[The influence of phytochrome on the formation of individual carotenoids in etiolated hordeum seedlings]. / Die Wirkung von Phytochrom auf die Bildung von Einzelcarotinoiden in etiolierten Hordeum-Keimlingen

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.

[Phytochrome system and synthesis of lipoquinones in the plastids of etiolated hordeum seedlings]. / Phytochromsystem und Lipochinonsynthese in den Plastiden etiolierter Hordeum-Keimlinge

Short pulses of red light induce in etiolated barley seedlings an enhanced synthesis of plastidic benzoquinones and vitamin K1, which can be reverted by subsequent irradiation with short pulses of far-red. As compared to the dark there is more formation of plastoquinone-9 than alpha-tocopherol. The enhanced formation of vitamin K1 is coupled with a concomitant decrease in the level of the second naphthoquinone vitamin "K". The data show that active phytochrome Pfr, also in its ground state, induces the light triggered lipoquinone synthesis which is connected to thylakoid formation. The red light induction of enhanced plastoquinone-9 synthesis cannot be fully reverted by subsequent far-red and seems to be a very fast phytochrome response.