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

对水稻籽粒氮素利用效率(NUE)和生物产量的遗传变异进行了研究。(1)以1991~1994年的冠层发育为参照，通过四年的试验，量化了日本晴水稻氮素供应与干物质生产力的关系。(2)品种(包括日本品种和亚洲老品种/现代品种)的NUE比较。(3)1998年8个矮秆和高秆品种的氮素利用模式和干物质生产量的比较，以及1994年和1995年日本晴与中国高产F1水稻的氮素利用模式和干物质生产量的比较。(1)日本晴叶冠干物质生产力对氮素的响应在4年中和9个条件(3个氮肥施用量×3个种植密度)中都比较稳定。测定了日本晴对氮素截获和辐射利用效率(RUE)的曲线响应。(2)标准品种日本晴的单位吸收氮粒产量在-35%~+24%之间变化，在现代高产品种中最高，主要是由于它们的高收获指数。生物量产量在-11%~+14%之间，符合日本晴标准，一些中国地方品种个头很高，表现出高产的同时也是高产品种。(3)矮秆和高矮品种在冠层发育过程中叶面积(LAI)和比叶氮素(SLN)含量之间的分配存在差异。这种差异影响了干物质生产力。LAI越大，光截留越大，SLN越高，RUE越高。在氮素有效性极低和中等到充足的条件下，分别有利于干物质生产。在SLN相近的情况下，高产杂交一代水稻表现出比日本晴更好的氮素利用效率，这归因于其叶片光合作用的氮素利用效率较高，叶片冠层的氮素梯度较大。

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.