Question

Assertion (A): Phototropism is caused by auxin.

Reason (R): When light is coming frem one side of the plant, auxin diffuses towards the shady side of the shoot.

Options

• Both A and R are true and R is the correct explanation of A.

• Both A and R are true but R is not the correct explanation of A.

• A is true but R is false.

• A is false but R is true.

Answer 1

Both A and R are true and R is the correct explanation of A.

Explanation:

The assertion is true because phototropism, the growth of a plant shoot toward a directional light source, is fundamentally regulated by the hormone auxin. The reason is also true and provides the correct explanation because it outlines the precise mechanical trigger, when unilateral light hits one side of a plant, auxin moves laterally and concentrates on the shaded side. This elevated auxin level accelerates cell elongation exclusively on the darker side, forcing the shoot to bend physically toward the light source.