OMPONENTS OF GENETIC VARIANCE 

Additive genetic variance (VA)

Dominance genetic variance (VD)

Gene interaction variance (VI)

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#Unit 6. System Physiology – Plant

PHY genes encode two types of phytochrome

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#Unit 6. System Physiology – Plant

PHYA is the only gene that encodes a Type I phytochrome. Phytochrome A predominantly perceives far-red light.

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#Unit 6. System Physiology – Plant

Phytochrome B predominantly perceives red light, both phyD and phyE help mediate the shade avoidance response—a response mediated primarily by phyB.

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#Unit 6. System Physiology – Plant

phyB, phyD plays a role in regulating leaf petiole elongation, as well as in flowering time.

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#Unit 6. System Physiology – Plant

Type I phytochrome (phyA) in the light as a result of a combination of factors: inhibition of transcription, mRNA degradation, and proteolysis.

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#Unit 6. System Physiology – Plant

Type II phytochromes, these phytochromes are also present in etiolated plants. The reason is that the expression of their mRNAs is not significantly changed by light, and the encoded phyB through phyE proteins are more stable in the Pfr form than is PfrA.