Question

Avena coleoptiles exhibit phototropism when exposed to unilateral light. This is due to -

• A. More rate of growth on the light exposed side
• B. Less rate of growth on the light exposed side
• C. More concentration of auxins on the exposed side.
• D. Less concentration of auxins on the shaded side.

Answer 1

The correct option is B Less rate of growth on the light exposed side

When coleoptiles are exposed to unilateral light, they bend towards light. Auxins facing light undergo destruction due to photooxidation and are transported to the shaded side. Cell elongation is less towards light exposed side and more on shaded side due to more auxins. This unequal growth leads to a bend towards light.