tropismsgrowth

Tropisms are directional growth responses of plants to external stimuli. These stimuli can include light, gravity, touch, water, and chemicals. The plant's growth is directed either towards or away from the stimulus.

Phototropism is the response to light. Shoots typically exhibit positive phototropism, growing towards a light source, which is crucial for photosynthesis. Roots, on the other hand, usually display negative phototropism, growing away from light, as they are typically found underground.

Gravitropism, also known as geotropism, is the response to gravity. Shoots generally grow against gravity (negative gravitropism), while roots grow with gravity (positive gravitropism). This ensures that shoots emerge from the soil and roots anchor the plant and absorb water.

Thigmotropism is the growth response to touch. Tendrils of climbing plants, for instance, coil around a support structure when they come into contact with it, allowing the plant to ascend.

Hydrotropism is the growth response to water. Roots will grow towards a source of water, even if it means growing against the direction of gravity, to ensure the plant's hydration.

Chemotropism is the growth response to chemical stimuli. For example, pollen tubes grow towards ovules in response to chemical signals. Tropisms are mediated by plant hormones, primarily auxins, which accumulate on one side of a plant organ and promote or inhibit cell elongation, leading to bending.