What term describes the directional growth response in plant shoots toward lateral light sources?

The correct term that describes the directional growth response in plant shoots toward lateral light sources is positive phototropism. In this process, plants possess photoreceptors that detect light and facilitate the uneven distribution of auxins, which are plant hormones that promote cell elongation. When light is more intense on one side of a shoot, auxins accumulate on the shaded side, causing those cells to elongate more than those on the light-exposed side. This results in the shoot bending towards the light source, which maximizes light exposure for photosynthesis.

In this context, the other terms refer to different growth responses: negative phototropism involves growth away from light, which does not apply here. Gravitropism is the plant's growth response to gravity, affecting root and shoot orientation, and hydrotropism refers to growth in response to moisture gradients in the soil. These concepts differentiate them from phototropism, which specifically pertains to light-induced growth patterns.