AP BIOLOGY

Detailed explanation-1: -Positive phototropism is growth towards a light source; negative phototropism is growth away from light.

Detailed explanation-2: -Growth toward or away from a stimulus is known as a tropism. You might have noticed that plants bend toward the light. This is an example of a tropism where light is the stimulus, known as phototropism (Figure below).

Detailed explanation-3: -Phototropism, or the differential cell elongation exhibited by a plant organ in response to directional blue light, provides the plant with a means to optimize photosynthetic light capture in the aerial portion and water and nutrient acquisition in the roots.

Detailed explanation-4: -Plants have evolved a wide variety of responses that allow them to adapt to the variable environmental conditions in which they find themselves growing. One such response is the phototropic response-the bending of a plant organ toward (stems and leaves) or away from (roots) a directional blue light source.

Detailed explanation-5: -Answer: Directional movement and growth of plant in response to light is called as phototropism.