Characteristics of Dry Matter Accumulation and Distribution in Conventional Japonica Rice Cultivars with High Nitrogen Uptake Efficiency

[Objective] The aim was to investigate the characteristics of dry matter accumulation and distribution as well as the main factors influencing nitrogen uptake efficiency in conventional japonica rice cultivars with high nitrogen uptake efficiency,and to provide experimental references for genetic improvements of high nitrogen uptake and use efficiency in conventional japonica rice cultivars,the current study was conducted.[Method] 94 conventional japonica rice cultivars were solution-cultured in 2008 and 2009,respectively.Grain yield,dry matter weight and nitrogen content in individual organs were measured.Based on the amount of nitrogen absorption(ANA),these rice cultivars were clustered into 6 types in the alignment from low to high(A,B,C,D,E and F) by the MinSSw(dynamic clustering method-minimum sum of squares within groups) method.[Result] Great differences in ANA were detected among all tested cultivars.The average grain yields of rice cultivars with high N uptake efficiency were significantly higher than those of rice cultivars with low N uptake efficiency.The rice cultivars with high N uptake efficiency at each growth stage showed higher dry matter accumulation of population and single panicle,and the dry matter weight of root,stem,sheath and leaf as well as panicle were significantly higher than those with low N uptake efficiency,while there was no significant difference in harvest index.Dry matter accumulation at maturity stage had more important effect on ANA than the harvest index.Both of dry matter accumulation before and after heading had important influence on the dry matter accumulation at maturity stage,especially the dry matter accumulation before heading.The dry matter accumulation per single panicle had more important effect on the dry matter accumulation at maturity than the panicle numbers per unit area,the dry matter accumulation per single panicle before heading,especially.The improvement of dry matter accumulation of leaf sheath and stem and panicle weight at maturity was beneficial to improve dry matter accumulation at maturity stage.[Conclusion] The promotion of the dry matter accumulation per single panicle,the dry matter accumulation per single panicle before heading,especially,as well as the promotion of dry matter per leaf sheath and stem heading and after heading and dry matter per panicle after heading can significantly improved the dry matter accumulation per population in the N uptake efficiency of japonica rice cultivars.