Advanced Placement (AP) Biology Practice Exam

What is the term for a growth response in plants that results in curvature toward or away from stimuli?

1. Meristematic growth

2. Photosynthesis

3. Tropism

4. Cell division

The correct answer is: Tropism

The term for a growth response in plants that results in curvature toward or away from stimuli is tropism. This phenomenon occurs when a plant grows in response to environmental factors such as light, gravity, or touch. For example, phototropism is the growth of a plant towards light, while gravitropism is the growth in response to gravity. Tropisms are mediated by differential growth rates in different parts of the plant. When a plant experiences stimuli, such as light coming from one direction, the cells on the side of the plant furthest from the light elongate more than those on the lighted side, causing the plant to bend towards the light source. Similarly, in response to gravity, roots tend to grow downwards due to positive gravitropism, while stems exhibit negative gravitropism and grow upwards. Understanding tropism is essential for grasping how plants adapt to their environment, which influences their survival and reproduction. In contrast, meristematic growth refers to the active cell division occurring in specific areas of plants, photosynthesis is the process of converting light energy into chemical energy, and cell division pertains to the process by which a parent cell divides into two or more daughter cells. None of these focus specifically on the plant's growth response