The effect of nitrogen level on rice growth, carbon-nitrogen metabolism and gene expression

Abstract

AbstractAs one of the essential macroelements, nitrogen (N) plays an important role in plant growth and development. In order to know the effect of different N levels on the rice plant growth and carbon-nitrogen metabolism, we analyzed the rice growth phenotype, leaf SPAD value, photosynthesis, carbon-nitrogen metabolic status and gene expression profile under four different N levels (0×N, 0.1×N, 1×N and 5×N). The plant height and dry weight increased with increasing N levels, whereas an opposite trend was observed for the root length, which decreased with increasing N levels. The leaf SPAD value, stem nitrate concentration, soluble proteins, photosynthetic rate, stomatal conductance and total nitrogen concentration increased with increasing N levels, whereas an opposite trend was observed for soluble carbohydrates and carbon/nitrogen ratio which decreased with increasing N levels. Metabolite profile analysis revealed that the low N treatment caused visible decreases in the concentrations of total sugars and organic acids in the leaves, while caused visible increases in the concentrations of total sugars, organic acids and free amino acids in the roots. Gene expression analysis showed that the transcriptional levels of 5 genes (GS1;3, NADH-GOGAT1, NADH-GOGAT2, PEPC4 and PEPC7) altered significantly under four different N levels.