Abstract:The effects of different light qualities and a special inhibitor of carotenoid biosynthesis on formation of plastid pigments of cotyledons of Pinus sylvestris were studied. The experimental results indicate: 1. The rate of synthesis of carotenoids in far-red light is relatively higher than that of chlorophylls, on the contrary in red light the rate of chlorophyll synthesis is higher. 2. When biosynthesis of carotenoids is inhibited, in white light the rate of total chlorophyll synthesis reduced with similar proportion. Accumulation of chlorophyll, however, is relatively much more than that of carotenoids. The highest molar ratio of chlorophyll/carotenoids is approximately 10.0. This implicates that chlorophyll and carotenoid synthesis proceed with certain independence. 3. After 4h exposure of strong white light of 9 day-old pine seedlings grown with 10-5 mol 1-1 norflurazon in farred light, contents of carotenoids and total, chlorophyll of cotyledons increase. Chlorophyll a biosynthesis promoted by light is higher than photooxidation of the pigment.