冬小麦叶片光合特性对除草剂世玛的响应及其机理

Response of Leaf Photosynthesis of Winter Wheat to Sigma and Its Mechanism

为了探明冬小麦对除草剂世玛的光合响应及其机理,在不同浓度世玛处理下,测定小麦叶片净光合速率（Pn）、初始荧光（Fo）、最大荧光（Fm）、PSⅡ最大光化学效率（Fv/Fm）和PSⅡ潜在活性（Fv/Fo）等光合、叶绿素荧光参数的日变化,并对其差异进行比较。结果表明,（1）冬小麦净光合速率的日变化均呈双峰曲线,有明显的光合＂午休＂现象,随着世玛浓度的升高,Pn显著下降。（2）Fo、Fm、Fv/Fm及Fv/Fo日变化均呈高-低-高的变化趋势,其中对照的Fo以13∶00时最低;而世玛处理后的Fo最低点均推后到17∶00;各处理的Fm以13∶00~15∶00最低;与PAR呈正相关（r=0.730,P〈0.05）;Fv/Fm和Fv/Fo值随着世玛浓度的升高而下降,11∶00时最低。（3）失活的PSⅡ反应中心数量（Fi-Fo）随世玛浓度的升高显著下降,QA的还原速率显著升高。拔节后,4.5 mL.hm-2浓度的世玛处理对冬小麦的安全性较高;大于4.5 mL.hm-2浓度处理下,冬小麦倒二叶光合作用PSⅡ电子传递受阻,PSⅡ反应中心的失活降低了光合作用速率,导致植株生长受到抑制。

Winter Wheat was treated with different sigma concentrations stress after elongation period,then the net photosynthetic rate（Pn）,original fluorescence（Fo）,maximal fluorescence（Fm）,PSⅡmaximum photochemical efficiency（Fv/Fm）and PSⅡpotential activity（Fv/Fo）were measured and their variations were compared to reveal the response and the mechanism of winter wheat to sigma The result indicated that,（1）the curve of diurnal changes of Pn presented two peak values,and the phenomenon of photosynthetic midday depression of leaf happened at noon.Accompanied by the raise of concentrations of sigma stress,Pn declined markedly.（2）The diurnal changes of Fo,Fm,Fv/Fm and Fv/Fo showed all high-low-high tendency.The nadir of control group＇s Fo were measured at 13∶00,sigma stress back to at 17∶00;The nadir of each treatment＇s Fm were measured at 13∶00-15∶00,The diurnal changes of Fm was positively correlated with PAR,and the correlation coefficients were 0.730（P0.05）;the nadir of each treatment＇s Fv/Fm and Fv/Fo were measured at 11∶00,Along with the increase of concentrations of sigma stress,Fv/Fm and Fv/Fo declined.（3） Amount of inactive PSⅡreaction centers（Fi-Fo） declined markedly and QA reduction rate rised markedly,At the period of elongation,The winter is very good at the treatment of 4.5 mL·hm-2 concentration of Sigma treatment;while the concentrations of sigma stress were over 4.5 mL·hm-2,which led to disruption of electron transport of PS II photosynthetic,inactivation of PS II reaction center and reduction of net photosynthetic rate,and resulted stunted growth.