LIGHT-STIMULATED SYNTHESIS OF PLASTID QUINONES AND PIGMENTS IN ETIOLATED BARLEY SEEDLINGS

White light promotes the synthesis of carotenoids and plastid quinones. On illumination of etiolated plants light induces the synthesis primarily of those terpenoid lipids that are present in the dark in minor amounts. These are: β-carotene, violaxanthin, neoxanthin and the naphthoquinone vitamin K1. Their synthesis proceeds parallel to the formation of chlorophylls and thylakoids. Concurrently there is a marked decrease in antheraxanthin (plus lutein epoxide). The synthesis of the predominant lipids of the dark-grown plants-lutein, α-tocopherol aqnd total plastoquinone 45 is stimulated by light at a later stage. On illumination a large proportion of plastoquinol 45 is immediately photo-oxidized to plastoquinone 45. The concentration of α-tocoquinone increases, apparently by oxidation of some α-tocopherol. The functional carotenoid and plastid quinone composition of chloroplasts is reached after about 24-h exposure to light. © 1969.