Ethylene and fruit ripening links named stimuli, coordinating structures and effectors so body systems or plant tissues produce an integrated biological response.
Coverage 2025–2025 · Updated 16 Jul 2026
Ethylene—whose IUPAC name is ethene—drives positive feedback that makes fruit ripening rapid and synchronized.
Ethylene stimulates ripening changes such as softening, colour change and aroma production. Ripening then stimulates further ethylene production, which accelerates ripening in the same fruit and nearby responsive fruits.
Ethylene rises → ripening responses increase → ripening tissue releases more ethylene → response amplifies. Rapid synchronization can make fruits attractive to dispersers at the same time.
A ripe apple can accelerate ripening of nearby climacteric fruit in a closed container because accumulated ethylene reinforces the feedback loop.
Positive feedback amplifies change until ripening is complete or conditions limit it; it does not restore a set point. Fruit type, temperature and oxygen availability affect responsiveness.
This objective is assessed through multiple choice, commonly using Identify.
Identify
Mark schemes reward named structures, correct direction of information flow and explanations that keep the sequence causal.
Treating low oxygen as the only trigger and omitting carbon-dioxide-driven pH change.
Representative question
Which chemical causes positive feedback to ensure rapid ripening of fruit?
Auxin
Cytokinin
Epinephrine
Ethylene
Plant signalling integrates directional growth, phytohormones, and responses to stimuli. Tropisms are directional growth responses in seedlings; experiments compare shoot or root growth under lateral light or gravity stimuli. Shoots show positive phototropism toward lateral light; auxin redistribution causes greater elongation on the shaded side. Phytohormones are plant signalling chemicals controlling growth and development; auxin, cytokinin, and ethylene coordinate responses to stimuli and internal state. PIN auxin efflux carriers actively move auxin between plant cells; asymmetric carrier placement maintains auxin gradients during tropic responses. Auxin activates proton pumping into the apoplast; acidified cell walls loosen, allowing water uptake, elongation, and bending. Auxin generally promotes root formation; cytokinin promotes shoot formation and division; their ratio coordinates root-shoot growth and plant tissue culture outcomes. Ethylene is a gaseous phytohormone that promotes fruit ripening; ripening fruit releases more ethylene, creating positive feedback in nearby fruit.
