Oxidative stress, antioxidant capacity and ethylene production during ageing of cut carnation (Dianthus caryophyllus) petals

The objective of this work was to study the role of free radicals in relation to ethylene production during ageing of cut carnation petals. Ethylene production by freshly cut flowers was negligible, but 8 d after cutting ethylene production began to increase and reached a peak by day 9, before beginning to decline again. The efflux of electrolytes (membrane damage index) increased 101% and 2 ,7-dichlorofluorescein oxidation rate (oxidative stress index) increased 53% from day 8 to day 11 after detachment. Ethylene peak was either (a) not affected significantly by the supplementation of exogenous ethylene on the day of cutting, or (b) expanded between days 7-9 after ethylene supplementation on day 6 of cutting, or (c) was inhibited by amino-oxyacetic acid and paraquat treatments. After ethylene supplementation, conductivity and 2,7-dichlorofluorescein oxidation increased significantly as compared to control petals, and the activity of antioxidant enzymes was not affected. However, both w-tocopherol and glutathione content decreased significantly after ethylene supplementation on day 6 after detachment. Amino-oxyacetic acid treatment prevented the increases in conductivity and 2 ,7dichlorofluorescein oxidation, did not alter the activities of antioxidant enzymes and significantly increased the content of a-tocopherol and glutathione as compared to control carnation petals. Paraquat treatment paralleled qualitatively ethylene supplementation after 6 d of cutting. Taken as a whole, the data presented here may be understood as experimental evidence of a close association between ethylene production and oxidative stress in ageing of cut carnations.