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2023Q3(v)(a)Chemical Coordination in Plants
Short answerModerate1 mark
3(v)

Study the diagram given below and answer the questions that follow:

Figure for this question

Name the phenomenon shown by the shoot and the root in the diagram.

Topic: Tropic movements in a seedling

Previous-year question practice database

Answer

Exam answer

The SHOOT shows POSITIVE PHOTOTROPISM (growing towards light) and NEGATIVE GEOTROPISM (growing away from gravity). The ROOT shows POSITIVE GEOTROPISM (growing towards gravity) and NEGATIVE PHOTOTROPISM.

Explanation

Use the words POSITIVE and NEGATIVE — they are what earn the mark. Positive means growth TOWARDS the stimulus, negative means AWAY from it.

WHY EACH ORGAN BEHAVES AS IT DOES: the SHOOT must reach LIGHT for photosynthesis, so it grows upward, towards light and against gravity the ROOT must reach WATER and anchor the plant, so it grows downward, with gravity and away from light

Each organ grows in the direction that serves its function, which is why the same seed sends one end up and the other down whichever way you plant it.

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