Reduced Sensitivity to Ethylene and Delayed Senescence in a Group of Related Carnation Cultivars

Abstract

Three related carnation cultivars (Ginevra, Epomeo and Chinera) were less sensitive to exogenous ethylene than cv. White Sim. The concentration to give 50% of the maximum response (H_5O) after a 24 h treatment was 0.21 μl 1⁻¹ in cv. White Sim and 0.32, 0.48, and 0.65 μl 1⁻¹, in the cvs. Ginevra, Epomeo, and Chinera, respectively.

When no exogenous ethylene was given the time to petal inrolling was positively correlated with H₅₀. It was about 7 days in cv. White Sim, 12 days in cv. Ginevra, 14 days in cv. Epomeo and 15 days in cv. Chinera. A similar delay was found in the climacteric rise in ethylene production. In cv. Epomeo, moreover, the maximum ethylene production during natural senescence was about one third that in cv. White Sim, and in cv. Chinera about one third that in cv. Epomeo.

When treated with a high dose of ethylene for a short period, the cvs. Chinera and Epomeo responded by producing high amounts of ethylene, indicating that all necessary steps for autocalytic ethylene production are present or can be rapidly induced.

The number of binding sites for ethylene, assessed with an isotope competition technique, was similar in the cvs. Chinera and White Sim. Binding affinity per site was less in cv. Chinera and this may be the basis for its lower sensitivity. It is not known, however, whether assesment of the number of binding sites and their affinity reflects the physiologically active receptor(s). The difference between the cultivars may also be in the signal transduction pathway.