AP BIOLOGY

Detailed explanation-1: -In phototropism a plant bends or grows directionally in response to light. Shoots usually move towards the light; roots usually move away from it.

Detailed explanation-2: -A plants response to light has been well documented and studied. It is known to be due to differential elongation of the cells in the plant stem. Stem cells away from the light elongate in response to special auxins (growth hormones) causing the plant stem to bend towards the light.

Detailed explanation-3: -When light falls on one side of the plant, the auxins generally diffuse towards the shaded side of the shoot. This stimulates the cells in the shaded area to grow longer than the corresponding cells of the illuminated region. This results in the curvature of the plant stem tip towards the light.

Detailed explanation-4: -"Even mature plants bend toward the strongest light. They do this by elongating the cells of the stem on the side that is farthest from the light. This type of light-oriented growth is called phototropism, ” explains Prof.

Detailed explanation-5: -The movement of plants due to gravity is called gravitropism. They also do respond to the light. The aerial parts respond positively and grow towards the light whereas the roots respond negatively and grow backward to light. The movement due to lights is known as phototropism.