Which phenomenon describes the plant's growth towards sunlight?

The phenomenon that describes a plant's growth towards sunlight is known as positive phototropism. This process involves plants utilizing light as a directional cue for growth. When a plant is exposed to light, particularly from one side, the hormone auxin is distributed unevenly, causing cells on the shaded side to elongate more than those on the illuminated side. As a result, the plant bends toward the light source to maximize its exposure to sunlight, which is essential for photosynthesis. This growth response enables the plant to optimize its ability to capture light, promote growth, and ensure that it can thrive in its environment.

In contrast, negative phototropism would describe a scenario where a plant grows away from light, which is not applicable in this context. Thigmotropism refers to growth in response to touch or physical contact, commonly observed in climbing plants. Geotropism, on the other hand, is the growth response of a plant in relation to gravity, where roots grow downward (positive geotropism) and stems grow upward (negative geotropism). All these terms describe different types of growth responses, but it is positive phototropism that specifically pertains to growth towards the light source.