A grapevine coiling around a fence post is an example of WHAT?

A grapevine coiling around a fence post is an example of thigmotropism, which is a plant's growth response to touch or physical contact with an object. This phenomenon allows the plant to support itself and grow upward, maximizing its exposure to sunlight. The coiling behavior is facilitated by specialized structures called tendrils, which help the vine cling to surfaces.