Science — CBSE Class 10 board question

(i) Tropic Movements:
Tropic movements are directional movements of a plant part in response to an external stimulus, where the direction of movement is determined by the direction of the stimulus.

• Hormone that inhibits growth: Abscisic acid (ABA)
• Hormone that promotes cell division: Cytokinin

(ii) Movement of Tendril in Pea Plant:
When a tendril touches a support, the cells on the side of the tendril away from the support grow faster (more auxin accumulates there), while the cells on the touching side grow slower. This unequal growth causes the tendril to curl around the support, enabling the plant to climb.

This movement is an example of thigmotropism (touch tropism). The hormone responsible is Auxin, which causes differential growth by promoting cell elongation on the side away from the stimulus.

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• Tropic movements are always directional — caused by unilateral (one-sided) stimuli. Don't confuse with nastic movements (non-directional).
• For the hormone part: ABA (abscisic acid) inhibits growth; cytokinin promotes cell division. Some students wrongly write gibberellin — that promotes stem elongation, not primarily cell division.
• For the tendril answer, examiners want: differential growth → auxin redistribution → curling. The word thigmotropism must appear.
• Always name the hormone explicitly; vague answers lose marks.