How does phototropism primarily influence plant growth?

Phototropism primarily influences plant growth by promoting growth towards light sources. This phenomenon occurs because plants possess specific hormones, particularly auxins, which are distributed unevenly in response to light direction. When light shines on one side of a plant, auxins accumulate on the shaded side, causing those cells to elongate more than those on the light-exposed side. This differential growth causes the plant to bend toward the light, optimizing photosynthesis as the leaves increase their exposure to sunlight.

The other options focus on different aspects of plant physiology. For instance, while roots do grow towards moisture, this behavior is primarily a response to hydrotropism, not phototropism. Nutrient absorption from the soil is influenced by various factors such as root structure and soil composition rather than directional growth towards light. Similarly, water intake regulation in stems is more closely related to processes like transpiration and water pressure dynamics rather than phototropic responses.