Pigment accumulation and photosynthesis in developing rye coleoptiles

Rye seedlings (Secale cereale L.) were grown in darkness or irradiated with white light (WL) of medium intensity (100 mu mol quanta . m(-2). s(-1)). In the coleoptile and primary leaf of irradiated plants synthesis of chlorophylls a and b with average ratios of 2.4 and 2.7, respectively, were measured. The chlorophyll content of the fully green primary leaf was about 10-fold larger than that of the pale green coleoptile. In darkness a large increase in carotenoid content occurred in the primary leaf, but in the coleoptile the level of carotenoids remained very low. In both organs a WL-induced increase in carotenoid synthesis was observed. The level of anthocyanin was likewise enhanced by WL. In the coleoptile and primary leaf of irradiated seedlings light-dependent oxygen evolution was measured. The specific activity of the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase was enhanced after WL treatment. The results indicate that the mature rye coleoptile is a photosynthetically active plant organ.