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

通过3个试验研究了水稻籽粒氮素利用效率和生物量生产的遗传变异。(1)1991 - 1994年，参照水稻冠层发育，对日本晴水稻氮素供应与干物质生产力之间的关系进行了四年的定量试验。(2)包括日本和亚洲古老/现代品种在内的64个基因型的NUE比较。(3)比较了1998年8个矮秆、高秆水稻品种及1994、1995年日本晴与中国高产水稻F1的氮素利用规律和干物质生产。(1)日本晴叶片冠层干物质生产力对氮素的响应在4年9个条件（3个施氮量× 3个种植密度）中相当稳定。（2）单位吸氮量的籽粒产量在标准品种日本晴的-35 ~+24%之间，现代高产品种的最高产量主要是靠其高的收获指数。生物产量在-11%~+14%之间，达到日本晴标准，一些中国地方品种的株高较高，高产品种也表现出较高的生产力。(3)氮素在冠层发育过程中在叶面积（LAI）和比叶氮（SLN）含量之间的分配在矮秆和高秆品种间存在差异。这种差异影响干物质生产力。叶面积指数越大，光截获量越大，SLN越高，芸香越高。分别在极低和中等至充足的氮供应下有利于干物质生产。即使在SLN相似的情况下，高产F1水稻的芸香也表现出上级优势，这是由于叶片光合作用中较高的氮利用效率和叶片冠层中较陡的氮梯度。

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.