中文摘要：

本研究旨在探明中籼水稻在品种改良过程中产量与氮肥利用效率的变化特点。以江苏省近70年来不同年代在生产上广泛应用的12个代表性中籼水稻品种（含杂交稻组合）为材料，依据应用年代将其分为20世纪40—50年代、60—70年代、80—90年代和2000年以后4个类型，设置0 N （全生育期不施氮）、MN （全生育期施氮210 kg hm–2）和HN （全生育期施氮300 kg hm–2）3个施氮量处理，研究其产量、氮肥利用效率及其生理特性。结果表明，随品种应用年代的演进，不同年代中籼水稻品种的产量和氮肥利用效率均获得较大提高。2000年以后的品种（超级稻）产量和氮肥利用效率较高，根系性状和叶片光合特性以及氮代谢相关酶活性强是其重要生理基础。超级稻抽穗后根系氧化力和剑叶光合速率下降的幅度较大可能是导致超级稻结实率较低的一个重要原因。提高灌浆中后期超级稻的根系氧化力和剑叶光合速率，有望提高超级稻的结实率。

英文摘要：

Improvement in rice cultivars plays an important role in increasing grain yield. However, little is known about the rela-tionship between yield and nitrogen use efficiency in mid-seasonindica rice cultivar improvement process. In this study, 12 typi-cal cultivars （including hybrid combinations） applied in the production in Jiangsu Province during the last 70 years were used, and classified into four types of 1940–1950s, 1960–1970s, 1980–1990s, and after 2000 （super rice） according to their application times. Three treatments of zero N （0N）, 210 kg ha–1 N （MN） and 300 kg ha–1 N （HN） were designed. The results showed that grain yield and nitrogen use efficiency were progressively increased with the improvement of cultivars under each nitrogen rate. The super rice cultivars had a higher biomass and nitrogen accumulation, higher activities of root oxidation and nitrogen metabolic enzyme and higher leaf photosynthetic rate resulting in higher grain yield and nitrogen use efficiency when compared with any other types of cultivars. The root oxidation activity and photosynthetic characteristics of super rice were the peak at the heading stage, but sharp declined from heading to maturity, which could account for an important physiological reason for a lower filled-grain percentage of super rice. It would be an important approach to further increase grain yield of super rice through in-creasing root activity and leaf photosynthetic rate during grain filling.