Which of the following are examples of tropism?

Tropism refers to the directional growth of a plant in response to external stimuli. This phenomenon involves various types of movements or growth patterns, which can be either positive (toward the stimulus) or negative (away from the stimulus).

Phototropism is the growth of plants toward light, allowing them to maximize photosynthesis. For example, a sunflower turns to face the sun, showcasing this adaptive advantage. Geotropism, on the other hand, relates to a plant's growth in response to gravity; roots typically exhibit positive geotropism (growing downward), while stems show negative geotropism (growing upward).

Both of these responses are essential for a plant’s survival as they help in optimizing light uptake for photosynthesis and ensuring stability through proper root orientation. Hydrotropism (growth toward moisture) and thigmotropism (growth in response to touch) are also valid examples of tropic responses, but the question specifically identifies phototropism and geotropism as key examples, which are quintessential forms of tropism observed in many plant species.