The growth movements of plant parts in which the direction of the stimulus determines the direction of the response is known as tropic movements or tropism. Plants also have non-directional movements which may not be growth dependent.
Read the source and study the figure, then answer the sub-parts that follow.
Generated by claude-sonnet-4-6 · 2026-06-15 06:50 · grounding stimulus
Model Answer
(I) The movement is Geotropism (Gravitropism). Roots (X) show positive geotropism (grow towards gravity) and shoots (Y) show negative geotropism (grow against gravity).
(II)
(i) Falling of leaves — Abscisic acid (ABA)
(ii) Rapid cell division — Cytokinin
(III) (Since sub-part (a)/(b) options are not provided in the question, a general 2-mark response based on the passage is given below.)
Tropic movements are directional growth movements where the direction of the stimulus determines the direction of the plant's response. For example, phototropism (response to light) and geotropism (response to gravity) are tropic movements. Non-directional movements, such as nastic movements, are independent of the direction of the stimulus and may not be growth-dependent.
Source: Life Processes / Control and Coordination, NCERT Class 10 Science, Chapter 7
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Explanation
- Part (I): The key term is geotropism. Roots grow towards gravity (positive), shoots grow away (negative). Many students confuse positive/negative — remember: positive = towards the stimulus.
- Part (II): ABA (Abscisic Acid) is the "stress hormone" responsible for leaf fall (abscission) and stomatal closure. Cytokinin promotes cell division. These are standard factual points examiners expect.
- Part (III): Since the (a)/(b) options were missing, the answer addresses tropism vs. non-directional movement directly from the passage. In the actual exam, read the option carefully and answer only the chosen one with two clear points.