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.
