NaCl与Ca(NO3)2等渗胁迫对豇豆新老叶光合特性的影响

目的]探索NaCl和Ca(NO_3)_2等渗胁迫对豇豆新老叶光合特性的影响。方法]试验采用营养液基质栽培法,通过测定豇豆新老叶叶绿素和叶绿素荧光参数的动态变化,研究豇豆的光合作用对Ca(NO_3)_2和NaCl等渗胁迫的响应。结果]2种盐处理对老叶的叶绿素含量没有明显影响;在新叶中,叶绿素含量在NaCl胁迫下降低,在Ca(NO_3)_2胁迫下则略有升高。NaCl胁迫明显降低新老叶的PSⅡ最大光合效率(Fv/Fm)和PSⅡ实际光合效率Y(Ⅱ)],对新老叶造成了不可逆光抑制。老叶的光化学淬灭系数(qP)明显降低,新叶qP未有降低,表明新老叶的盐害程度和光保护机理可能不同。在Ca(NO_3)_2胁迫下,新老叶中Fv/Fm与对照无明显差异,且非光化学淬灭系数(qN)都明显升高。这表明Ca(NO_3)_2胁迫对豇豆新老叶片没有造成不可逆性光抑制,新老叶都有通过改变光系统Ⅱ激发能分配方式来适应盐胁迫环境。老叶Y(Ⅱ)和qP处理后期略低于对照,而新叶则无明显变化,老叶受到的盐害较新叶严重。结论]2种盐胁迫未影响老叶叶绿素含量,但老叶的光系统Ⅱ在盐胁迫下受到的伤害较新叶严重,且NaCl胁迫对豇豆幼苗的伤害要大于等渗Ca(NO_3)_2。

Effects of NaCl and Ca(NO3)2 Isotonic Stress on Photosynthetic Characteristics in New Leaves and Old Leaves of Cowpea

Objective]To discuss the effects of isotonic stress of NaCl and Ca(NO3)2 on photosynthetic characteristics in new leaves and old leaves of cowpea.Method]Taking nutrient solution culture method,the response of the photosynthesis of cowpea to Ca(NO3)2 and NaCl isotonic stress was studied by measuring the dynamic changes of chlorophyll and chlorophyll fluorescence parameters of cowpea in this study. Result]Two kinds of salt treatments had no significant effect on the chlorophyll content in old leaves.In the new leaves,chlorophyll content decreased under NaCl stress,and increased slightly under Ca(NO3)2 stress. NaCl stress significantly reduced Fv / Fm and Y(Ⅱ)of the new leaves and old leaves,and caused irreversible photo inhibition to the old and new leaves. qP of the old leaves was significantly reduced,and qPin new leaves was not reduced,indicating that the salt damage degree and the protective mechanism of the new leaves and old leaves might be different.Under the stress of Ca(NO3)2,there was no significant difference in Fv / Fm between the new leaves and old leaves,and qN was significantly increased,indicating that Ca(NO3)2 stress did not cause irreversible photo inhibition of the old leaves and new leaves, and all leaves adapted to the salt stress environment by changing the photosystem Ⅱ excitation energy distribution. Y (Ⅱ)and qP of the old leaves were slightly lower than that of control at late period,while the new leaves had no obvious changes.The old leaves were more severely damaged than the new leaves.Conclusion]Two kinds of salt stress did not affect the chlorophyll content in the old leaves,but the damage of the PSⅡ of old leaf under salt stress was more serious than that of the new leaf,and the damage of NaCl stress to cowpea seedlings was greater than that of Ca(NO3)2 stress under isotonic conditions.