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Concept 39.3: Responses to light are critical for plant success - Coggle…
Concept 39.3: Responses to light are critical for plant success
Classes of light receptors
Regulating plants' photomorphogenesis
Blue-light photoreceptors
Initiates a variety of responses in plants
Phototropism
The light-induced opening of stomata
The light-induced slowing of hypocotyl
elongation
Absorb blue light
Phototropin is a protein kinase involved in mediating blue-light-mediated stomatal opening, chloroplast movements in response tolight, and phototropic curvatures
Cryptochromes, molecular relatives of DNA repair enzymes, are involved in the blue-light-induced inhibition of stem elongation that occurs
Phytochrome Photoreceptors
Phytochromes
Act like molecular “on-off” switches that regulate
shade avoidance and germination of many seed types
Red light
turns phytochrome “on
Far-red light turns it “off "
Provides information about the day length (photoperiod) and hence the time of year
Absorb mostly red light
Biological Clocks and Circadian Rhythms
Photoperiodism
Regulates the time of flowering in many species
Short-day plants require a night longer than a critical length to flower.
Long-day plants need a night length shorter than a critical period to flower.
Many daily rhythms in plant behavior are controlled by an internal circadian clock.
Free-running circadian rhythms are approximately 24 hours long
Are entrained to exactly 24 hours by dawn and dusk effects on phytochrome form