A plant chromoprotein involved in the regulation of light-dependent growth processes.

a light-sensitive pigment found within the plant cell. Phytochromes are involved in a number of light-related events, such as seasonal flowering, but are not considered hormones.

A reversible pigment occurring in green plants that changes form in response to exposure to light and dark, permitting plants to measure the length of the dark period.

(fy´ tow krome) [Gr. phyton: plant + chroma: color] • A plant pigment regulating a large number of developmental and other phenomena in plants; can exist in two different forms, one of which is active and the other is not. Different wavelengths of light can drive it from one form to the other.