Question

What causes a green plant exposed to the light, on only one side, to bend towards the source of light as it grows?

(a) Light stimulates plant cells on the lighted side to grow faster.

(b) Auxin accumulates on the shaded side, stimulating greater cell elongation there.

(c) Green plants need light to perform photosynthesis.

(d) Green plants seek light because they are phototropic.

Answer 1

Ans : (b) Auxin accumulates on the shaded side, stimulating greater cell elongation there.

Explanation :

Auxins induce cell elongation. In a differentially illuminated plant, they accumulate in the shaded part, causing elongation of the cells in the shaded part. This unequal elongation on two sides causes the plant to curve or bend towards the light source i.e., phototropic curvature.