AP BIOLOGY

Detailed explanation-1: -Tropisms are growth toward or away from a stimulus. Types of tropisms include gravitropism (gravity), phototropism (light), and thigmotropism (touch). Plant roots always grow downward because specialized cells in root caps detect and respond to gravity. This is an example of a tropism.

Detailed explanation-2: -Some common plant stimuli include light, gravity, water, movement of the sun, and touch. The naming of the tropism is associated with the stimulus. For example, the movement of plant roots towards water is called hydrotropism.

Detailed explanation-3: -Plants respond to their environment. They grow toward light. Plant leaves bud and seeds germinate when the temperature is right. Their roots and stems grow in certain directions in response to the pull of gravity.

Detailed explanation-4: -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.

Detailed explanation-5: -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.