What effect does gravitropism have on plants?

Gravitropism is a plant response to gravity that significantly influences their growth direction. Specifically, it directs roots to grow downward into the soil, which is crucial for anchoring the plant and accessing water and nutrients from the ground. This downward growth of roots is essential for the plant's stability and overall health.

On the other hand, the other choices address different aspects of plant responses but do not accurately define gravitropism. While stems may grow towards light due to phototropism, this is a separate response and not related to gravity. The enhancement of photosynthesis pertains to the function of leaves rather than growth direction. Likewise, nutrient uptake is more about the plant’s overall interaction with its environment rather than the direct effect of gravitropism. Therefore, the direct impact of gravitropism on root growth downward aptly describes the correct choice.