REGULATING EFFECT OF NITROGEN ON GRAIN YIELD AND ANTIOXIDANT DEFENSE OF SUPER AND NON-SUPER FRAGRANT RICE UNDER HIGH SOIL TEMPERATURE

The purpose of this study was to investigate the effects of nitrogen (N) application on the grain yield and antioxidant response in fragrant rice under high soil temperature during the flowering stage. A pot experiment was conducted with two conventional fragrant rice varieties, i.e., super rice variety (Yuxiangyouzhan) and non-super rice variety (Xiangyaxiangzhan) grown under two nitrogen application levels (ZN, 0 g N per 12 kg soil and AN, 1.75 g N per 12 kg soil) as well as two temperature levels (Ambient soil temperature, AT and high soil temperature, HT). The grain yield and antioxidant defense of super and non-super fragrant rice were evaluated. The results showed that significant differences in grain yield and antioxidant defense parameters with regard to the variety, temperature treatment, nitrogen treatment, and their interactions were detected. Compared with ZN, the AN treatment significantly increased the grain yield of Yuxiangyouzhan and Xiangyaxiangzhan by 55.06% and 13.32%, respectively, under AT conditions and by 32.62% and 29.19%, respectively, under HT condition. Besides, the antioxidant parameters varied by variety and temperature treatment at AN treatment. Nitrogen application had a significant effect on Superoxide dismutase (SOD) activity and Catalase (CAT) activity in the leaves. The results of this study confirmed that the N application could regulate grain yield and antioxidant capacity of fragrant rice at flowering stage under HT condition.