大气CO2浓度升高与氮肥互作对玉米花后碳氮代谢及产量的影响

[目的]研究大气CO2浓度升高(eCO2)及氮肥施用对夏玉米开花吐丝后不同组分碳氮代谢物含量及动态和产量的影响,为全球气候变化下玉米生理过程及产量形成的变化提供理论支撑,同时为玉米作物模型调参提供实证数据.[方法]利用自由大气CO2富集(FACE)平台,以夏玉米品种农大108为试验材料开展田间试验.在常规大气CO2浓度...

Effects of Elevated Atmospheric CO2 Concentration and Nitrogen Fertilizer on the Yield of Summer Maize and Carbon and Nitrogen Metabolism After Flowering

【Objective】 To provide the theoretical support on the mechanism on the sustainable production of maize under future climate change and give suggestions on associate parameter adjustment for crop models, the effects of elevated atmospheric CO₂ concentrations (eCO₂) and nitrogen application on the content and dynamics of different carbon and nitrogen metabolites after flowering of summer maize were studied. 【Method】 Based on the free atmospheric CO₂ enrichment (FACE) platform, a field experiment was carried out with Nongda 108, a summer maize variety, as the experimental material. Two nitrogen levels (ZN-zero nitrogen and CN-180 kg N·hm^-2) were set under the ambient atmospheric CO₂ concentration (aCO₂) of about (400±15) μmol·mol^-1 and high CO₂ concentration of (550±20) μmol·mol^-1, respectively. The following measurements were monitored in the experiment: the maize yield and its components, accumulation of dry matter, content and dynamics of carbon metabolites, including non-structural carbohydrates (ie. soluble sugar and starch), total carbon and nitrogen metabolites including soluble nitrogen (ie. nitrate nitrogen, free amino acids, and soluble protein), and insoluble nitrogen compounds (ie. cell walls-N, thylakoid-N, and total-N), and the carbon to nitrogen ratio. 【Result】 (1) eCO₂ and nitrogen application could promote the accumulation of biomass of summer maize, however the effects on maize yield and yield components were not significant. (2) Under eCO₂, the concentration of soluble sugar, one of the components of carbon metabolites, showed significant increase in the functional leaves after the flowering stage, as well as the C/N ration at the late seed-filling stage. (3) Under eCO₂, the concentration of essential functional N components did not show obvious variation in the functional leaves after the flowering stage, but the content of some structural nitrogen components were decreased: The content of soluble protein, the functional N component, was not affected by eCO₂ in the functional leaves. The concentration of free amino acid, one of the simple N components, only showed increase at the flowering stage and then showed less change at the later growth period compared with that under aCO₂. However, the content of cell wall-N and thylakoid-N, the non-soluble N components, were significantly decreased at the late period after flowering stage. (4) Nitrogen fertilizer application could increase the concentration of non-structural carbohydrates (soluble sugars) and nitrate-N significantly in functional leaves from tasseling to the later stage of filling, as well as the content of cell wall-N and thylacoid-N. However, the content of soluble protein was not affected in functional leaves without nitrogen application under the medium soil fertility. In comparison, the content of thylakoid-N and cell wall-N showed decrease in the functional leaves in the treatment without nitrogen fertilizer application, implying that nitrogen was usually preferentially supplied for the soluble protein to meet the necessary requirement of crop growth. (5) The interaction function of eCO₂ and nitrogen fertilizer showed difference for varied components of the carbon and nitrogen metabolites, usually exhibited at different stages: combination of N application and eCO₂ improved the concentration of simple carbon and nitrogen components, such as soluble sugars and nitrate nitrogen in the later stage of maize functional leaves, and increased the C/N ration. The content of cell wall nitrogen could be increased at the early stage of grouting for summer maize. For total nitrogen content in functional leaves, it showed decreased only at the later stage of seed filling grouting, and there was no other impact on the total nitrogen at other stages in summer maize growth period. 【Conclusion】 eCO₂ had a certain effect on the biomass increase of summer maize, and the carbon nitrogen ratio of ear to leaf increase significantly in some stages, but had no significant effect on the yield. Under eCO₂, the content of unstructured carbohydrates in ear leaves increased, but the total nitrogen and insoluble nitrogen compounds decreased to different degrees after flowering. Therefore, it was important to increase nitrogen application level rationally under the future climate change scenarios in which eCO₂ would be one of the characteristics.