How does a pea plant tendril coil around a support? Name the type of movement involved and explain the mechanism that causes the tendril to wrap.
Generated by claude-sonnet-4-6 · 2026-06-26 01:01 · grounding rag
Model Answer
Type of movement: Tropic movement (growth-dependent movement), specifically thigmotropism.
Mechanism: The tendril of a pea plant is sensitive to touch. When it comes in contact with a support, the part of the tendril touching the object grows less rapidly than the part away from the object. This unequal growth on the two sides causes the tendril to curve and coil around the support, allowing the plant to cling to it.
Source: Chapter 6, Section 6.2.2 – Movement Due to Growth
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Explanation
- Examiners expect you to name the movement type (tropic/thigmotropic) and then explain the differential growth mechanism — slower growth on the contact side vs. faster growth on the free side.
- The key phrase is "unequal/differential growth" — state it clearly.
- Do not confuse this with the sensitive plant's movement, which is growth-independent; tendril coiling is growth-dependent.
- Auxins are involved in causing this differential growth, but the passage focuses on the growth-rate difference — stick to what the source states unless the question specifically asks about auxins.