Which plant hormone is primarily responsible for fruit ripening?

Ethylene is the primary plant hormone responsible for fruit ripening. This gaseous hormone plays a critical role in various stages of the fruit maturation process, including signaling the onset of ripening, which involves changes in color, texture, and flavor. During ripening, ethylene promotes enzymatic activities that break down cell wall components, enhance sugar content, and develop aromatic compounds, all of which transform the fruit from a hard, green state to a soft, sweet, and palatable form.

In commercial and agricultural practices, ethylene is often utilized to control and synchronize ripening in harvested fruit. For example, bananas and tomatoes are typically harvested when still unripe and then exposed to ethylene gas to induce uniform ripening, allowing them to be sold at peak quality.

The other hormones mentioned have different primary functions in plant growth and development. Gibberellins are known for promoting stem elongation and seed germination; auxins are primarily involved in regulating plant growth direction and fruit development; cytokinins play a significant role in cell division and shoot growth. These specialized functions further highlight why ethylene is uniquely suited for initiating and facilitating the ripening process in fruits.