| The aim of this experiment was to study the protective effect of 5-ALA on Poa pratensis L.when Poa pratensis was under salt,drought and Cd stress.And determined which concentration of 5-ALA was the best.In this study,Poa pratensis L.was used as the test material.Studied physiological,photosynthetic characteristics and seed germination and plant growth of Poa pratensis L.after treated with three kinds of obiotic stress.1.This trial was aimed to investigate the effects of different concentrations of 5-aminolevulinic acid(5-ALA)on seed germination and seedling growth of Poa pratensis under Cd stress,salt stress and drought stress with germination test.Poa pretensis ‘Midnight' was used as the material,and five different concentrations of 5-ALA(0,5,25,50,100 mg/L)were applied to the treatment of Cd(2 mg/L),Na Cl(100 mmol/L)and PEG(15%),and germination energy,germination rate,soluble protein and other indexes were analyzed.The results showed that the germination energy,germination rates,bud length,root length were increased with the lower concentrations(5,25 mg/L)of 5-ALA.When the concentration was more than 25 mg/L,the protection of 5-ALA on the seedlings was decreased gradually with the increase of the concentration,and even enhanced damage.This study shows that the best concentration was 25 mg/L after a general comparison among four concentrations of 5-ALA.Under this concentration,germination energy and germination rates were increased by 21% and 33.67% respectively compared with the control under Cd stress.Under salt stress,germination energy and germination rates were increased by 22.67% and 23.67% respectively,and the two indexes were increased by 15.33% and 10.67% respectively under drought stress.In addition,soluble protein content was significantly increased by 6.5 ?g/g,3.8?g/g when the seedling was under salt or drought stress(P<0.05).2.Applied three kinds of abiotic stress and lasted three weeks after the Poa pratensis growth three weeks.Every week sprayed 30 ml different concentrations of 5-ALA on leaves during stress treatment period.Then measured photosynthesis and physiological indexes.The results showed that the effects of spraying different concentrations of 5-ALA on aboveground biomass were greater than that of belowground biomass.Concentrations of 25 and 50 mg/L were beter in this test,and 25 mg/L was best.In the test,in addition to the content of MDA under drought stress did not decline after used 5-ALA.The contents of MDA and Pro showed ‘U' relation with the concentrations of 5-ALA in the other treatment groups.This means that the appropriate concentrations of 5-ALA can effectively reduce the damage caused by stress.The contents of SOD,POD and CAT were significantly higher than those of control after spraying 25 mg/L of 5-ALA(P<0.05),and the effects of the other three concentrations were not significant(P>0.05).The photosynthetic efficiency of Poa pratensis L.was significantly increased under three kinds of stress after adding 25 mg/L of 5-ALA(P<0.05),and this concentration of 5-ALA was the best among the four concentrations.Transpiration rate increased first and then decreased with the increased of 5-ALA concentration.Only under the Cd stress,25 mg/L and 50 mg/L of 5-ALA can significantly increased the transpiration rate.The application of 5-ALA did not improved the transpiration rate when plants under other stress.In conclusion,this study proved that 25 mg/L of 5-ALA had the best protective effect on Poa pratensis L.under stress. |
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