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.