BIOLOGY
HORMONES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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absorb green light followed by red light
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revert back and forth between two forms of phytochromes that differ in structure
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absorb far-red light followed by red light
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respond to red light only
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Detailed explanation-1: -The phytochrome system acts as a biological light switch. It monitors the level, intensity, duration, and color of environmental light. The effect of red light is reversible by immediately shining far-red light on the sample, which converts the chromoprotein to the inactive Pr form.
Detailed explanation-2: -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.
Detailed explanation-3: -Plants also use phytochrome to move towards light and away from shade – this is called the Shade avoidance response. Since more blue and red light is absorbed by the upper canopy compared to green and far-red, this distributes more green and far-red light to lower in the canopy.
Detailed explanation-4: -Since, in the early days, all phytochrome molecules in a leaf are rich in red light, but in far-root light, they become active Pfr and remain in this state until sunset. Since Pfr returns to Pr during the darkness, no Pfr will remain at the rising of the sun if the night is long (winter) (summer).