AP BIOLOGY

Detailed explanation-1: -Thigmotropism describes plant growth in response to touch or contact with a solid object. Positive thigmostropism is demonstrated by climbing plants or vines, which have specialized structures called tendrils. A tendril is a thread-like appendage used for twinning around solid structures.

Detailed explanation-2: -Examples of positive thigmotropism are the growth of ivy on walls upon contact to walls and the coiling of tendrils or twiners upon contact to objects for support. An example of negative thigmotropism is the growth of roots underneath the soil.

Detailed explanation-3: -Thigmotropism is the directional response of a plant organ to touch or physical contact with a solid object. This directional response is generally caused by the induction of some pattern of differential growth. This phenomenon is clearly illustrated by the climbing tendrils of some plants, such as the sweet pea.