中文摘要：

土培盆栽试验下，采用3个氮素吸收效率（NAE）有显著差异的水稻基因型五优244（低NAE）、R83—12（中NAE）和水源349（高NAE）为材料，研究了水稻拔节期根系形态特征和生理特性的基因型差异及其与高效氮索吸收的关系。结果表明，水源349总根长、根密度、根表面积和根干重极显著高于R83．12和五优244，且根系总吸收面积、活跃吸收面积和活跃吸收面积／总吸收面积最大，为高效氮索吸收提供了条件。水源349具有较强的根系耗能、氧化还原力、硝酸还原酶、谷氨酰胺合成酶、谷氨酸合酶和谷氨酸脱氢酶活性，促进根内碳水化合物的合成及氮吸收和同化，提高了根系伤流强度及可溶性糖和游离氨基酸含量，进而显著提高了地上部氮含量和氮积累量。逐步回归表明，拔节期较高的根密度、根系总吸收面积和地上部氮含量是水稻氮索高效吸收的重要特征，可作为水稻氮素高效管理和遗传改良的可靠指标。

英文摘要：

Three rice genotypes differing in nitrogen absorption efficiency （NAE）, namely Wuyou 244 low in NAE, R83- 12 medium in NAE and Shuiyuan 349 high in NAE, were planted in a pot experiment to investigate physiological and morphological characteristics of the roots of these plants growing with optimum nitrogen supply at the jointing stage, and their relationships with NAE. Results showed that Shuiyuan 349 was much higher than R83-12 and Wuyou 244 in total length, density, surface area and dry weight of roots, and the highest in total absorption area （St）, active absorption area （Sa） and ratio of Sa/St of roots, which were essential conditions for efficient nitrogen absorption. Moreover, Shuiyuan 349 was also higher in energy consumption, oxidizing capacity, reducing capacity and activities of nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase in roots, which accelerated carbohydrate synthesis and nitrogen uptake and assimilation in roots, and enhanced bleeding intensity, free amino acid and soluble sugar content in roots, thus resulting in significantly high nitrogen content and accumulation in shoots. Stepwise regression indicated that root density, root total absorption area and nitrogen content in shoots at the jointing stage were the main characters of high efficient nitrogen absorption of rice and could be regarded as reliable indicators for efficient nitrogen management and genetic improvement of rice.