Why is the colour of a leaf kept in the dark frequently yellow , or pale green ?Which pigment do you think is more stable?
Color of leaf become yellow or pale green in dark due to less or zero production of chlorophyll which is main pigment that imparts green color to the leaves. As plant is away from sunlight so no photosynthesis reaction occur hence plant do not produce chlorophyll. So other pigments like carotene may be expressed in leaves. This carotene is major pigments in plants which give yellow color to the leaves.