorption of red light by Pr converts the protein to the far-red-absorbing conformation, Pfr. Absorption of far-red light by Pfr converts the conformation back to Pr (Figure 1).
Detailed explanation-4: -The active form of phytochrome (P fr) is broken down into the inactive form when it absorbs far red light ( 725 nm) Additionally, the active form will gradually revert to the inactive form in the absence of light (darkness reversion)