不同CO2浓度对苜蓿分枝期光合性能的影响

以苜蓿（Medicago sativa）‘Maverick’为试验材料，研究不同CO₂浓度下苜蓿分枝期的光合能力日变化情况，探索未来大气CO₂浓度上升过程中苜蓿的生产潜力，为未来牧草种植产业提供指导。结果表明：当开顶式生长室中CO₂浓度为550和700 μmol·mol^-1时，‘Maverick’的叶绿素含量对比室外对照组分别提高了2.4%和3.6%，但差异不显著。净光合速率（Pn）日平均值分别提高了114.69%和116.54%。此外，CO₂浓度升高提高了苜蓿的光系统Ⅱ（PSII）的原初光能转换效率（Fv/Fm）、潜在活性（Fv/Fo）、实际光化学量子产量（Yield），并显著增加了光化学淬灭（qP），降低非光化学淬灭（NPQ）。研究结果表明在高CO₂浓度条件下更利于‘Maverick’叶绿素捕获光能，PSII反应中心比例大，光合作用增强。

Effect of Different CO2 Concentrations on Photosynthetic Performance of Alfalfa During Branching Stage

Under different CO2 concentrations,this experiment studied the diurnal changes of photosynthetic rate and chlorophyll fluorescence parameters of Alfalfa ‘Maverick’ during the branching stage and explored the potential of alfalfa production.It will provide guidance for the forage industry in the process of increasing CO2 concentration in the future.Compared with CK,when the CO2 concentration in the open top chamber (OTC) increased to 550 μmol · mol-1 and 700 μmol · mol-1,the content of chlorophyll increased by 2.4％,3.6％,but the difference was not significant.Net photosynthesis rate (Pn) of alfalfa increased with the increasing CO2 concentration.The daily average values of Pn increased by 114.69％ and 116.54％ when compared with CK.Furthermore,CO2 enrichment increased the light energy transformation efficiency of PS Ⅱ (Fv/Fm),activity potential of PS Ⅱ (Fv/Fo) and actual photochemical efficiency of PS Ⅱ (Yield).Significantly increased photochemical quenching (qP) and reduced non photochemical quenching (NPQ) were observed as well(P＜0.05).The experiment showed that ‘Maverick’ under high CO2 concentration can capture more light energy,increase proportion of PSII reaction centers and have stronger photosynthesis.