Comparative Study On The Resistance Of Suaede Salsa L. And Puccinellia Tenuiflora Under Different Concentrations Of NaCl And Na₂ CO₃ Stress

This study tries to explore the impact of NaCl and Na₂CO₃ stress on the growth of Suaeda salsa L. and Puccinellia tenuiflora,through evaluating the effects on seed germination, growth of seedling conditions, physiological characteristics, thermal dissipation, as well as metabolism of reactive oxygen species and photochemical characteristics of PSâ…¡. The main results are as follows:1. Effect of different concentrations of NaCl and Na₂CO₃ on seed germination , the growth of seedling conditions during germination stage and the growth in Suaeda salsa L. and Puccinellia tenuifloraGermination rate of Suaeda salsa and Puccinellia tenuiflora decreased with both of the salts concentrations. The seed germination of Suaeda salsa and Puccinellia tenuiflora under NaCl stress decreased significantly greater than that under Na₂CO₃ stress, indicating that osmotic stress, rather than pH stress, was the main reason for germination inhibition in Suaeda salsa and Puccinellia tenuiflora under both NaCl and Na₂CO₃ stress.The growth of seedling conditions during germination stage and the growth of Suaeda salsa and Puccinellia tenuiflora became weaker with the increase of NaCl and Na₂CO₃ concentrations. And the growth conditions of Suaeda salsa under NaCl stress was better than under Na₂CO₃ stress, On the contrary, the growth conditions of Puccinellia tenuiflora under NaCl stress was worse than under Na₂CO₃ stress.2.Effect of different concentrations of NaCl and Na₂CO₃ on the MDA content of Suaeda salsa L. and Puccinellia tenuiflora.Under NaCl and Na₂CO₃ stress, the MDA content of Suaeda salsa and Puccinellia tenuiflora leaves increased with NaCl and Na₂CO₃ concentrations. But the MDA content of Suaeda salsa and Puccinellia tenuiflora leaves increases less under NaCl than under Na₂CO₃ stress, showing that Na₂CO₃ stress was more seriouse than NaCl stress.3.Effect of different concentrations of NaCl and Na₂CO₃ on the SOD activity in the leaves of Suaeda salsa L. and Puccinellia tenuiflora.Under NaCl and Na₂CO₃ stress, with the salt concentration increasing, the SOD activity of Suaeda salsa and Puccinellia tenuiflora showed different trends. Under NaCl stress, the SOD activity of Suaeda salsa increased firstly and then decreases with the salt concentrations, and peaked at 200 mmol/L, but still higher than CK at 400mM NaCl. For Puccinellia tenuiflora, the SOD activity decreases continuously with the NaCl concentrations. Moreover, under Na₂CO₃ stress, the SOD activity of Suaeda salsa and Puccinellia tenuiflora both decreased significantly with Na₂CO₃ concentrations.4.Effect of different concentrations of NaCl and Na₂CO₃ on the xanthophyll cycle of Suaeda salsa L. and Puccinellia tenuiflora.Under NaCl treatment, with the salt concentration increasing, the de-epoxidation degree of xanthophyll cycle (DPS) of Suaeda salsa decreased firstly and then increased, and significant increased under 300 and 400 mmol/L NaCl. Under Na₂CO₃ stress, the DPS increased gradually but significantly under 75 and 100 mmol/L Na₂CO₃. As for Puccinellia tenuiflora, the DPS increased gradually under NaCl and Na₂CO₃ stress, and increased significantly under 400mM NaCl and 75, 100 mmol/L Na₂CO₃, respectively. All the results implied that the de-epoxidation degree of xanthophyll cycle can play an effective protection on Suaeda salsa and Puccinellia tenuiflora under salt stress.5.Effect of different concentrations of NaCl and Na₂CO₃ on the photosynthetic oxygen evolution rate of Suaede salsa L.and Puccinellia tenuiflora.Under NaCl and Na₂CO₃ stress, with the salt concentration increasing, Suaeda salsa and Puccinellia tenuiflora photosynthetic oxygen evolution rate showed different trends. As for Suaeda salsa under NaCl treatment, the photosynthetic oxygen evolution rate