Abstract: Seed plants contain five identified photoreceptors and at least one unidentified photoreceptor for blue/UV-A light. Cryptochromes (CRY1 and CRY2) modulate growth while phototrophins (PHOT1 and PHOT2) modulate trophic responses to light. Flavins are the chromophores and absorb in the blue and UV-A range. Considerable information is known about the structure and mode of action of these photoreceptors. The moss Physcomitrella patens contains two identified cryptochromes (CRY1a and CRY1b) which modulate side branch formation and auxin metabolism. Blue light-induced chloroplast movement was mediated by four phototropins. Transduction of the blue/UV-A stimulus does involve calcium signaling in moss cells.