中文摘要：

为了解不同氮素光合效率大豆品种生理特性和产量对氮水平的响应,从R2期到R6期,在5个氮水平下,对2个氮素光合效率高的品种和2个氮素光合效率低的品种的根系活力、叶片硝酸还原酶活性、全氮含量、叶绿素含量、净光合速率、单株干物重和产量进行了研究。结果表明：随氮水平的变化,4个大豆品种的生理特性和产量均表现为低氮促进、高氮抑制的先增加后降低的单峰曲线变化。相近年代育成的不同氮素光合效率品种的比较表明,高氮素光合效率品种的根系活力、叶片硝酸还原酶活性、叶片净光合速率、单株干物重等指标均在中、低氮（40～80 kg.hm-2）处理阶段高于低氮素光合效率品种,在高氮（120～160 kg.hm-2）处理阶段低于低氮素光合效率品种,此差异在R6期达极显著水平（P〈0.01）,在R2期和R4期多为显著（P〈0.05）或不显著水平;叶片全氮含量和叶绿素含量则在所有氮水平均表现高氮素光合效率品种显著低于低氮素光合效率品种。因此,高氮素光合效率品种宜施用中、低量氮肥,而低氮素光合效率品种可相应提高氮肥施用量。

英文摘要：

In order to understand the response of some physiological characteristics and yield to nitrogen levels in soybean va- rieties with different nitrogen photosynthetic efficiency, the study on the root activity, nitrate reductase activity, nitrogen content of leaf, chlorophyll content, net photosynthetic rate, dry weight of single plant and yield of two high-level and two low-level ni- trogen photosynthetic efficiency varieties under five nitrogen levels from R2 to R6 stage was conducted. The results showed that the change in physiological characteristics and yield of four soybean varieties showed a single peak curve which were increased at the beginning and then decreased with the nitrogen levels. The comparisons of different nitrogen photosynthetic efficiency va- rieties released in similar years showed that the root activity, nitrate reductase activity, net photosynthetic rate, dry weight of soybean varieties with high level nitrogen photosynthetic efficiency was higher than low level varieties at low nitrogen （40- 80 kg. ha-＇ ） treatment, but it was lower than the low level varieties at high nitrogen （ 120-160 kg. ha- ~ ） treatment, the differ- ences reached extremely significant level（P 〈0.01 ）at R6 stage ,and they were significant（ P 〈0.05 ）or non-significant at R2 stage and R4 stage. Total nitrogen content and chlorophyll content in leaves of varieties with high level of nitrogen photosynthet- ic efficiency were significantly lower than the low level in five nitrogen levels. So the medium and low amount of nitrogen fertil- izer should be applied for varieties with high nitrogen use efficiency, similarly, increasing the corresponding amount of fertilizer to apply for varieties with low nitrogen use efficiency was feasible.