Exogenous Ca2+ Regulating Nitrogen Assimilation for Improving Yield and Quality of Rice under Acid Rain Stress

Abstract

Acid rain threatens crop yield and nutritional quality, and Ca2+ can regulate plant responses to abiotic stresses. To improve the yield and nutritional quality of crops under acid rain stress, we applied exogenous Ca2+ to regulate nitrogen assimilation in rice seedlings under simulated acid rain stress (SAR, pH 4.5 or 3.0), taking yield and nutritional quality of rice as evaluation criteria. We found that Ca2+ (5 mM) maintained the total nitrogen content of rice at the seedling and booting stages to alleviate the inhibitory effect of SAR on rice yield. Meanwhile, Ca2+ improved the activity of glutamate synthase to eliminate the disruption of glutamine synthetase/glutamate synthase balance under SAR. It decreased the efficiency of nitrogen assimilation, thereby reducing the inhibition of essential amino acid content in rice. The mitigation effect on pH 4.5 SAR was better than pH 3.0 SAR. Overall, Ca2+ may reduce the negative effect of acid rain on yield and nutritional quality of crops.