Which plant hormone is responsible for fruit ripening?

The plant hormone responsible for fruit ripening is ethylene. Unlike most plant hormones, ethylene is a simple gaseous molecule, and plants produce it in tiny amounts as fruits mature.

Ethylene is especially important in climacteric fruits, such as bananas, apples, pears, tomatoes, and avocados. In these fruits, rising ethylene triggers changes including softening, color development, aroma production, and the conversion of stored starches into sugars. A ripe fruit can release more ethylene, helping coordinate ripening nearby. This is why a ripe banana may accelerate ripening in other fruit kept in the same container.

Not every fruit depends on ethylene in the same way. Non-climacteric fruits, including grapes and strawberries, generally do not show the same dramatic ethylene-driven ripening surge, although ethylene can still affect some of their processes. Auxin, abscisic acid, and other signals also influence fruit development, but ethylene is the classic quiz answer for ripening.

Scientists identified ethylene’s role through observations of illuminating gas and kerosene lamps. By 1924, experiments by Frank E. Denny showed that ethylene could make green citrus fruit change color more quickly.