The tropic movement wherein the tendrils of a pea plant twine around a support.

THIGMOTROPISM (also called haptotropism).

Break the word apart: THIGMO- means touch and -TROPISM means a directional growth movement in response to a stimulus. So thigmotropism is growth in response to TOUCH.

How it works: where the tendril touches the support, the cells on the side AWAY from the contact grow faster than those on the side touching it. That unequal growth makes the tendril curl around the support.

THE TRAP is confusing the tropisms. Learn them as a set, each by its stimulus: PHOTOtropism — light GEOtropism (geotropism) — gravity HYDROtropism — water CHEMOtropism — chemicals THIGMOtropism — touch The prefix always names the stimulus, so the question tells you the answer if you can spot which stimulus it describes.

Do not confuse this with NASTIC movements, which are also responses to a stimulus but are NOT directional — such as the drooping of Mimosa leaves when touched.