中文摘要：

以两个超级稻品种两优培九（两系杂交籼稻）和淮稻9号（粳稻）为材料,两个高产品种汕优63（三系杂交籼稻）和扬辐粳8号（粳稻）为对照,设置四种氮肥水平,即全生育期不施氮肥、全生育期施氮120kg/hm2、全生育期施氮240kg/hm2和全生育期施氮360kg/hm2,分析不同氮肥水平对超级稻产量的影响及其生理机制。结果表明,施氮量为0～360kg/hm2,两个超级稻品种的产量、灌浆期剑叶光合速率和硝酸还原酶活性、根系氧化活力和玉米素＋玉米素核苷（Z＋ZR）含量、地上部干物质量、根干质量和根冠比均随着施氮量的增加而增加。而两个对照品种在施氮量0～240kg/hm2条件下,以上各指标随施氮量增加而增加,当施氮量达到360kg/hm2时,则显著下降。在同一施氮水平下,两个超级稻的产量均高于对照品种,但超级稻的其他各测定指标,在施氮量不高于240kg/hm2时低于对照品种,施氮量为360kg/hm2时高于对照品种。说明超级稻品种无论在低氮还是在高氮水平均能获得较高产量,在高氮水平下更有利于其生理和产量优势的发挥。

英文摘要：

A field experiment was conducted to reveal the effects of nitrogen rate on super rice grain yield and its mechanism with two super rice cultivars,Liangyoupeijiu（two-line indica hybrid）and Huaidao 9（japonica）,and two high-yielding elite check cultivars,Shanyou 63（indica hybrid）and Yangfujing 8（japonica）as material at four nitrogen（N）rates,no N application and N rates of 120kg/hm2,240kg/hm2,and 360kg/hm2.The results showed that the grain yield of two super rice cultivars increased with increasing N rates from 0to 360kg/hm2.Similarly,the physiological performance,such as net photosynthetic rate and nitrate reductase activity of the flag leaf,root oxidation activity and zeatin＋zeatin riboside content,shoot dry weight,root dry weight and the root/shoot ratio were improved with increassing N rates for both super rice cultivars.The grain yield and the physiological performance of the two check cultivars were also improved with the increase of N rates from 0to 240kg/hm2.The above-mentioned indexes were decreased at the N rate of 360kg/hm2 for the two check cultivars.At the same N rate the grain yield of the two super rice cultivars was higher than that of the two check cultivars,while the physiological performance of the super rice cultivars was just the opposite under N rates no more than 240kg/hm2.However,the physiological performance was better for super rice at the N rate of 360kg/hm2.The results suggested that super rice cultivars could obtain a higher grain yield than elite high-yielding cultivars at either a low N rate or a high N rate,and a high N rate was favorable to realize high-yielding potential of super rice.