AP BIOLOGY

Detailed explanation-1: -Phototropism is one of the many plant tropisms or movements which respond to external stimuli. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism.

Detailed explanation-2: -Growth movement of plants towards the stimulus is known as positive tropism while movement of plant/plant parts away from the stimulus is known as negative tropism. A tropic movement is defined as either positive or negative tropism; not as downward and upward tropism.

Detailed explanation-3: -Positive tropism is when a plant moves towards a stimulus. Negative tropism is when a plant moves away from a stimulus.

Detailed explanation-4: -A tropism is plant movement in response to an external stimulus in the environment. If a plant moves towards a stimulus, then it exhibits positive tropism; if a plant moves away from a stimulus, then it exhibits negative tropism.

Detailed explanation-5: -Tropisms can have a sign: positive if the plant grows toward or in the direction of the stimulus or negative if it moves away from the stimulus.