Revealing the Effect of Different Nitrogen Fertilizer Levels on Rice Yield through 2 Metabolite Evaluation

Abstract We investigated the differences in metabolites related to rice yield under different nitrogen fertilizer levels and the regulatory roles of key metabolites in metabolic pathways. This study focused on the rice variety Yangchan 15002 and used non-targeted metabolomics methods to detect the metabolic products of rice leaves under three nitrogen fertilizer levels. The yield of Yangchan 15002 plants under high nitrogen (A3: 315 kg hm−2) conditions was significantly higher than that of plants under medium (A2: 270 kg hm−1) and low nitrogen (A1: 180 kg hm−2) conditions. The number of grains per spike in A3 was 6.53% and 18.03% higher than in A2 and A1, respectively. The seed setting rate and thousand-grain weight of plants in the A2 treatment were not significantly different from plants in the A3 treatment. Still, both were significantly higher than A1. The leaf area index and chlorophyll content of plants in A3 were significantly higher than those in A2 and A1. Thirty metabolites related to yield components were identified, among which 4-methylcellulose L-glutamic acid was negatively correlated with C5-branched dicarboxylic acid metabolism and grain number per spike. Triglycerides, L-piperidine, and (S) -2-acetone-2-hydroxybutyric acid were negatively correlated with the number of grains per spike. The increasing application of nitrogen fertilizer improved yield by improving the ear structure of the plants. Specific metabolites in rice leaves are related to the metabolic pathways of amino acid metabolism, carbohydrate metabolism, cofactors, and vitamins under different nitrogen fertilizer conditions. The metabolism of C5-branched dicarboxylic acids in carbohydrate metabolism was significantly positively correlated with the number of grains per spike. These key metabolites are regulated by nitrogen fertilizer and play an important regulatory role in improving the yield and antiaging ability of Yangchan 15002, especially in increasing the number of grains per spike.