不同年代育成大豆叶片氮含量的变化及其与净光合速率的关系

为了解大豆品种遗传改良过程中叶片氮含量的变化及其与净光合速率的关系，对吉林省1923年-2004年间育成的21个大豆品种的叶片氮含量和光合特性进行了研究。结果表明，叶片氮含量与育成年代在R2期和R6期呈极显著或显著正相关，但在R4期呈不显著负相关。在R2期和R6期，大豆品种间叶片单位叶面积氮含量增长率明显大于净光合速率增长率，导致了氮素光合利用效率与育成年代呈极显著或显著负相关；在R4期，现代品种叶片单位叶面积氮含量低于老品种，而净光合速率仍高于老品种，导致了氮素光合利用效率与育成年代呈显著正相关。叶片氮含量高，叶绿素含量就高，净光合速率也高，但氮素光合利用效率却低；可将R4期氮素光合利用效率作为高产品种选育的一个指标。  

Changes of nitrogen content in leaf and its correlations with net photosynthetic rate of soybean cultivars released in different years

In order to understand the changes of leaf nitrogen content and its relationship with the net photosynthetic rate (Pn) during genetic improvement of soybean cultivars, leaf nitrogen content and photosynthetic characteristics of 21 Soybean cultivars released from 1923 to 2005 in Jilin Province were studied. The results showed that the leaf nitrogen content had highly significant or significant positive correlation with released years in R2 and R6 stages, but it had no significant negative correlation in R4 stages. The growth rate of nitrogen content per leaf area was significantly higher than the net photosynthetic rate in R2 and R6 stages, resulting in highly significant or significant negative correlation between photosynthetic nitrogen efficiency and released years. But the nitrogen content per leaf area of modern cultivars was lower than the old cultivars in R4 stages, the net photosynthetic rate was still higher than the old cultivars, resulting in a significant positive correlation between photosynthetic nitrogen efficiency and released years. The chlorophyll content and the net photosynthetic rate would be high if the nitrogen content in leaf was high, but the photosynthetic nitrogen efficiency would be low. In R4 stages, the photosynthetic nitrogen efficiency could be a high-yielding cultivars bred indicator.