AP BIOLOGY

Detailed explanation-1: -The survival of terrestrial plants depends upon the capacity of roots to obtain water and nutrients from the soil. Directed growth of roots in relation to a gradient in moisture is called hydrotropism and begins in the root cap with the sensing of the moisture gradient.

Detailed explanation-2: -Hydrotropism (hydro-“water"; tropism “involuntary orientation by an organism, that involves turning or curving as a positive or negative response to a stimulus") is a plant’s growth response in which the direction of growth is determined by a stimulus or gradient in water concentration.

Detailed explanation-3: -The correct option is D hydrotropism. The movement or the growth of a plant in relation to the stimulus of water is called hydrotropic movement and the equivalent response to the stimulus of water is called hydrotropism.