A study on nitrogen utilization pattern and its efficiency in dry matter production in rice crop

为确定水稻籽粒和生物量生产中氮素利用效率的遗传变异，进行了3项研究。(1) 1991 ~ 1994年以冠层发育为参考，进行了4年氮素供给与水稻干物质生产力关系的定量试验。(2)日本和亚洲老/现代品种64个基因型氮肥利用率比较。(3) 1998年8个矮高品种间氮素利用格局和干物质产量的比较，1994年和1995年日本与中国高产F1水稻间的比较。(1)在4年和9个条件（3施氮量* 3种植密度）下，日本裸叶冠层干物质生产力对氮的响应相当稳定。(2)氮素吸收产量在标准品种“日本”的- 35% ~ +24%之间变化，现代高产品种的产量最高，主要表现为收获指数高。生物量产量为日本标准的- 11% ~ +14%，部分高株中国地方品种表现出高产和高产的特点。(3)矮高品种冠层发育中氮在叶面积（LAI）发育和比叶氮（SLN）含量之间的分配存在差异。这种差异影响干物质生产力。更大的LAI导致更大的光拦截，更高的SLN导致更高的RUE。在极低氮效价和中至足氮效价条件下有利于干物质生产。在相同的单氮条件下，高产水稻的净氮利用率也高于粳稻，这可能是由于叶片光合作用中氮的利用效率更高，叶片冠层中氮的梯度更陡。

Three studies were conducted to determine genetic variability of nitrogen use efficiency (NUE) in grain and biomass production in rice crop. (1) Experiments during four years to quantify the relationship between N supply and dry matter productivity in Nipponbare rice with reference to canopy development from 1991 to 1994. (2) A comparison of NUE among 64 genotypes including Japanese and Asian old/modem cultivars. (3) Comparisons of nitrogen utilization pattern and dry matter production among 8 cultivars with short and high statures in 1998 and between Nipponbare and a high-yielding F1 rice from China in 1994 and 1995.(1) The response of dry matter productivity to N in the leaf canopy of Nipponbare was fairly stable across the four years and the nine conditions (3 N fertilizations * 3 planting densities). Curvilinear responses to N of light interception and radiation-use efficiency (RUE) were determined, (2) Grain yield per unit absorbed N varied from -35 to +24% to the standard cultivars Nipponbare and highest in the modem high-yielding cultivars mainly by their high harvest indices. Biomass yield ranged from -11 to +14% to Nipponbare standard and some Chinese local cultivars with very tall stature showed high productivity as well as the high-yielding cultivars. (3) N allocation in canopy development between leaf area (LAI) development and specific leaf N (SLN) content varied between short and high statured cultivars. This difference affected dry matter productivity. Greater LAI resulting in greater light interception and higher SLN resulting in high RUE. favored dry matter production under very low and medium to sufficient N availability, respectively. High-yielding Fl rice showed superior RUE than Nipponbare even at the similar SLN and this was attributed to higher N use efficiency in leaf photosynthesis and steeper N gradient in the leaf canopy.