Shoots of plant show upward movement and it can be designated to be
- A.Negatively phototropic
- B.Positively chemotropic
- C.Positively hydrotropic
- D.Negatively geotropic
Correct answer
Explanation
The correct answer is D, Negatively geotropic. A shoot grows upward, away from the pull of gravity, so it is negatively geotropic. A tropism is a directional growth movement of a plant part in response to a stimulus: towards the stimulus is positive, away from it is negative. Roots grow downward towards gravity and are positively geotropic, while shoots grow up against it. Shoots also bend towards light, so they are positively phototropic. These bending movements are controlled by the plant hormone auxin, which collects on one side of the shoot and makes that side grow faster. Option A is wrong because shoots grow towards light, which is positive, not negative, phototropism. Option B is wrong because chemotropism is growth in response to chemicals, seen in the pollen tube growing towards the ovule, not in the upward growth of shoots. Option C is wrong because positive hydrotropism, growth towards water, is shown by roots. Exam tip: shoots are positively phototropic and negatively geotropic; roots are the reverse.
Practice Questions
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