Phytochromes in Diatoms: Sensing Far-Red Light in the Deep Blue Sea

In land plants, phytochromes sense red and far-red light and participate in regulation of germination, photomorphogenesis, and circadian rhythms. For aquatic plants, the light spectrum changes with depth, as water attenuates red and far-red wavelengths at increasing depth (Ragni and Ribera d’Alcala, 2004). Nevertheless, many aquatic organisms, including different lineages of algae, have phytochromes, although the functions of these phytochromes remain unclear