| Nirtaria sibirica Pall is a strong xerophytic shrub and halophyte,which is a plant in Nirtaria genus of Nitrariaceae family.The salt tolerance of the N.sibirica is extremely strong,exceeding almost all coastal halophytes.In this study,the effects of different concentrations of GABA(0-15 mmol·L-1)under the salt stress of 100-400 mmol·L-1 on the antioxidant system and the regulation of photosynthesis of the N.sibirica were investigated.The results are as follows:?1?Relative water content of the N.sibirica with the increase of Na Cl concentration showed a trend of gradual decline,were lower than control group in N.sibirica leaf relative water content,when the concentration of Na Cl for 400 mmol·L-1,The N.sibirica appear low relative water content,applying exogenous GABA,when the concentration of Na Cl for 100 mmol·L-1,the concentration of GABA 5 mmol·L-1 reached the best,when the concentration of Na Cl or greater tendency for 200mmol·L-1,the tendency of GABA reached 10 mmol·L-1 reached the highest value.?2?Overall,Malondialdehyde content,superoxide anion(O2·-)content and the content of hydrogen peroxide?H2O2?of N.sibirica,are gradually increased with the concentration of Na Cl shows ascendant trend,a high concentration of Na Cl stress makes the cell membrane of N.sibirica was damaged,accumulation of reactive oxygen species,and a certain concentration of exogenous GABA eased the phenomenon,relieve N.sibirica membranous peroxide level,reduces the O2·-and H2O2 content,and the concentration of GABA is 10 mmol·L-1 ease the most obvious effect.?3?Lower under salt stress(Na Cl?300 mmol·L-1),anti-oxidation protection enzymes SOD,POD activity of N.sibirica showed a trend of rise,when the concentration of Na Cl > 300 mmol·L-1,SOD and POD activity decreased,but not significantly,and the activity of CAT presents ascendant trend with the increase of Na Cl concentration,different concentration of GABA had promoting effect on SOD,POD,CAT activity of N.sibirica,overall,exogenous GABA concentration for 10 mmol·L-1,promoting effect of three antioxidant protection of enzyme are the most obvious.?4?With the increase of Na Cl concentration,the Chl decreased gradually.When Na Cl concentration is 200 mmol·L-1,chlorophyll content has the most obvious alleviating effect at 15mmol·L-1,and when Na Cl concentration is 300 mmol·L-1,chlorophyll content has the most obvious alleviating effect at 10 mmol·L-1,and then decreases.When Na Cl was 300 mmol·L-1 the Pn and Tr values of N.sibirica showed an upward trend with the increase of Na Cl concentration.While Na Cl concentration was 400 mmol·L-1,the decline was significant,Gs value was positively correlated withNa Cl concentration,which reached the maximum when Na Cl concentration was 400 mmol·L-1,However,Ci values tended to decrease first and then increase with the increase of Na Cl concentration.The addition of exogenous GABA significantly promoted the Pn,Gs and Tr of N.sibirica,and alleviated the decline of Ci value.In general,the treatment effect was most obvious when the concentration of GABA was 10 mmol·L-1.?5?With the increase of Na Cl concentration,the values of Fv/Fm,?PSII and q P in the leaves of showed a trend of first rising and then falling,and all reached the maximum when Na Cl concentration was 300 mmol·L-1,the NPQ of N.sibirica value showed an opposite trend with the change of Na Cl concentration.Applying different concentrations of GABA,Fv/Fm,?PSII,q P,ETR value effects are characterized by promoting effect,the optimal promote concentration is not the same and different indicators.The NPQ value of the leaves of N.sibirica decreased to the lowest level at 5 and 10mmol·L-1 with the increase of GABA concentration,indicating that GABA at a certain concentration has a alleviating effect on the NPQ value.?6?The activity of Mg2+-ATPase in the leaves of N.sibirica showed a trend of increasing first and then decreasing with the increase of Na Cl concentration,and the activity of Mg2+-ATPase was not significantly different under different salt concentration stress.After the application of exogenous GABA,different concentrations of GABA can promote the activity of Mg2+-ATPase to different degrees,and the promotion effect is most significant when the concentration of GABA is 10 mmol·L-1.?7?The effect of exogenous GABA on the content of endogenous GABA in Nitraria sibirica: the content of GABA in N.sibirica was positively correlated with the increase of salt concentration.When Na Cl concentration was 300 mmol·L-1,the content of GABA was the highest.When Na Cl concentration was 400 mmol·L-1,GABA decreased,but it was still higher than the control.While Na Cl is 300 mmol·L-1,the concentration of endogenous GABA was positively correlated with that of exogenous GABA,both of which reached the maximum when the concentration of GABA was 15mmol·L-1 and reached the maximum when the concentration of endogenous GABA was 5 mmol·L-1. |
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