摘要
摘要:为阐明大气CO₂浓度升高和氮肥交互作用对C₄作物玉米光合生理和产量的影响，本研究利用自由大气CO₂富集（FACE）平台，以玉米品种‘郑单958’为试验材料，在不同施氮量[常氮180 kg（N）·hm^-2、低氮72 kg（N）·hm^-2]下比较大气CO₂浓度[（400±15）μmol·mol^-1]和高CO₂浓度[（550±15）μmol·mol^-1]对玉米生长的影响。结果表明：1）大气CO₂浓度升高使玉米苗期叶片叶绿素浓度显著（P=0.025）增加9.5%，抽雄期净光合速率显著（P=0.009）增加9.0%；低氮和常氮下，高CO₂浓度使玉米各主要生育期胞间CO₂浓度分别显著增加34.8%~48.5%和40.0%~49.4%，气孔导度在大口期和抽雄期分别显著下降21.6%（P=0.015）和22.1%（P=0.010），玉米叶片水分利用效率在大口期、抽雄期和灌浆期分别显著增加12.9%（P=0.002）、9.8%（P=0.019）和18.8%（P=0.001）；高CO₂浓度使玉米非光化学淬灭呈降低趋势、PSII有效光化学量子产量有增加趋势；相同氮水平下，高CO₂浓度对玉米产量没有显著影响。2）高CO₂浓度和合理施氮交互作用对玉米功能叶叶绿素含量、净光合速率、PSⅡ有效光化学量子产量增加有一定的促进作用，如在大口期和抽雄期，常氮+高CO₂浓度处理叶绿素含量比低氮+大气CO₂浓度处理增加17.3%和10.7%，高CO₂浓度和合理施氮量交互作用有增加玉米产量的潜力，合理增加施氮量促进了CO₂肥效的发挥。在未来大气CO₂浓度升高条件下合理施氮对C₄作物玉米生长发育有促进作用。
Abstract:Since the industrial revolution, the concentration of atmospheric CO₂ has increased from 280 μmol·mol^-1 to 400 μmol·mol^-1. Nitrogen is a necessary element for many important enzyme-mediated processes in plant growth and is the primary nutrient needed for plant growth. Among different C₄ crops grown worldwide, including China, maize is the most widely planted crop. Clear answers regarding the effect of elevated atmospheric CO₂ concentration (eCO₂) on corn growth and the interaction between eCO₂ and nitrogen fertilizers (N) are yet not to be attained. Studying the impact of eCO₂ on maize growth under different nitrogen supply conditions is important to assess the role of climate change in the C₄ crop growth. A Free Air CO₂ Enrichment (FACE) facility was used in this experiment. The FACE facility has six octagon loops for eCO₂, (550±15) μmol·mol^-1, and six additional octagon loops for ambient CO₂ concentration of (400±15) μmol·mol^-1 (aCO₂); three of which are eCO₂ experimental loops and the other three are aCO₂ experimental loops applied with conventional nitrogen fertilizer, 180 kg(N)·hm^-2 (CN). The rest are low nitrogen, 72 kg(N)·hm^-2 (LN), application treatments. Twelve experimental loops were arranged randomly in the maize field, with the plants spacing of 25 cm and a rows spacing of 60 cm. Results showed that under eCO₂, the chlorophyll concentration of maize seedling leaves increased significantly by 9.5%, and the net photosynthetic rate increased by 9.0% at the tasseling stage. During the maize growth period, eCO₂ significantly enhanced the intercellular CO₂ concentration by 34.8%-48.5% and 40.0%-49.4% under low nitrogen and conventional nitrogen application conditions, respectively. In addition, the stomatal conductance decreased by 21.6% and 22.1% at the 12-leaf and the tasseling stages, respectively. As a consequence of decreased stomatal conductance, the efficiency of water consumption in maize leaves increased by 12.9%, 9.8%, and 18.8% at the 12-leaf stage, tasseling stage and filling stage, respectively. eCO₂ also decreased Non-Photochemical Quenching (NPQ), and increased PSⅡ effective photochemical quantum yield (F_v'/F_m') value. At the same nitrogen fertilizer (N) level, eCO₂ had no significant effect on the maize yield. Secondly, the interaction of eCO₂ and a reasonable increase of N application rate promoted the chlorophyll content, net photosynthetic rate, and F_v'/F_m' of maize functional leaves. For instance, the chlorophyll content of functional leaves for CN-eCO₂ against LN-aCO₂ increased by 17.3% and 10.7%, respectively, at the 12-leaf and tasseling stages. The combination of eCO₂ and a reasonable increase in the N application achieved the maximized maize yield, indicating the promotional effect of N application under the eCO₂ conditions. Appropriate application of nitrogen fertilizer has the potential to promote the growth and development of maize crop under eCO₂ conditions in future.



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