中文摘要：

选用氮素利用高效型和低效型具有代表性的12个粳稻品种,研究了225kg hm^-2施氮条件下根系形态和生理指标的差异及其与氮素利用效率的相互关系。结果表明,有效分蘖临界叶龄期、拔节期、抽穗期和成熟期,氮高效型水稻的根干重、根系体积、总吸收表面积、活跃吸收表面积和活跃吸收表面积比均显著或极显著大于氮低效型水稻。有效分蘖临界叶龄期和拔节期,氮高效类型水稻的根冠比显著大于氮低效型,而抽穗和成熟期则表现相反趋势。成熟期前,氮高效型水稻的根系α-NA氧化量极显著大于氮低效型,而成熟期,氮高效型中杂交水稻的根系α-NA氧化量略低于个别氮低效型水稻品种。相关性分析表明,有效分蘖临界叶龄期、拔节期、抽穗期和成熟期,水稻的根干重、根系体积、根系的α-NA氧化量、总吸收表面积、活跃吸收表面积和活跃吸收表面积比与氮素利用效率呈显著或极显著正相关。有效分蘖临界叶龄期和拔节期,植株的根冠比与氮素利用效率呈显著正相关,而抽穗和成熟期则呈极显著负相关。氮高效型水稻在其一生中具有良好的根系形态和保持较强的根系活力,为植株大量吸收和高效利用氮素奠定了良好基础。同时,在水稻的生长过程中,地下部与地上部的合理比例及协调生长也是促进植株高效吸收利用氮素的重要因素。

英文摘要：

Nitrogen is the most important input required in rice production although over use of N causes so many environment problems.It is well known that N use efficiency is varied in different rice genotypes.Therefore,it is important to explore and exploit the potential contributing to the N use efficiency.As an integral part of plant organs,rice root plays an important role in absorption and utilization of N from soil and fertilizer.In this research,a field experiment with 225 kg ha^-1 N fertilizer application was carried out in 2006 on the farm of Yangzhou University,Jiangsu province,China.A total of 12 rice genotypes（6 N-efficient and 6 N-inefficient）selected from 120 rice cultivars grown in Yangzhou during 2004 and 2005 were adopted to investigate the characteristics of root morphology and physiology in rice types with different N use efficiencies.Relationship between N use efficiency and indexes of root morphology and physiology was also analyzed.The results showed that at different growth stages,the indexes of root morphology and physiology including the root dry weight,root volume,total absorbing surface area of root,active absorbing surface area of root,ratio of active absorbing surface area to total absorbing surface area in N efficient rice type were obviously higher than those in N inefficient rice type.At the critical stage of productive tillering and the stage of elongating,the ratio of root to shoot in N efficient rice type was significantly higher than that in N inefficient rice type while the trend was contrary at the stages of heading and maturing.Before the stage of maturing,the root oxidation ability of α-NA in N efficient ricetype was superior to that in N inefficiency rice type while at the stage of maturing the root oxidation ability of α-NA in N efficient hybrid rice was appreciably lower than that in some N efficient rice cultivars.N use efficiency positively correlated to all the above morphological and physiological indices at all growth stages,with the exception of negatively correlation