What term describes a plant's response to a stimulus?

The term that describes a plant's response to a stimulus is "tropism." This is a vital concept in plant biology, referring to the directional growth or movement of a plant in response to environmental stimuli. For instance, phototropism is when a plant grows towards light, while gravitropism refers to growth in response to gravitational pull. These responses are crucial for the plant's survival, enabling it to optimize its exposure to sunlight and roots to stabilize and absorb nutrients from the soil.

Reproduction, the second option, pertains to the biological processes by which plants produce offspring, rather than their responses to environmental factors. Photoactivation relates to the activation of biological responses through light but does not specifically indicate the directional growth pattern. Hydrolysis refers to a chemical process involving the breakdown of compounds due to the reaction with water, rather than describing a growth or movement response in plants. Thus, tropism is the most appropriate term for a plant's directional response to stimuli.