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 radicalsin relation to ethylene production during ageing of cut carnationpetals. Ethylene production by freshly cut flowers was negligible,but 8 d after cutting ethylene production began to increaseand reached a peak by day 9, before beginning to decline again.The efflux of electrolytes (membrane damage index) increased101% and 2',7'-dichlorofluorescein oxidation rate (oxidativestress index) increased 53% from day 8 to day 11 after detachment.Ethylene peak was either (a) not affected significantly by thesupplementation of exogenous ethylene on the day of cutting,or (b) expanded between days 7–9 after ethylene supplementationon day 6 of cutting, or (c) was inhibited by amino-oxyaceticacid and paraquat treatments. After ethylene supplementation,conductivity and 2',7'-dichlorofluorescein oxidation increasedsignificantly as compared to control petals, and the activityof antioxidant enzymes was not affected. However, both -tocopheroland glutathione content decreased significantly after ethylenesupplementation on day 6 after detachment. Amino-oxyacetic acidtreatment prevented the increases in conductivity and 2',7'-dichlorofluoresceinoxidation, did not alter the activities of antioxidant enzymesand significantly increased the content of -tocopherol and glutathioneas compared to control carnation petals. Paraquat treatmentparalleled qualitatively ethylene supplementation after 6 dof cutting. Taken as a whole, the data presented here may be understoodas experimental evidence of a close association between ethyleneproduction and oxidative stress in ageing of cut carnations. Key words: Carnation petals, oxidative stress, ethylene, antioxidants