Salt Tolerance Of Five Gramineous Ornamental Grasses Under NaCl Stress

In this experiment,five species of ornamental grasses,such as Festuca glauca,Cortaderia selloana,Miscanthus sinensis,Pennisetum alopecuroidea L.Spreng,and Nassella tenuissima were used as experimental materials.The NaCl concentrations were CK,0.1%,0.3%,0.5%,0.7%,0.9%,1.1%(NaCl as a percentage of soil dry mass)were subjected to salt stress treatment during seed germination and seedling growth period,and the indicators related to seed germination and physiological and biochemical correlation of seedlings were determined.Variance analysis,principal component analysis and membership function calculation were used to identify the salt tolerance of five ornamental grass materials,which provided a theoretical basis for salt tolerance evaluation and application of saline-alkali soil.Research shows:(1)0.1%NaCl stress promoted Festuca glauca germination rate,Nassella tenuissima germination rate and germination potential,and low salt treatment promoted Nassella tenuissima germination rate and germination potential significantly(P<0.05);after that,with the increasing concentration of salt treatment,the germination rate and germination potential of both materials showed inhibition and strengthening effect.The germination rate and germination potential of Cortaderia selloana,Miscanthus sinensis and Pennisetum alopecuroidea L.Spreng were inhibited by NaCl treatment at various concentrations,and the germination rate of Cortaderia selloana was 0 under 1.1% NaCl treatment.Although the effects of salt stress on seed germination were uneven,the germination and radicle growth of the five tested materials were inhibited by salt stress,and there was a very significant negative correlation between salt stress and the concentration of salt treatment.(2)The relative conductivity of five ornamental grasses increased with the increase of salt concentration,but the effect of low salt treatment(0.1%、0.3% NaCl)on the relative conductivity of five ornamental grasses was not significant(P>0.05).Except for Cortaderia selloana,the accumulation of malondialdehyde(MDA)in Festuca glauca,Miscanthus sinensis,Pennisetum alopecuroidea L.Spreng and Nassella tenuissima materials was similar to that in conductivity,and increased with the increase of salt concentration,while the content of malondialdehyde(MDA)in Cortaderia selloana decreased first and then increased.(3)The content of chlorophyll(chlorophyll a,chlorophyll b and total chlorophyll)of Festuca glauca,Pennisetum alopecuroidea L.Spreng and Nassella tenuissima decreased with the increase of salt concentration,and all decreased to the lowest level at 1.1% NaCl concentration.The content of chlorophyll(chlorophyll a,chlorophyll b and total chlorophyll)of Cortaderia selloana and Miscanthus sinensis increased first and then decreased with the increase of salt concentration,and the total chlorophyll reached the highest level at 0.7% and 0.1% salt concentration,respectively.(4)Under various salt stress conditions,except for the linear accumulation of soluble protein content in Pennisetum alopecuroidea L.Spreng,the soluble sugar and soluble protein content of five ornamental grasses increased first and then decreased with the increase of salt concentration.The salt concentration corresponding to the peak value of soluble sugar and soluble protein in different materials was different,but the content of soluble sugar and soluble protein basically decreased to the lowest at 1.1% NaCl concentration.There was a positive correlation between the content of free proline and the concentration of salt,and the cumulative change rate of Miscanthus sinensis was the highest.(5)The activities of SOD,POD,CAT,APX and GR of the five tested materials increased first and then decreased with the increase of salt concentration.There were significant differences among different salt concentration and different varieties.As far as the range of salt concentration corresponding to the increase of enzyme activity is concerned,the range of salt concentration corresponding to the increase of five enzyme activities in Festuca glauca cells is the widest.As far as the final inactivation rate of enzyme activity is concerned,the final inactivation rate of SOD in Pennisetum alopecuroidea L.Spreng is the lowest;that of POD,CAT and APX in Festuca glauca is the lowest;and that of GR in Miscanthus sinensis is the lowest.(6)Subordinate function method was applied to evaluate the salt tolerance of five ornamental grasses at seed germination stage,the order of salt tolerance was Festuca glauca > Miscanthus sinensis > Pennisetum alopecuroidea L.Spreng > Cortaderia selloana > Nassella tenuissima from big to small in this stage;While principal component analysis method was applied to evaluate the salt tolerance of five ornamental grasses at seedling growth stage,it was concluded that APX activity,soluble sugar content,chlorophyll content,GR activity and SOD activity could be used as ornamental test.The primary evaluation index of salt tolerance of grass seedlings at growth stage was Miscanthus sinensis > Festuca glauca > Nassella tenuissima > Pennisetum alopecuroidea L.Spreng > Cortaderia selloana,and the comprehensive evaluation of salt tolerance at two growth stages was Miscanthus sinensis > Festuca glauca > Pennisetum alopecuroidea L.Spreng > Cortaderia selloana > Nassella tenuissima.