Amniote cell specification (germ layer identity)is established before gastrulation starts, but the specification of cell type is controlled by inductive influences during and after migration through the primitive streak.

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#Id: 4577

#Unit 6. System Physiology – Plant

Light wavelengths detected by plant light receptors.

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#Id: 4578

#Unit 6. System Physiology – Plant

Phytochrome Can Interconvert between Pr and Pfr Forms

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#Id: 4579

#Unit 6. System Physiology – Plant

Effects of red light (650–680 nm) on morphogenesis could be reversed by a subsequent irradiation with light of longer wavelengths (710–740 nm), called far-red light. This phenomenon was first demonstrated in germinating seeds.

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#Id: 4580

#Unit 6. System Physiology – Plant

In dark-grown or etiolated plants, phytochrome is present in a red light–absorbing form, referred to as Pr because it is synthesized in this form.

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#Id: 4581

#Unit 6. System Physiology – Plant

Pr, which to the human eye is blue, is converted by red light to a far-red light–absorbing form called Pfr, which is bluegreen.

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#Id: 4582

#Unit 6. System Physiology – Plant

Pfr, in turn, can be converted back to Pr by far-red light. Known as photoreversibility, this conversion/reconversion property is the most distinctive property of phytochrome.