Salicylic acid-induced antioxidant protection against low temperature in cold-hardy winter wheat

``Dongnongdongmai 1'' is a cultivated winter wheat which can endure cold temperature as low as -30 degrees C with a reviving rate of 85 %. We aimed to explore the involvement of antioxidant protection system in salicylic acid (SA)-enhanced cold resistance of winter wheat. Seedlings were prayed with 0.1 mM SA at three-leaf stage, followed by cold acclimation at tillering stage (4 degrees C for 5 days) prior to cold treatment at 4, 0, -10 or -20 degrees C for 2 days. Under low temperature, the relative electrical conductivity (REC) of rhizomes and H2O2 content in rhizomes were lower compared with leaves, while in the reactive oxygen species (ROS) removal system, only the POD activity was higher. Foliar spray with SA significantly inhibited the cold-increased REC of rhizomes at -20 degrees C and REC of leaves at -10 and -20 degrees C. In addition, application of SA prior to -10 or -20 degrees C treatment suppressed the increase in H2O2 content both in rhizomes and leaves. SA enhanced the activities of SOD, POD, and CAT in wheat following low-temperature treatment, especially at -10 and -20 degrees C. In addition, spray with SA resulted in 1.1-to-4.9-fold enhanced activities of the key enzymes in AsA-GSH cycle, including APX, DHAR, and MDHAR. Our results suggested that SA could improve the resistance of winter wheat against extreme low temperature by enhancing the activities of antioxidases to eliminate ROS and maintain the redox homeostasis. In addition, the less damage to rhizomes in comparison with leaves may be attributed to enhanced POD activity.