苗期涝害对夏玉米叶片光合特性的影响

Effects of Waterlogging on Photosynthetic Characteristics of Maize Leaves at Seedling Stage

目的：研究涝害对玉米苗期叶片光合特性的影响。方法：以玉米杂交种隆平206为试验材料,采用盆栽试验,于玉米四叶一心时进行淹水（涝害）处理,分析了玉米苗期叶片光合气体交换参数的变化。结果：苗期涝害显著降低隆平206叶片SPAD值、净光合速率（Pn）、蒸腾速率（Tr）和气孔导度（Gs）等参数。叶片净光合速率在涝害后2 d、4 d、6 d和8 d较对照分别下降23.6%、51.7%、88.7%和94%。玉米涝害处理叶片蒸腾速率、气孔导度的变化趋势与净光合速率基本一致。涝害后2~6 d,叶片胞间CO_2（Ci）浓度随着渍害天数的延长逐渐下降,而在处理8 d后,其浓度较处理前期却显著增高。玉米苗期涝害前期（2~6 d）,随着隆平206叶片净光合速率逐渐下降,叶片气孔导度与胞间CO_2浓度亦显著下降,说明隆平206光合速率的下降主要是叶片气孔限制引起的。苗期涝害后期（6 d之后）,隆平206净光合速率持续下降,而胞间CO_2浓度却升高,说明隆平206在涝害发生后期叶片较低光合作用主要由非气孔因素引起。结论：苗期涝害显著降低玉米叶片净光合速率,原因主要是叶片气孔限制（涝害前期）和非气孔因素限制（涝害后期）。

Objective： To investigate the effect of waterlogging on photosynthetic characteristics of maize leaves at seedling stage. Method： The high yield maize （Zea mays L. ） cultivar Longping 206 was grown in this study. The experiment set up the normal water supply treatment （ Control, the soil relative water content remained at about 75% ） and the waterlogging treatment （ WL, maintained about 5 cm water layer in pots）. Effects of waterlogging at the seedling stage on photosynthetic characteristics of maize leaves were examined in this study. Resuits： Waterlogging significantly reduced the SPAD readings, the net photosynthetic rate （Pn）, the transpiration rate （Tr） and the stomata] conductance （Gs） of leaves at the seedling stage. The net photosynthetic rate of maize leaves decreased by 23.6%, 51.7%, 88.7% and 94% respectively at 2, 4, 6 and 8 days after waterlogging, compared with the control. The variation tendency of transpiration rate and stomatal conductance were very similar to net photosynthetic rate under waterlogging. With the passage of time the intercellular CO2 concentration （Ci） first decreased from 2 to 6 days after waterlogging and then increased at 8 day after waterlogging. The net photosynthetic rate in waterlogging treatment decreased gradually along with prolongation of waterlogging time from 2 to 6 days after seedling waterlogging. At the same time, the stomatal conductance and intercellular CO2 concentration in waterlogging treatment significantly decreased. The net photosynthetic rate of leaves continued to decline from 6 to 8 day after seedling waterlogging, while the intercellular CO2 concentration of leaves was increased significantly. These suggested that stomatal limitations at early （from 2 to 6 days after waterlogging） waterlogging and not stomatal limitations at late （8 day after waterlogging） waterlogging that mainly reduced net photosynthesis rate of maize leaves in Longping 206. Conclusion：The results suggested that it was stomatal limitations at early waterlogging and not stomatal limitations at later waterlogging that declined net photosynthetic rate of leaves of waterlogging treatment.