干旱与高盐对梭梭叶绿素荧光特性的影响

为了更好地了解梭梭适应极端复杂沙漠生境的生理生态适应机制，在对梭梭幼苗离体脱水胁迫下叶绿素荧光特性研究基础上，应用IMAGING-PAM调制荧光成像系统对梭梭幼苗在模拟干旱、高盐以及与强光并存环境下的叶绿素荧光参数进行了测定与分析。结果表明:干旱和NaCl胁迫对Fv/Fm和qP值没有明显影响；qN值在干旱10 d时无明显变化，而胁迫25 d时则略低于对照水平；但各浓度NaCl胁迫下qN值均明显低于对照水平；从光响应曲线变化来看，干旱和NaCl胁迫下qP值随着光强的增加均表现为降低趋势，但NaCl与高光并存发生时对qP值影响更大；然而，对qN值的影响则截然相反，干旱与高光并存发生时qN值降低，而NaCl与高光并存发生诱导了qN值增加，这与单一NaCl胁迫的影响恰好相反。表明梭梭在极端复杂的沙漠生境中可能具有多种过剩光能耗散机制，保护光合机构免受破坏，使PSⅡ保持较高的电子传递活性，从而维持较高的光合能力。 

Effects of drought and excess salt stress on characteristics of chlorophyll fluorescence of leaves in Haloxylon ammodendron.

To understand the ecophysiological adaptation mechanism of Haloxylon ammodendron to extreme desert conditions with multiple stresses, the paper determines and analyses the parameters of chlorophyll fluorescence kinetics in leaves of seedlings under drought, NaCl, and their combination with high light, using IMAGING-PAM. The results showed that Fv/Fm and qP did not change with either drought or NaCl stresses; qN did not change at 10th day but decreased slightly at 25th day under drought stress compared with control, whereas qN significantly decreased under the enhanced NaCl concentrations. Values of qP tended to decrease with the increase in light intensity under both drought and NaCl stresses, but NaCl in combination with high light intensity had greater influence on qP compared with drought with high light. However, drought in combination with high light led to the decrease in qN, whearas NaCl with high light resulted in the increase in qN. These results suggest that H. ammodendron has multiple pathways to dissipate excessive energy, in order to protect the apparatus of photosynthesis from damages, and keep the higher activities of electric transfer, and maintain higher photosynthetic capacities.