Plants exhibit various tropisms in response to external stimuli. Phototropism is the growth of plants in response to light, with shoots growing towards light and roots away from it. Geotropism is the growth of plants in response to gravity, with roots growing downward and shoots upward. Hydrotropism is the growth of plants in response to water, with roots growing towards water and shoots away from it. Thigmotropism is the response of climbing plants to touch, allowing them to grow upwards for sunlight. Nastic movements do not depend on the direction of stimuli, with plants responding to external stimuli from any direction.