AP BIOLOGY

Detailed explanation-1: -Tropism is specific to the direction of the stimulus. Plants can either display a negative or positive movement in response to a stimulus. It is positive tropism when the movement is towards the direction of stimuli while it is negative tropism when the movement is away from the stimuli.

Detailed explanation-2: -A tropism is directional growth in response to a stimulus. A positive tropism occurs when a plant (or a part of the plant) grows towards the stimulus, and a negative tropism is growth away from the stimulus.

Detailed explanation-3: -Tropism is when a plant moves in response to an external stimulus in the environment. Positive tropism is when a plant moves towards a stimulus. Negative tropism is when a plant moves away from a stimulus.

Detailed explanation-4: -For example, roots will grow down into the ground when gravity is sensed and plants grow towards sunlight so that they can carry out photosynthesis. In both these cases, the plant is reacting to directional stimuli (light and gravity). When a plant reacts to a directional stimuli it is called a tropism.