Effects of elevated nitrogen application on nitrogen partitioning, plant growth, grain quality and key genes involved in glutamate biosynthesis among three rice genotypes

Jun Wang1, Yi-peng Lu2, Jie Wang2, Rui-xin Xu2, Jun Li4, Wei Hu2, Ya-jun Xiong2, Yun-bo Zhang3, Xiao-yan Wang3, and Xiao-hai Tian3*
The N absorption and assimilation is critical for the rice (Oryza sativa L.) yield increase when overdose N was applied in rice production. Three different rice genotypes, ‘Quanliangyou 1’ (Q1), ‘Quanliangyou 681’ (Q681) and ‘Huanghuazhan’ (HHZ), were selected to investigate the effects of elevated N input on the N partitioning, plant growth, grain quality and key genes involved in glutamate biosynthesis. Under increasing N inputs (0, 120, 180, 250 kg ha-1), N content in leaf, culm, seed and root were increased significantly. The increased N was preferentially deposited in leaf and culm. Tiller number, panicle number and length were also proved to be significantly promoted, but plant height and 1000-grain weight were nonsignificantly affected under elevated N input. Under high N input, seed protein content was elevated, while fatty acid and amylose content remained unchanged in comparison to low N input, but amylopectin content decreased. For the key genes in N assimilation, glutamine synthetase (OsGS1;1) could be induced by increasing N input (0 to 180 kg ha-1) but higher N input (250 kg ha-1) inhibit its expression, which showed similar response pattern with the glutamine synthetase activity. Although different rice genotypes showed similar response pattern to elevated N input, each genotype varied a lot in certain phenotypic indexes. And the response pattern of all these phenotypic characteristics to elevated N input was independent of rice genotype. These findings suggest that elevated N input could promote rice growth, reallocate N content in different tissues, and have negative impact on grain quality. This study provided physiological and molecular foundation for rice breeding and cultivation under high N input.
Keywords: Grain quality, growth promotion, nitrogen input, nitrogen partitioning, Oryza sativa, rice.
1Yangtze University, College of Agriculture, Jingzhou, 434025, Hubei, P.R. China.2Yangtze University, Engineering Research Center of Ecology and Agricultural Use of Wetland, Jingzhou 434023, Hubei, P.R. China. 3Yangtze University, Hubei Collaborative Innovation Center for Grain Industry, Jingzhou 434023, Hubei, P.R. China.*Corresponding author (xiaohait@sina.com). 4Guangxi University, College of Agronomy, Nanning, 530005, Guangxi, P.R. China.