河套灌区食用向日葵光合作用的光响应曲线分析

Light response curve of edible sunflower photosynthesis in Hetao irrigation district

以食用向日葵为材料,采用开放式气路测定不同发育阶段(两对真叶、13-14片叶、现蕾期、开花期、开花后20d)的净光合速率、气孔导度、胞间二氧化碳浓度、蒸腾速率等相关指标,并运用Michaelis-Menten模型对净光合速率进行了模拟,计算了光响应曲线的特征参数。结果表明:在试验设置光强下,各个生长发育期净光合速率(Pn)随着光合光通量密度(photosynthetic photon flux density,PPFD)的增加而增加,增加幅度随着植株由营养生长到生殖生长达到最大,之后随着叶片的衰老趋于平缓;在河套灌区食用向日葵的整个生育期,表观初始量子效率α大多在0.067～0.083之间变化。最大净光合速率Pmax在14.61～64.16μmol.m-2.s-1之间变化,光补偿点和光饱和点的变化范围分别为41.17～107.83μmol.m-2.s-1和2 382.89～3 600.51μmol.m-2.s-1,表明向日葵具有高光能利用率,是耐阴性较差特别喜光的典型阳生植物。随着光照强度的增加,不同发育期向日葵的净光合速率、气孔导度和蒸腾速率明显增加,而胞间CO2浓度降低。当光强<500μmol.m-2.s-1时,各发育期的WUE(水分利用效率)随光的增加快速上升,但当PPFD>500μmol.m-2.s-1后,两对真叶期仍以较高的速率增加未见减少,其他生长发育期WUE随光强呈现抛物线变化。

Net photosynthetic rate(Pn),stomatal conductance(Cond),intercellular CO2 concentration(Ci) and transpiration rate(Tr) in leaves of sunflower at different development stages(two pairs of leaves,13-14 leaves,bud stage,flowering stage,20d after blossom) were measured in an open-circuit gas channel system.Pn was simulated by Michaelis-Menten model,and then characteristic parameters of the light response curves were calculated.The results showed that Pn increased with increasing PPFD in 0 to 2 000 μmol·m-2·s-1 at each development stages,and the increased rate reached a maximum from vegetative to reproductive growth,then decreased with leaf senescence.During the whole growth period of edible sunflower in Hetao irrigation district,the apparent quantum efficiency mostly in the range of 0.067 to 0.083,the maximum net photosynthetic rate in the range of 14.61 to 64.16 μmol·m-2·s-1,light compensation point and light saturation point were 41.17 to 107.83 μmol·m-2·s-1 and 2 382.89 to 3 600.51 μmol·m-2·s-1,respectively.It was shown that sunflower was the typical light-loving plant with high solar energy utilization efficiency.Pn,Cond and Tr increased significantly with increasing light intensity at different development stages of sunflower,while Ci reduced.When PPFD<500 μmol·m-2·s-1,WUE(water use efficiency) increased rapidly with increasing light intensity;when PPFD>500 μmol·m-2·s-1,WUE still increased at two pairs of leaves stage,but changed as parabola at other developmental period.