A small coconut tree sapling was planted in a well lit part of the house while the house was under construction. As the construction work proceeded, the light was blocked from one side. After few years it was observed that the woody stem of the plant has turns and twists in it. Give reason for this unusual [CBSE 2009] appearance of the coconut tree.

Explanation

The plant has received sunlight only from certain directions at different period during the construction work. Hence the auxin has accumulated in the shady part of the plant resulting in cell elongation of that part of the stem. This would have resulted in bending of the plant in the direction of sunlight. Every time the direction of the sun light changes, the plant has bent in that direction as a response to light.
Hence it has an unusual appearance of the trunk.