水分和CO2浓度对冬小麦气孔特征、气体交换参数和生物量的影响

利用可精准控制CO₂浓度(CO₂])的大型人工气候室, 研究了水分亏缺和CO₂]升高对冬小麦气孔特征、气体交换参数及生物量的影响。结果表明, 水分亏缺导致冬小麦气孔开度减小和气孔空间分布的规则程度降低, 提高CO₂]能够减缓水分亏缺时气孔开度和气孔分布规则程度的下降幅度。与充分灌溉相比, 不同水分亏缺条件下冬小麦的净光合速率、气孔导度和蒸腾速率均显著降低(P<0.05), CO₂]仅可缓解轻度亏水对气体交换过程的影响, 该缓解能力随水分亏缺程度的加剧而降低。水分亏缺降低冬小麦生物量, 但CO₂]升高对水分亏缺时生物量产生的影响不显著(P>0.05)。水分亏缺条件下, 冬小麦通过调整气孔开度和气孔空间分布格局改变叶片的气体交换效率, CO₂]升高对冬小麦产生的“施肥效应”受土壤水分条件的限制。

Effects of Water and CO2 Concentration on Stomatal Traits,Leaf Gas Exchange,and Biomass of Winter Wheat

The experiment was conducted in environmental growth chambers with accurately controlled CO₂ concentrations. Water deficit resulted in the decrease of stomatal openness and more irregular stomatal distribution of winter wheat, and elevated CO₂ concentration (CO₂]) mitigated the negative impacts on the morphological traits of individual stoma and spatial distribution of stomata. The net photosynthetic rate, stomatal conductance, and transpiration rate of winter wheat significantly decreased (P < 0.05) under water deficits than under full irrigation condition, while elevated CO₂] could mitigate the influence of mild water deficit on leaf gas exchange, and this mitigated effect declined with the increase of water deficit degree. In addition, the biomass of winter wheat was substantially decreased with water deficits but barely affected by elevated CO₂] under water deficits. These results suggested that winter wheat changes its leaf gas exchange by adjusting morphological traits of individual stoma and spatial distribution pattern of stomata under water deficit, and the “CO₂ fertilization effect” on winter wheat may be modified by soil water conditions.