Question

Phototropic curvature is the result of uneven distribution of ______.

Options

• Gibberellins

• Phytochrome

• Cytokinins

• Auxin

Answer 1

Phototropic curvature is the result of uneven distribution of auxin.

Explanation:

When a plant shoot is exposed to a one-sided (unilateral) light source, the plant hormone auxin migrates laterally and accumulates on the darker, shaded side. Higher concentrations of auxin actively stimulate cell elongation and wall loosening in shoots. Because the cells on the shaded side grow and expand significantly faster than the cells on the light-exposed side, this unequal growth rate forces the stem to bend directly toward the light.