摘要
研究了种植密度对夏播玉米(CF008、郑单958和金海5号)冠层结构及光合特性的影响,目的是通过密度调控,构建高效冠层,发挥品种潜力,同时确立不同夏玉米品种高产高效冠层的定量化技术指标。结果表明,3个夏玉米品种均在中或低密度下(CF008为9.75万珠hm-2和11.25万株hm-2,郑单958为8.25万珠hm-2和9.75万株hm-2,金海5号为6.75万珠hm-2和8.25万株hm-2)构建的冠层较合理,冠层光合性能较高。冠层内透光率、叶夹角、茎粗、叶绿素相对含量(SPAD值)和净光合速率(Pn)均随着密度的增加而降低,说明高密度易造成群体内光分布不合理,导致光合性能的降低。灌浆中期前群体光合势(LAD)和叶面积指数(LAI)均表现为中或高密度条件下较高,而后为中或低密度下较高,并且吐丝后LAD所占比率为中或低密度处理显著高于高密度处理,说明高密度条件下冠层结构不合理,造成生育后期叶片提早衰老。在中或低密度下,群体穗位层透光率较大,吐丝期和灌浆中期分别为13.40%～19.45%和16.19%～21.48%;叶面积发展动态较为合理,吐丝期LAI达5.59～6.75,成熟期仍然保持在2.24～3.68,尤其中上层叶片LAI高值持续期较长;吐丝期中上层叶片Pn达到33.6～43.8μmolCO2m-2s-1;吐丝后的群体LAD较高,特别是中密度下LAD达172.01～235.91m2dm-2,后期光合面积持续时间较长,更有利于玉米产量的提高。
Canopy structure has strong effects on photosynthesis and grain yield in maize（Zea mays L.）.Planting density is one of the most important factors that can regulate canopy structure.Many researches have shown that leaf area index（LAI）and leaf area duration（LAD）increase accordantly with the proper increase of planting density,but the percent transmission decreases sharply under excessive high density,resulting in uneven light distribution within canopy and photosynthesis reduction.We need to know which proper planting densities for cultivars lead to little influence on photosynthesis and higher grain yield in summer maize.However,so far few reports on this topic have been found and no quantitative criteria can be used in evaluating canopy structure of different maize cultivars.Therefore,we conducted an experiment with three cultivars and three planting densities in the field having medium soil fertility and application of 180 kg N ha^-1 in Wuqiao Experimental Station（37°41＇02″N,116°37＇23″E）of China Agricultural University in 2006 to establish such quantitative criteria for high yielding cultivars in North China Plain.The split plot design was employed with main plot of plant density（low,medium,and high respectively）,sub-plot of cultivar（CF008,Zhengdan 958,and Jinhai 5 respectively）,and three replicates in each sup-plot.According to plant type,the densities of three cultivars were 9.75×10^4（low）,11.25×10^4（medium）,and 12.45×10^4（high）plants ha^-1 for CF008;8.25×10^4（low）,9.75×10^4（medium）,and 11.25×10^4（high）plants ha^-1 for Zhengdan 958;and 6.75×10^4（low）,8.25×10^4（medium）,and 9.75×10^4（high）plants ha^-1 for Jinhai 5.The high-yielding canopy structure and photosynthesis were obtained under both low and medium densities of the three cultivars.Percent transmission,leaf angle,and stem diameter decreased with the increase of plant density.The chlorophyll relative content（SPAD）and the rate of net photosynthesis rate（Pn）were the smallest under high density because of the uneven light distribution within canopy.For CF008,SPAD value of ear leaf and the third leaf under ear decreased sharply in later growth stages.LAD and LAI values before mid-filling stage were greater under medium or high densities,while different tendency occurred in the maturity stages.Moreover,the proportion of after-silking LAD was greater under low or medium densities,showing that canopy structure was unsuitable under high density due to early senescence.For Zhengdan 958 and Jinhai 5,LAD after silking was greater than that before silking,which was benefit for high grain yield.Our results confirmed that proper planting density can establish high-yielding canopy structure and improve population photosynthesis and yield in maize.We also obtained a series quantitative criteria for high-yielding canopy structure based on the data from Wuqiao area：percent transmission of 13.40%-19.45% in silking stage and 16.19%-21.48% in mid-filling stage under low or medium densities;LAI of 5.59-6.75 in silking stage and 2.24-3.68 in maturity stage,especially highen in middle and upper leaf layers in maturity stage under low or medium densities;Pn of 33.6-43.8 μmol CO2 m^-2 s^-1 in middle and upper layer leaves in silking stage under low or medium den-sities;higher LAD after silking under low or medium densities,with 172.01-235.91 m^2 d m^-2 under medium density.
出处
《作物学报》
CAS
CSCD
北大核心
2008年第3期447-455,共9页
Acta Agronomica Sinica
基金
国家自然科学基金项目(30571089)
北京农业育种基础研究创新平台项目
关键词
夏玉米
密度
叶面积指数
透光率
净光合速率
Summer maize
Density
Leaf area index
Percent transmission
Photosynthesis
