Question

Why is the colour of a leaf kept in dark frequently turns yellow or pale green? which pigment do you think is more stable?

Answer 1

Since leaves require light to perform photosynthesis, the colour of a leaf kept in the dark changes from a darker to a lighter shade of green. Sometimes, it also turns yellow. The production of the chlorophyll pigment essential for photosynthesis is directly proportional to the amount of light available. In the absence of light, the production of chlorophyll-a molecules stops and they get broken slowly. This changes the colour of the leaf gradually to light green. During this process, the xanthophyll and carotenoid pigments become predominant, causing the leaf to become yellow. These pigments are more stable as light is not essential for their production. They are always present in plants.

Answer 2

Answer:

Chlorophyll fails to absorb the energy in the absence of light; hence it loses stability to give the leaf yellow colouration.

This proves that carotenoids which imparts yellow color is more stable.