Question

Charles Darwin and his son, Francis experimented with phototropism of grass seedlings by placing a metal foil blindfold over different parts of the seedling's coleoptile. A simplified version of their results is shown below. Which of the following statements best explains their results ?

• A. The light signal is perceived a few millimetre below the tip, and these cells cause the coleoptile to grow toward the light
• B. Both the seedling root and coleoptile perceive and respond to light in the same manner
• C. A chemical messenger must travel from the base of the coleoptile to the tip
• D. The light signal is perceived at the tip of the coleoptile, but the growth response occurs a few millimetres below the tip

Answer 1

Answer: (D)

Correct answer is (d) The light signal is perceived at the tip of the coleoptile, but the growth response occurs a few millimetres below the tip