| Leymus chinensis and Elymus dahuricus both belong to the Gramineae and are perennial herbs.They have excellent characteristics,such as the tolerance of saline-alkali,drought,cold,and also have advantages of fast growth rate,strong regeneration ability,multiple harvesting and utilizations.Comparing the tolerance of L.chinensis and E.dahuricus based on heavy metals Cd,Pb,and Zn is very helpful for the application of complex soil environments in gardens,and also lays a reference foundation for remediating heavy metal soil ecological pollution.This original study,L.chinensis and E.dahuricus as research materials,were used to analyze the tolerance to heavy metals Cd,Pb,and Zn through tolerance phenotype experiments,Evans blue staining,chlorophyll content,determination by relative conductivity,determination of total antioxidant capacity,and analysis of glutathione contents.The results of these experiments were as follows:(1)The overall growth of E.dahuricus was better than that of L.chinensis under Cd,Pb and Zn stresses.Low concentration of Zn could promote the growth of E.dahuricus.The seedlings of L.chinensis and E.dahuricus were used to analyze the tolerance under different concentrations of Cd,Pb,and Zn.Under 1 m M-10 m M Cd treatments,the growth trend of L.chinensis was significantly weaker than that of E.dahuricus.However,the relative inhibition rates of plant height and fresh weight were slightly higher than that of E.dahuricus.The biomass of L.chinensis and E.dahuricus was reduced under 1 m M-12 m M Pb treatments,and the relative inhibition rates of plant height and fresh weight also were slightly higher than that of E.dahuricus.Root length,plant height,and fresh weight of E.dahuricus increased at first and decreased later at 1 m M-10 m M Zn stresses.The growth of E.Dahuricus was promoted at low concentration of Zn treatment.The root length,plant height,and fresh weight of L.chinensis decreased with the increase of Zn concentration,and the relative inhibition rates were slightly higher than that of E.dahuricus.(2)L.chinensis and E.dahuricus had their own characteristics in Cd,Pb and Zn transport capacity.The above-ground and below-ground fractions of L.chinensis and E.dahuricus after Cd,Pb and Zn stresses were measured separately.The same heavy metal element was found to be more abundant in the below-ground fraction of L.chinensis and E.dahuricus,with the highest average content of Pb in the below-ground fraction of L.chinensis at 2319.45 mg/kg,and the lowest average content of Cd in the above-ground fraction of E.dahuricus at 39.82 mg/kg.The analysis of translocation coefficient showed that the transport capacity of Cd and Pb of L.chinensis and E.dahuricus was weaker than that of Zn.The translocation coefficient of Cd in L.chinensis was higher than that in E.dahuricus,while the translocation capacity of Pb and Zn was lower than that in E.dahuricus.(3)The damage degree of root cells of L.chinensis under Cd,Pb and Zn stresses was greater than that of E.dahuricus.The roots of L.chinensis and E.dahuricus were stained with Evans blue dye after Cd,Pb,and Zn stresses.The contents of Evans blue staining in the roots was increased with the increase concentrations of Cd,Pb,and Zn.Under 1 m M Cd and 1 m M Pb,the relative growth rate of the dye contents in E.dahuricus was higher than that in L.chinensis.However,the relative growth rate in L.chinensis was significantly higher than that in E.dahuricus in treated with8 m M Cd and 8 m M Pb.The relative growth rate in L.chinensis was always higher than that in E.dahuricus under different concentrations of Zn.(4)The effects of Cd,Pb and Zn on the cell membrane permeability of L.chinensis were greater than that of E.dahuricus.The electricity conductivity(EC)of L.chinensis and E.dahuricus was measured after Cd,Pb and Zn treatments.The EC of L.chinensis and E.dahuricus gradually increased with the increase of concentration,and L.chinensis had higher EC than E.dahuricus under1,8 m M Cd and 1,8 m M Pd.Under 1 m M Zn,the EC of E.dahuricus was higher than that of L.chinensis,and the relative growth rate in L.Chinensis was significantly higher than that in E.dahuricus.In addition,L.chinensis had higher EC than E.dahuricus under 8 m M Zn.(5)The effects of Cd stress,low concentration Pb and high concentration Zn stress on chlorophyll of L.chinensis were greater than that of E.dahuricus.The young leaves of L.chinensis and E.dahuricus were used to extract and calculate the chlorophyll contents after Cd,Pb,and Zn treatments.Under 1 and 8 m M Cd stresses,the relative inhibition rate of chlorophyll contents in L.chinensis was higher than in E.dahuricus.Additionally,the relative inhibition rate in Leymus chinensis was higher than in Elymus dahuricus in treated with 1 m M Pd,but the relative inhibition rate in L.chinensis was similar to that in E.Dahuricus under 8 m M Pb.The relative inhibition rate in E.dahuricus was slightly higher than that of Leymus chinensis at 1 m M Zn,while the relative inhibition rate in L.chinensis was higher than that in E.dahuricus under 8 m M Zn.(6)The ability of E.dahuricus to remove reactive oxygen species(ROS)under Cd,Pb and Zn stresses was stronger than that of L.chinensis.The seedlings of L.chinensis and E.dahuricus were used to test their total antioxidant capacity(T-AOC)under 1 m M Cd,3 m M Pb and 8 m M Zn stresses.The T-AOC of L.chinensis was lower than that of the untreated L.chinensis,while the T-AOC of E.chinensis was higher than that of the untreated E.dahuricus under 1 m M Cd.The T-AOC of E.chinensis was lower than that of the untreated lines under 3 m M Pb and 8 m M Zn.The relative inhibition rate in L.chinensis was higher than that in E.dahuricus under Cd,Pb and Zn.(7)The ability of E.dahuricus to produce heavy-metal-plant chelating peptides under Cd,Pb and Zn stresses was stronger than that of L.chinensis.The GSH content of L.chinensis and E.dahuricus was measured after 1 m M Cd,3 m M Pb and 8 m M Zn,and had both higher GSH contents than the untreated L.chinensis and E.dahuricus.However,the GSH content in E.dahuricus and its relative growth rate were higher than those in L.chinensis under 1 m M Cd,3 m M Pb and 8 m M Zn.In conclusion,E.dahuricus has significantly higher tolerance to heavy metals than L.chinensis under Cd,Pb and Zn stresses.The verification of the heavy metal tolerance in the two kinds of grass species provides certain data support for the ecological restoration in the environment polluted by heavy metals Cd,Pb and Zn in soil,and also gives material reference for the application of herbaceous plants in the soil environment polluted by gardens in the future. |
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