中文摘要：

选用低产氮低效型、高产氮中效型和高产氮高效型具有代表性的6个粳稻品种，在各自最适氮素水平下，研究了根系形态生理特征的差异。结果表明，较之低产类型品种，高产类型品种在根干重、根体积、根系总吸收表面积、活跃吸收表面积、根系α-NA氧化量及根系伤流强度等方面在各个生育时期均存在着明显的优势，说明生产力的提高伴随着根系形态特征的改善和生理活性的加强。同为高生产力类型品种，因氮利用率的差异根系形态生理特征表现不同。较之高产氮中效类型，高产氮高效型水稻的群体根干重、群体根体积、群体根系伤流强度和根系总吸收表面积均有所降低，而单茎根干重、单茎根体积、单茎根系伤流强度、活跃吸收表面积比及根系α-NA氧化量却有显著或极显著提高。表明适当控制高生产力水稻的群体生长量，促进群体和个体协调发展，着力提高抽穗后单茎根系质量，将是水稻高产和氮高效协调统一的可靠途径。

英文摘要：

The difference of root morphological and physiological characteristics of low-yielding and low N-efficiency, high- yielding and medium N-efficiency, high-yielding and high N-efficiency rice cultivars was investigated using six representative japonica varieties under their optimum N levels. The results showed that the high-yielding genotypes showed distinct advantages over the low-yielding ones in root dry weight, root volume, total and active absorbing surface areas of root system, root oxidation ability of ct-NA, and root bleeding intensity at each growth stage, indicating that the increase of productivity was accompanied by the improvement of root morphological traits and the enhancement of root physiological activities. Cultivars with different N-efficiency displayed diverse root morphological and physiological characteristics, even though they were all on a high-yielding level. Comparing with medium N-efficiency genotypes, the high N-efficiency ones showed lower root dry weight, root volume, root bleeding intensity and root total absorbing surface area for populations, but for single plants, the root dry weight, root volume, root bleeding intensity, active absorbing surface area and α-NA oxidation amount were superior in a significant or extremely sig- nificant degree. The results above suggest that the coordination of high-yielding with high N-efficiency could be achieved through controlling population growth properly, facilitating the concordant development of plant population and individuals, and endeavoring to improve the single stem root quality after heading.