Optimizing nitrogen distribution in source‐sink organs at heading for high grain yield and high nitrogen use efficiency in Japonica rice

Abstract

AbstractJaponica rice (Oryza sativa L.) plants with large source (dry matter) and great sink (spikelets per unit area) have higher yield and nitrogen‐use efficiency (HYNUE) than Japonica rice plants with small source–sink characteristics. Nitrogen (N) distribution traits between source and sink organs at heading can be important HYNUE factors for Japonica rice. Two Japonica rice cultivars of Yongyou1540 (large source–sink sizes) and Zhendao18 (small source–sink sizes) were tested with N fertilizer treatments in field experiments. The results indicated that the N content ratios of source organs to panicle organ were increased with increasing N input for both cultivars. Moreover, the greater yield was associated with higher N content ratios of source organs to panicle organ across cultivars and N treatments. However, these parameters were negatively correlated with nitrogen partial factor productivity (PFPN) and nitrogen agronomic efficiency (NAE). Grain yield was positively determined by the ratio of nitrogen concentration in the leaf to nitrogen concentration in the panicle at heading (NcLPr.H). The nitrogen content distributed from the stem organ per spikelet (SSr) and N concentration in leaf organ were the main factors that negatively regulated PFPN and NAE, respectively. In addition, Yongyou1540 had a significantly higher NcLPr.H and lower SSr than Zhendao18 across N treatments (P <.01), which explained why Yongyou1540 had a higher yield and greater PFPN than Zhendao18. These results implied that high NcLPr.H and low SSr may be key factors for the HYNUE formation in Japonica rice with a large source–sink cultivar.