increases first and then decreases with NaCl concentrations, and decreased significantly under 400mM NaCl. Under Na₂CO₃ stress, however, with the increase of Na₂CO₃ concentration, the photosynthetic oxygen evolution rate decreases gradually and significantly under 100 mmol/L Na₂CO₃. As for Puccinellia tenuiflora under NaCl stress, the photosynthetic oxygen evolution rate decreased gradually and significantly under 200, 300 and 400 mmol/L NaCl. Under Na₂CO₃ stress, the trend was the same, with the increase of Na₂CO₃ concentration; the photosynthetic oxygen evolution rate gradually increases, and decreases significantly under 75 and 100 mmol/L concentrations. Comparingly, the salt tolerance of Suaeda salsa is stronger than that of Puccinellia tenuiflora, and the alkali tolerance of Suaeda salsa is weaker than that of Puccinellia tenuiflora.6.Effect of different concentrations of NaCl and Na₂CO₃ on the Chlorophyll fluorescence parameters of Suaeda salsa L. and Puccinellia tenuiflora.Under NaCl stress, Fo of Suaeda salsa decreased firstly and then decreased, while Fv/Fm of Suaeda salsa increased firstly and then decreased, but all not significant, indicating that the photosynthesis centers of Suaeda salsa were not damaged by NaCl, the potential photochemical efficiency of PSâ…¡was not obviously affected. However, under Na₂CO₃ stress, Fo increased continuously with the alkali concentrations, and Fv / Fm decreased continuously simultaneously, indicating that the reaction center was affect by high Na₂CO₃ concentrations. Under NaCl and Na₂CO₃ stress, Fo of Puccinellia tenuiflora increased and Fv/Fm decreased continuously and significantly with concentrations, Indicating that photosynthesis center of Puccinellia tenuiflora was significantly damaged under NaCl and Na₂CO₃ stress, the potential photochemical efficiency of PSâ…¡decreased significantly.7.Effect of different concentrations of NaCl and Na₂CO₃ on the photochemical characteristics of PSâ…¡in Suaeda salsa L. and Puccinellia tenuiflora.Wk accounts for K-phase variable fluorescence (FJ-FO) amplitude ratio, it can indicate that the reaction center has been damaged with the salt concentration increasing.The Wk of Suaeda salsa increases more than it of Puccinellia tenuiflora with the NaCl concentration increasing.On the contrary, the Wk of Suaeda salsa increases less than it of Puccinellia tenuiflora with the Na₂CO₃ concentration increasing.With the NaCl treatment, Sm, N and VJ of Suaeda salsa change less than them of Puccinellia tenuiflora, but Sm, N and VJ of Suaeda salsa change more than them of Puccinellia tenuiflora with the Na₂CO₃ concentration increasing. With the NaCl treatment, the RC/CSo of Suaeda salsa increased firstly and then decreased slightly at 300 and 400 mM NaCl compared with CK, and the change was not obvious. Meanwhile, ABS/RC,TRo/RC,ETo/RC,DIo/RC and dVG/dto decreased firstly and then increased slightly at 300,400 mmol/L NaCl. But them of Puccinellia tenuiflora showed opposite tendency.And them of Suaeda salsa changed less than them of Puccinellia tenuiflora. On the contrary, them of Suaeda salsa changed more than them of Puccinellia tenuiflora with the Na₂CO₃ concentration increasing.Under NaCl and Na₂CO₃ stress, it is indicated that the salt tolerance of Suaeda salsa is slightly stronger than it of Puccinellia tenuiflora and the alkali tolerance of Suaeda salsa is slightly weaker than it of Puccinellia tenuiflora from the provide side, receptor side and the reaction center of PSII.In short, seed germination of Suaeda salsa and Puccinellia tenuiflora were inhibited mainly by osmotic stress, not pH. Furthermore, the salt tolerance of S. salsa was slightly stronger than Puccinellia tenuiflora and the alkali tolerance of Puccinellia tenuiflora was slightly stronger than S. salsa by the study of physiological and photochemical characteristics of Suaeda salsa and Puccinellia tenuiflora.