Effects of exogenous salicylic acid on antioxidant activity and proline accumulation in apple (Malus domestica L.)

Abstract

This study was conducted to determine the effects of exogenous application of different levels of salicylic acid (SA; 0 mM, 3.62 mM, and 7.24 mM) on antioxidant activity and proline accumulation in apple (Malus domestica Borkh cv. Red Chief Delicious) trees during late spring frost. The study was performed in Ulukisla, Nigde, Turkey from December 2012 to June 2013. We measured the levels of photosynthetic pigments, total proteins and proline in leaves, as well as superoxide dismutase and peroxidase enzymatic activities. We also performed morphological observations of the trees. The study was planned according to random experimental design. We determined that SA application increased the fruit number, shoot number, and carotenoid contents in the leaves, but this increase was not statistically significant. However, the fruit weights, superoxide dismutase and peroxidase activities, as well as chlorophyll, protein, and proline levels increased significantly in response to SA treatment compared to the control. In addition, the treated fruits were darker than the control. These results suggest that treating apple trees with exogenous SA may increase antioxidant enzyme activities as well as protein and proline levels and may alleviate the effects of late spring frost.