Question

common ivy (hedera helix) is a plant that can grow on walls. ivy climbs by means of aerial roots which adhere to the surfaces it grows on. the demonstrates - phototropism hydrotropism thigmotropism gravitropism

Explanation:

To solve this, we analyze each tropism:

• Phototropism: Response to light (not related to surface contact here).
• Hydrotropism: Response to water (not about surface adherence).
• Thigmotropism: Plant growth response to touch/mechanical stimuli. Ivy’s aerial roots adhere to surfaces (touch), so this matches.
• Gravitropism: Response to gravity (not about surface contact).

Answer:

thigmotropism