taimedes, bakterites, seentes esinevad punast ja kaugpunast valgust absorbeerivad fotoretseptorid, Phytochromes are a class of photoreceptor present in plants, bacteria and fungi used to detect light. They are sensitive to light in the red and far-red region of the visible spectrum. Linear tetrapyrrole, bound to a protein, acts as the chromophore.