Question

Why is the color of the leaf kept in dark frequently is yellow or pale green?Which pigment do you think is more stable?

Answer 1

Hint: In botany, any green outgrowth from the stem of a vascular plant is normally flattened.As the key photosynthesis sites, leaves provide food for plants, which ultimately nourish and sustain all land animals in turn.

Complete answer:
The main feature of a leaf is photosynthesis to provide food for the plant. The material that gives plants their characteristic green colour, chlorophyll, absorbs light energy.
The colour of a leaf held in the dark shifts from a darker to a lighter shade of green, because leaves need light to perform photosynthesis. Often it turns yellow as well.
 The manufacture of the necessary photosynthesis chlorophyll pigment is directly proportional to the amount of light available. The development of chlorophyll-a molecules ceases in the absence of light, and they slowly break down.

This slowly shifts the colour of the leaf to light green. The xanthophyll and carotenoid pigments become predominant during this process, causing the leaf to become yellow. As light is not necessary for their development, these pigments are more stable. In plants, they are still present.
In the autumn, leaves change colour because the concentrations of pigments change as the leaves prepare to fall from the trees. During the growing season, all leaves slowly lose chlorophyll, and this loss accelerates before the fall of the leaves. This process of chlorophyll loss is very orderly under optimum conditions and helps the plants to resorb most of the nitrogen in the pigment molecule structure.

During ageing, carotenoid pigments are also removed from the plastids, but some of them are preserved in the plastids after extracting the chlorophyll; this produces yellow coloured autumn leaves. In unusual situations, even with winterberry holly, when they fall, a fair amount of chlorophyll is left in the leaves. These leaves have a pale green tint, or maybe a yellow-green combination of chlorophyll and carotenoids.

Note: The most interesting are leaves that turn red, since just before the leaves fall from the trees, this colour is the result of the active synthesis of anthocyanin pigments. Chlorophyll and anthocyanin contain brownish colours. Orange hues are formed by anthocyanins and carotenoids.