G1/S phase CDKs phosphorylate Cdh1 at the 

G1-S phase transition

TLS Online TPP Program

#Id: 4986

#Unit 6. System Physiology – Plant

Phytochrome is that it enables plants to sense shading by other plants. Plants that increase stem extension in response to shading are said to exhibit a shade avoidance response.

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#Id: 4988

#Unit 6. System Physiology – Plant

As shading increases, the R:FR ratio decreases.

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#Id: 4989

#Unit 6. System Physiology – Plant

The greater proportion of far-red light converts more Pfr to Pr, and the ratio of Pfr to total phytochrome (Pfr/Ptotal) decreases.

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#Id: 4991

#Unit 6. System Physiology – Plant

When stimulated natural radiation was used to vary the far-red content, it was found that for so-called sun plants, the higher the far-red content (i.e., the lower the Pfr:Ptotal ratio), the higher the rate of stem extension.

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#Id: 4992

#Unit 6. System Physiology – Plant

For a “sun plant” or “shade-avoiding plant” there is a clear adaptive value in allocating its resources toward more rapid extension growth when it is shaded by another plant.

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#Id: 4993

#Unit 6. System Physiology – Plant

It can enhance its chances of growing above the canopy and acquiring a greater share of unfiltered, photosynthetically active light.