Is Phytochrome a Protein?

Phytochromes consist of a protein, covalently linked to a light-sensing bilin chromophore. The protein part comprises two identical chains (A and B). ... Together, these subunits form the phytochrome region, which regulates physiological changes in plants to changes in red and far red light conditions.

Is phytochrome a hormone?

HORMONE II. In order to detect gravity plant cells must contain amyloplasts (also called "statoliths" in this context). ... The best known photoreceptor in plants is phytochrome, a pigmented protein that exists in two forms: Pr absorbs red light (660nm) and then is converted to Pfr.

What are the two forms of phytochrome?

Phytochrome exists in two interconvertible forms

The forms are named by the color of light that they absorb maximally: Pr is a blue form that absorbs red light (660 nm) and Pfr is a blue-green form that absorbs far-red light (730 nm).