AP BIOLOGY

Detailed explanation-1: -One important light response in plants is phototropism, which involves growth toward-or away from-a light source. Positive phototropism is growth towards a light source; negative phototropism is growth away from light.

Detailed explanation-2: -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-3: -“Photo” means light, and “tropism” means turning. Phototropism is the phenomenon by which the plant bends in the direction of light. Light is required by the plants to stimulate energy production by the process of photosynthesis.

Detailed explanation-4: -Phototropism in plants such as Arabidopsis thaliana is directed by blue light receptors called phototropins. Other photosensitive receptors in plants include phytochromes that sense red light and cryptochromes that sense blue light.

Detailed explanation-5: -Photoperiodism is the response to changes in daylength that enables plants to adapt to seasonal changes in their environment. The best studied example of photoperiodism in plants is flowering, but other responses to daylength include bud dormancy and bulb or tuber initiation.