Nitrogen Regulates the Grain Yield, Antioxidant Attributes, and Nitrogen Metabolism in Fragrant Rice Grown Under Lead-Contaminated Soil

The aim of this study is to investigate the effect of nitrogen (N) in the regulation of grain yield, growth, and physiology and biochemistry of fragrant rice under lead (Pb) stress. Three fragrant rice cultivars (Daohuaxiang, Basmati, and Yungengyou14) were grown under two N application levels (CK, 0 kg N ha−1, and HN, 200 kg N ha−1) under Pb-contaminated soil. The grain yield, growth, antioxidant attributes, and N metabolism of fragrant rice cultivars were investigated. Results showed that compared with CK, HN treatment increased grain yield in Daohuaxiang, Basmati, and Yungengyou14 by 24.09%, 26.74%, and 23.29%, respectively. Improvement in the effective panicle, grain number per panicle, and 1000-grain weight and agronomic traits under HN treatment was detected. HN treatment decreased the seed setting rate in the three fragrant rice cultivars. In addition, the peroxidase (POD), catalase (CAT), and glutamate synthetase (GOGAT) activity in HN treatment were increased for the three fragrant rice cultivars at both heading stage and maturity as compared to CK. The correlation between the grain yield and the other investigated parameters has also been accessed. Yungengyou14 produced the highest partial factor productivity of N and agronomic use efficiency of N. Those results suggested that N could improve the grain yield resulted from affecting the growth and physiological response of fragrant rice grown under Pb-contaminated soil.