Plants respond to stimuli through various mechanisms, notably tropisms and nastic movements. Tropisms are directional growth responses to specific stimuli, such as light (phototropism) or gravity (gravitropism). For instance, plants tend to bend toward light sources to maximize photosynthesis. Nastic movements, on the other hand, are non-directional responses to stimuli, such as the closing of a plant's leaves in response to touch (thigmonasty). These responses are mediated by hormonal changes and can be crucial for survival, enabling plants to adapt to their environment, capture resources, and protect themselves from herbivores.