Dynamic Accumulation And Distribution Traits Of Solutes Participated In Osmotic Adjustment And Ion Balance In Suaeda Glauca Under Salt And Alkali Stresses

Suaeda glauca an alkali resistant halophyte was chosen as our experimental materials. Seedlings were applied with salt stress (150mM, NaCl:Na₂SO4=1:1) or alkali stress (150mM, NaHCO₃:Na₂CO₃=1:1). On the one hand,changes of solute accumulation after stressing (0, 2, 4, 8, 16, 24, 36, 48, 72, 96, 144h) were monitored in order to investigate the dynamic process of osmotic adjustment and ion balance in S. glauca during responding to salt and alkali stresses; on the other hand, various solutes in different parts of S. glauca, for instance young leaf, mature leaf, old leaf, young stem, mature stem and old stem, were determined in order to compare the differences in solute distribution characteristics, osmotic adjustment and ion balance mechanisms in different parts of S. glauca under salt and alkali stresses. Our work revealed the physiological mechanisms in S. glauca responding to salt and alkali stresses more deeply.The results of solute dynamic accumulation experiment showed that different solutes had their own characteristics in dynamic accumulation during responding to salt and alkali stresses; the contributions of different solutes to osmotic adjustment and ion balance were different, and the main osmolytes under both stresses were discrepant too. K⁺,Na⁺,NO₃^- were main osmolytes under both stresses. The contribution of Cl- increased significantly under salt stress, while the same thing happened to organic acids under alkali stress. The contributions of Cl^-, NO₃^- and H2PO4- to negative charge under alkali stress were less than that under salt stress.The results of solute distribution experiment indicated that different parts differed in physiological characteristics during responding to salt and alkali stresses. S. glauca realized osmotic adjustment and ion balance by adjusting the accumulation and distribution of various solutes in vivo. Differences in this adaption mechanism not only existed between salt and alkali stresses but also among different parts. For instance, the Na⁺/K⁺ ratios in the young parts were significantly higher than other parts; the inorganic anion contents in leaf were almost not influenced by alkali stress, but decreased in stem by a large margin; the changes in organic acids contents were insignificant under salt stress, but a significant increment was observed under alkali stress. Our research also demonstrated that the contributions of different solutes to osmotic adjustment and ion balance in various parts varied under different stresses. For instance, Na⁺ was the dominant contributor to osmotic adjustment in leaf under both stresses, while in stem the contribution of NO3- was greater; under salt stress, the contribution of Cl^- to osmotic adjustment in all parts was greater than that under alkali stresses; leaf accumulated massive organic acids under alkali stress, which were not only the largest anion contributor but also the main factors to osmotic adjustment. We found that the main differences in ion balance mechanism between salt and alkali stresses and among various parts were that the sources of anions were different. The differences were mainly reflected in the changes in contribution of organic acids, NO₃^- and Cl^- to negative charge.