Effects of Exogenous Abscisic Acid on Antioxidant System in Weedy and Cultivated Rice with Different Chilling Sensitivity under Chilling Stress

Two chilling-tolerant genotypes, that is, weedy rice WR03-45 and cultivated rice Lijiangxintuanheigu and two chilling-sensitive genotypes, that is, weedy rice WR03-26 and cultivated rice Xiuzinuo were used in this study to investigate the effects of exogenous abscisic acid (ABA) on protection against chilling damage as well as on changes in physiological features. The results showed that under chilling stress the increased levels of superoxide radical (O2 center dot), hydrogen peroxide (H2O2) and malondialdehyde (MDA) in WR03-45 and Lijiangxintuanheigu were lower than those in WR03-26 and Xiuzinuo. Activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR)) and non-enzymatic antioxidants (ascorbate acid (AsA) and reduced glutathione (GSH)) were enhanced in WR03-45 and Lijiangxintuanheigu, whereas they were decreased significantly in WR03-26 and Xiuzinuo. Application of exogenous ABA reduced the chilling damage in the four genotypes. The pre-treatment with ABA decreased the levels of O2 center dot, H2O2 and MDA caused by chilling stress in the four genotypes through increasing the activities of SOD, CAT, APX, GR and the contents of AsA and GSH in the four genotypes under chilling stress. Moreover, pre-treatment with Fluridone, the ABA biosynthesis inhibitor, prohibited the effects of ABA through enhancing the oxidative damages and suppressing the antioxidant defence systems under chilling stress. The results indicate the mechanism for rice with chilling tolerance is to enhance the capacity of antioxidant defence systems under chilling stress. Furthermore, ABA plays important roles in the tolerance of rice against chilling stress for it could induce the capacity of whole antioxidant defence systems including enzymatic and non-enzymatic constitutions under chilling stress.