Study On The Saline-alkali Tolerance And Biological Improvement Effect Of Echinochloa Frumentacea

Biologically improvement of saline-alkali soil is a good improvement measure for ecological,social and economic benefits.Chinochloa frumentacea is a pioneer plant for improving saline-alkali soil which has excellent characteristics of tolerance to barrenness,water logging and saline-alkali.However,there have been few reports on the mechanism of salt-alkali tolerance and the effect of improving saline-alkali soil.Therefore,this study had adopted laboratory and trial experiments to study the growth characteristics and physiological characteristics of chinochloa frumentacea on the seed germination and seedling stage under salt-alkali stress.in addition,the study had researched the improvement effect of saline-alkali soil by planting chinochloa frumentacea.The main results showed that:1.The seed germination of chinochloa frumentacea had the strongest tolerance to Na2S04 and the weakest tolerance to Na2CO3.Among them,under the stress of NaCl and Na2SO4,it exhibited the phenomenon of"low promoting high inhibition",and the stress had greater impact on the growth of radicles than embryos.When the concentration of NaCl and Na2SO4?0.5%,the germination potential,germination index,and vigor index of seeds has been increased,the germination time has been shortened.And when the concentration was greater than the value,the indexes were gradually decreasing;With the increase of NaHCO3 and Na2CO3 concentration,all of germination indexes were gradually decreasing and the time of germination has been prolonged.With the concentration of four kinds salt was increased,the decrease of radicle length was greater than that of embryo.The critical concentration of NaCl,Na2SO4,NaHCO3 and Na2CO3 for seed germination of chinochloa frumentacea were 1.64%,2.96%,1.09%and 0.73%respectively.2.Different salinity have been different effects on the growth index at seedling stage of chinochloa frumentacea.Among them,all of indexes showed an increasing tendency under lower concentration of Na2SO4 stress.Compared with control,The plant height,the root-to-shoot ratio,fresh-dry ratio and plant water content were increased by 2.69%,3.21%,1.67%and 0.08%when Na2SO4 concentration was 0.3%.Compared with the control,the plant height increased by 0.69%when the NaCl concentration was 0.3%,and the root-to-shoot ratio,fresh-dry ratio and plant water content showed a downward tendency.The four growth indexes showed a decreasing tendency under NaHCO3 and Na2CO3 stress.The critical concentration of seedling growth for NaCl,Na2SO4,NaHCO3 and Na2CO3 were 1.71%,2.96%,1.66%and 1.48%respectively.3.Different salinity have been different effects on the photosynthesis of chinochloa frumentacea seedlings.Among them,it had strong resistance to photoinhibition and photooxidation under Na2SO4 stress.With the salt concentrations increased,the chloroplast pigment content and initial fluorescence(F0)have showed a first increasing and then decreasing tendency.net photosynthetic rate(Pn),PS? potential activity(Fv/Fm)and PS? maximum photochemical quantum yield(Fv/F0)have showed a decreasing tendency.Stomatal conductance(Gs),intercellular CO2 concentration(Ci),transpiration rate(Tr)and maximum fluorescence(Fm)were gradually decreasing under the stress of neutral salt(NaCl,Na2SO4),while under alkaline salt(NaHCO3,Na2CO3),These indicators showed a tendency of first increasing and then decreasing.F0,Fm,Fv/Fm and Fv/F0 did not have significantly difference with the control under Na2SO4 stress.The net photosynthetic rate of chinochloa frumentacea was mainly limited by stomatal factors under neutral salt stress,however,it was mainly limited by non-stomatal factors under alkaline salt stress.4.Proline content,soluble sugar content and superoxide dismutase(SOD)activity played a major role in the physiological mechanism of chinochloa cea seedlings' salt-alkali tolerance,and it was showed a gradual decreasing under the stress of neutral salt(NaCl,Na2SO4),while under alkaline salt(NaHCO3,Na2CO3)SOD was showed a tendency of first increasing and then decreasing.However,under saline-alkali stress,its were all higher than the control in different degrees.The activities of peroxidase(POD)and catalase(CAT)under the four salt stresses were all increased first and then decreased.The POD activity was significantly lower than the control when the neutral salt concentration was 1.2%and the alkaline salt concentration was 0.8%;the CAT activity was significantly lower than the control when the neutral salt concentration?0.9%and the alkaline salt concentration?0.6%.The K+content of leaves increased when the NaCl concentration was 0.3%compared with the control.5.The distribution and accumulation of K+ and Na+in different parts of chinochloa frumentacea under different salt treatments were different,and the roots of chinochloa frumentacea had a strong ability to accumulate Na+and selectively transport K+.The K+content in leaves and stem sheaths was increased when the Na2SO4 concentration was 0.3%,and the K+content of leaves were increased when the NaCl concentration was 0.3%compared with the control.The K+content in leaves and stem sheaths showed a decreasing tendency under NaHCO3 and Na2CO3 stress.The K+content in the root system was higher than the control when the concentration of Na2SO4 and NaCl was 0.3%,and the concentration of NaHCO3 and Na2CO3 was 0.2%.With the salt concentration increases,the K+/Na+in different parts were all decreased,and the accumulation of Na+ was increased.The accumulation and distribution of K+and K+/Na+in different parts were shown as aboveground>root,while Na+was root>stem>leaves.Under salt stress,the transport selectivity coefficient(ST1K,Na)of the root system to the stem sheath was significantly higher than that of the control.6.From correlation analysis,principal component analysis and comprehensive evaluation of membership function.The proline content,soluble sugar content,SOD activity,K+content of leaf stem and root,Na+content of leaf and stem,K+/Na+of stem,Fv/F0 and malondialdehyde content could be used as physiological and biochemical indexes for evaluated salt tolerance of chinochloa frumentacea seedlings under salt-alkali stress.The salt tolerance order of chinochloa frumentacea seedlings was Na2SO4>NaCl>NaHCO3>Na2CO3.7.The improvement effect of on saline-alkali soil was obviously,among them,the improvement effect of 0?20 cm topsoil was greater than that of 0?40 cm topsoil.In the 0?20 cm topsoil,The bulk density was decreased 2.34%?3.65%,the total porosity was increased 3.69%?15.06%,the pH was decreased5.14%?8.25%,the total salt content was decreased 20.70%?29.41%and the alkalinity was decreased 16.79%?24.07%.In the 20?40 cm topsoil,The bulk density was decreased 1.10%?1.17%,the total porosity was increased 3.62%?10.56%,the pH was decreased 0.54%?1.62%,the total salt content was decreased 17.50%-35.56%and the alkalinity was decreased 6.68%?7.61%.In summary,the study has revealed the saline-alkali tolerance characteristics of chinochloa frumentacea and its improvement effect on saline-alkali soil with 2 years biological improvement by laboratory and trial experiments.The results could be provided as a scientific basis and practical guidance for chinochloa frumentacea biological improvement of saline-alkali land.