吉林省不同年代玉米品种光合生理特性对施氮量的响应

Responses of photosynthetic physiological characteristics of maize varieties released in different decades to nitrogen application rate in Jilin province

明确吉林省不同年代玉米品种产量、叶片氮含量与光合特性对不同氮素用量的响应趋势,对东北地区玉米高产品种选育具有重要的实践意义。本研究以20世纪70年代年以来吉林省大面积推广应用的6个代表性品种为研究对象(1970s:吉单101、中单2号;1990s:四单19、吉单159;2010s:先玉335和农华101),在大田条件下共设置4个氮素水平(0、125、250和375 kg hm^(–2)),分析了氮素施用量对不同年代玉米品种产量、叶片氮含量及光合特征参数等的影响。结果表明,所有氮水平下玉米籽粒产量均随品种更替而提高,现代品种在较高氮水平下(≥250 kg hm^(–2))产量优势更明显,各处理产量的提高主要是单穗粒数和粒重同时增加的结果。当施氮量不高于250 kg hm^(–2)时,各年代玉米品种穗位叶净光合速率(Pn)均随施氮量增加而提高,现代品种显著高于老品种,当施氮量为375kghm^(–2)时Pn均显著降低,降低幅度表现为老品种高于现代品种。而吐丝至蜡熟期,Pn降低幅度随施氮量增加和品种更替而减小。玉米光补偿点、暗呼吸速率在不同时期均表现为2010s最高、1990s次之、1970s最低,其中2010s品种的光补偿点比1990s、1970s品种平均分别提高9.72%、27.84%,暗呼吸速率平均提高7.82%、32.98%。各年代品种比叶重(specific leafweight,SLW)随施氮量增加而提高,同一施氮量下SLW表现为随品种更替而降低。不同品种叶片单位面积氮含量(Narea)均随施氮量增加而提高,不施氮处理老品种显著降低,施氮处理品种间无显著差异。相关分析表明,Pn与SLW呈显著正相关关系,而Pn与Narea之间关系可用二次曲线方程拟合,Pn随Narea增加出现转折的Narea值为1.57g m–2。不同年代品种的光合氮利用效率(PNUE)均随施氮量增加而降低,而较高氮水平下(≥250 kg hm^(–2))PNUE随品种更替而显著提高。综上,在较高氮水平下现代玉米品种比老品种显著增产主要归因于其Pn和PNUE的提高,而Pn和PNUE的提高又与比叶重(SLM)、叶片N含量(Nmass、Narea)等性状密切相关,推荐在玉米品种选育过程中参考。

It is of great practical significance to clarify the response trend of yield,leaf nitrogen content,and photosynthetic characteristics of maize varieties released in different years in Jilin province to different nitrogen levels for the breeding of high-yield maize varieties in Northeast China.In this study,six representative varieties popularized and applied in Jilin province since 1970s were used as the materials(1970s:JD101,ZD2;1990s:SD19,JD159;2010s:XY335,NH101).Field experiments with four nitrogen levels(0,125,250,and 375 kg hm^(–2))were set up to analyze the effects of nitrogen application on the yield,leaf nitrogen content,and photosynthetic characteristic parameters of maize varieties released in different decades.The results showed that maize grain yield under all nitrogen levels increased with the replacement of varieties,and the yield advantage of modern varieties was more obvious under high nitrogen levels.The increase of grain yield under different treatments was mainly due to the simultaneous increase of kernel numbers per ear and kernel weight.The net photosynthetic rate(Pn)of ear leaf increased with the increase of nitrogen application rate at no more than 250 kg hm^(–2),and the Pn of modern varieties was significantly higher than that of old varieties.When the nitrogen application rate was 375 kg hm^(–2),Pn decreased significantly,and the degree of reduction showed that the old varieties were higher than the modern varieties.From silking to dough stage,the decrease of Pn decreased with the increase of nitrogen application and varieties evolution.The light compensation point and dark respiration rate of maize were the highest in 2010s,the second in 1990s and the lowest in 1970s at different stages.Compared with 1990s and 1970s,the light compensation point of maize in 2010s increased by 9.72%and 27.84%on average,and the dark respiration rate increased by 7.82%and 32.98%on average.The specific leaf weight(SLW)of varieties increased with the increase of nitrogen application rate,but SLW decreased with the evolution of varieties under the same nitrogen application rate.The leaf nitrogen content per unit area(Narea)of different varieties increased with the increase of nitrogen application rate,but it was significantly decreased in the old cultivars without nitrogen application,and there was no significant difference among the cultivars treated with nitrogen application rate.The correlation analysis showed that there was a significant positive linear correlation between Pn and SLW,and the relationship between Pn and Narea can be fitted by the quadratic equation,the Narea value of Pn turning with the increase of Narea was 1.57 g m–2.The photosynthetic nitrogen use efficiency(PNUE)of all varieties decreased with the increase of nitrogen application rate,while the PNUE of cultivars at higher nitrogen levels(≥250 kg hm^(–2))increased significantly with the evolution of varieties.Thus,compared with the old varieties,the modern varieties were more beneficial to yield improvement in the higher nitrogen levels(≥250 kg hm^(–2)),which was mainly attributed to the higher Pn and PNUE of the modern varieties,while the increase of Pn and PNUE was closely related to the specific leaf weight(SLM),leaf N content(Nmass,Narea),and other characters,which was recommended for reference in the breeding process of maize varieties.