Why is the colour of a leaf kept in the dark frequently yellow, or pale green? Which pigment do you think is more stable?
In the absence of light chlorophyll is unable to absorb the energy and becomes unstable and yellow coloration is observed. The yellow color seen is due to the presence of carotenoid which is more stable. For the production of carotenoid light is not necessary whereas for chlorophyll light is necessary. Chlorophyll, carotenoid are plant photosynthetic pigments. The solar energy required for photosynthesis is captured by them. Chlorophyll is present in all photosynthetic organisms. There are several types of chlorophyll molecules, chla, chlb chlc and chld. These pigments are lipid soluble. The other two accessory pigments are carotenoids and phycobilins. Carotenoids are long-chain hydrocarbon and act as accessory light-harvesting pigments. Phycobilins are non-cyclic, linear tetrapyrrole structures, which are structurally similar to bile pigment bilirubin. Carotenoid is more stable than chlorophyll. It can be produced even in the dark. Final Answer The production of chlorophyll for photosynthesis to carry out. Production of chlorophyll a molecule ceases when light is absent and chlorophyll molecule degenerate slowly and the color of leaf changes gradually. During this entire process carotenoid and xanthophylls predominates in leaves. Carotenoid and xanthophylls are stable in dark.
