ACCUMULATION OF PIGMENTS DURING THE GREENING OF ETIOLATED SEEDLINGS OF HORDEUM-VULGARE L

The pigment changes that occur during transformation of etioplasts to fully developed chloroplasts have been studied in seedlings of barley (Hordeum vulgare L.) by greening with white light of low (15-25-mu-mol m-2 s-1) and medium (150 mu-mol m-2 s-1) intensity. At least 24 h longer was required in the low light regime for the same concentration of pigment to be accumulated in the seedlings. The increase in pigment content was mainly due to the synthesis of chlorophylls a and b. Of the carotenoids present, the increases in the levels of neoxanthin and, especially, beta-carotene were much greater than those observed for the other carotenoids. Levels of lutein also increased but this change was small by comparison to those observed for neoxanthin and beta-carotene. In the long-term the concentration of violaxanthin remained unaltered although significant transient changes were recorded. The levels of antheraxanthin and zeaxanthin were markedly reduced during greening. The rate of pigment synthesis decreased with increasing cell age, i.e. from the base to the tip of the primary leaf. Overall, carotenoid levels increased by approximately 100% at the base of the seedling but hardly at all at the tip.