What causes uneven growth on one side of a plant?

Uneven growth on one side of a plant is primarily driven by the distribution and action of auxins, which are plant hormones that regulate growth. When a plant is exposed to directional light, auxins will accumulate on the shaded side of the plant. This accumulation stimulates cell elongation more on the shaded side than on the side receiving direct sunlight. As a result, the shaded side grows longer, causing the plant to bend toward the light source. This phenomenon is known as phototropism.

While water absorption, light exposure, and soil nutrients can influence plant growth overall, they typically do not directly cause the localized uneven growth seen when a plant bends toward light. Water absorption is essential for cell growth and turgor pressure but doesn't lead to differential growth on its own. Similarly, although light exposure is a factor in overall growth, its direct role in uneven growth is primarily mediated through the action of auxins responding to light conditions. Soil nutrients impact overall health and vigor but are not directly responsible for the uneven distribution in growth.