Question

Phototropic curvature is the result of uneven distribution of:

• A. Phytochrome
• B. Gibberellin
• C. Auxin
• D. Cytokinins

Answer 1

The correct option is C

Auxin

The correct option is C:

Explanation of the correct answer:

1. Auxins are plant growth regulators that promote flowering and prevent leaf and fruit drops at early stages.
2. They also promote the abscission of older leaves and fruits.
3. When plants are exposed to the light unilaterally, the auxin gets accumulated towards the shaded side and causes elongation of cells.
4. Thus the uneven distribution of auxin results in phototropism - bending of the plant towards the light source.

Explanation of the incorrect options:

Option A:

1. Phytochromes are photoreceptors in plants.
2. They provide the plant with vital information about light.

Option B:

1. Gibberellins are plant growth regulators that cause an increase in the length of the axis.
2. They also delay senescence.

Option D:

1. Cytokines are plant growth regulators that help to produce new leaves, chloroplasts, lateral shoot growth and adventitious shoot formation.
2. Cytokinins help overcome apical dominance.
3. They promote nutrient mobilization.

Final answer: Phototropic curvature is the result of uneven distribution of auxin.