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Control and Coordination — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10ScienceControl and Coordination1 Mark
MCQ
Plants bend towards a light source as a result of :
  • A
    Inability to synthesise chemical regulators.
  • B
    Increased amount of food synthesised by leaves.
  • C
    Necessity of light for transpiration.
  • ✓
    Unequal auxin distribution in their stems.
✓

Answer

Correct option: D.
Unequal auxin distribution in their stems.
The bending of plant towards light is known as phototropism. It is due to plant hormone auxins. When the growing parts of a phototropic plant detect sunlight, auxins $($synthesized at the shoot tips$)$ help the cells grow longer. When light falls on one side of the plant, the auxins generally diffuse towards the shaded side of the shoot. This stimulates the cells in the shaded area to grow longer than the corresponding cells of the illuminated region. This results in the curvature of the plant stem tip towards the light.

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