Lipid peroxidation and antioxidants in apples exposed to sunburn injury

COLAVITA G.M; ORIOLI G; VENTURINO A

Villa Carlos Paz

Congreso; XXXVIII Reunión Anual de la SAIB; 2002

SAIB

Sunburn damage in apple fruits is a problem of concern at regions having high temperatures and intense sunlight, which may lead to membrane damage and brownish through reactive oxygen species generation. In this work we examined the changes in lipid peroxidation, Acid-Soluble Thiols (AST) and Ascorbate (AA) in the adaptive development of sun-exposed apples (cultivar "Braeburn") vs. shaded controls. Fruit development was accompa­nied by an increase in lipid peroxides at maturity. Continuous solar stress induced a higher membrane peroxidation compared to con­trols (3.0 vs. 1.8 µmoles TBARS /g FW at harvest, 1'<0.00 1). Lipid peroxidation was positively correlated to sunburn damage level in exposed fruits (p<0.001). When protected fruits were exposed to sun, a sharp increase of lipid peroxides preceded necrosis. AST levels in sun-exposed fruits were 64% higher than controls at har­vesting (p<0.001), and increased 2.5- and 7.0-fold from sane to moderately and severely damaged (p<0.0003). AA was decreased in continuously exposed apples (63 vs. 94 nmoles AA/ gFW in control s, p<0.005), but increased 8-fold from sane to severely dam­aged (1'<0.00 1). Continuous sun exposure of fruits from early stages would cause an adaptive response, probably related to an increased synthesis of glutathion and reduction through AA pathway. Non-adapted fruits showing sunburn might be deficient in antioxidant mechanisms to avoid membrane damage, maintaining paradoxically high levels of AST and AA.