In dark-grown or etiolated plants, phytochrome is present in a red light–absorbing form, referred to as Pr. Pr, which to the human eye is blue, is converted by red light to a far-red light–absorbing form called Pfr, which is blue-green.
#Unit 6. System Physiology – Plant#Mechanisms of action of Phytochromes#Part B Pointers
