Regulation of propylene-induced ripening and ethylene biosynthesis by oxygen in ‘Hayward’ kiwifruit

Kiwifruit, cv Hayward, were treated with 130 μl/l propylene under 1, 5, 10, 13, 16, and 21% O₂ concentrations in a continuous flow-through system at 20 °C. Control kiwifruit were kept in air (21%O₂). Flesh firmness, soluble solids content, internal ethylene concentration, l-aminocyclopropane-l-carboxylic acid concentration (ACC), malonyl-l-aminocyclopropane-l-carboxylic acid concentration (MACC), and EFE capacity were measured during the experiment. Ethylene biosynthesis and fruit ripening were stimulated when kiwifruit were exposed to a mixture of propylene in 21% O₂. Reduction of oxygen concentration (< 10%) inhibited the effectiveness of propylene on autocatalytic ethylene production possibly through a reduction in ACC concentration in the tissue. Exposure of kiwifruit to low oxygen concentrations (< 5%) delayed propylene-induced fruit ripening.