Effect of Freezing Stress on Lipid Peroxidation and Antioxidant Enzyme Activities of Olive cvs. ‘Fishomi’ and ‘Roughani’

Changes in freezing injury percentage, lipid peroxidation (malonaldehyde formation), antioxidant enzymes activity and proline content were monitored in the leaves of olive cvs. ‘Fishomi’ and ‘Roughani’ under different freezing temperatures (-5, -10, -15 and -20°C for 10 h). The results showed that freezing injury (determined by electrolyte leakage analysis) and malonaldehyde (MDA) content of cv. ‘Fishomi’ were significantly lower than of cv. ‘Roughani’ ones. The activities of peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and polyphenol oxidase (PPO) enzymes of cv. ‘Fishomi’ were signifi cantly higher than those of cv. ‘Roughani’. However, superoxide dismutase (SOD) activity of cv. ‘Roughani’ was higher than of cv. ‘Fishomi’. The proline accumulated in leaves of cv. ‘Fishomi’ was significantly higher than of cv. ‘Roughani’ during freezing stress. The results demonstrated that freezing injury percentage was positively correlated with ion leakage percentage and MDA content in both cultivars. In contrast, SOD, APX and CAT activities and also proline content were negatively correlated with freezing injury percentage. There was a significant negative correlation between PPO activity and freezing injury in cv. ‘Fishomi’. It can be concluded that the lower freezing injury percentage, ion leakage, and MDA content followed by the higher antioxidant enzyme activates as well as proline content in cv. ‘Fishomi’ is a consequence of more effective protective mechanisms.