[The influence of phytochrome on the formation of individual carotenoids in etiolated hordeum seedlings].

Short time red pulses, given 6 times for 5 min within 36 h, induce in etiolated barley seedlings an enhanced synthesis of the main chloroplast carotenoids beta-carotene, violaxanthine, lutein and neoxanthine. The level of antheraxanthine and zeaxanthine decreases by red light treatment. These red light effects are reverted by subsequent short time far-red pulses. The results show that the white light induced change in the accumulation rate of individual carotenoids is initiated and regulated by active phytochrome Pfr. In the case of neoxanthin and zeaxanthin the red light effects cannot be fully reverted by far-red; this points to a very fast phytochrome reaction.