Response and enrichment ability of perennial ryegrass under lead and cadmium stresses

The object of this study was to evaluate the effect of lead and cadmium stresses on growth and development of perennial ryegrass and to better understand the potential of perennial ryegrass for phytore mediation of Pb and Cd contaminated soils,and provide technical information for soil remediation planning.In a pot experiment,Pb was spiked at 0,300,500,1000,1500 mg/kg,and Cd was spiked at,0,0.3,3,10,50,100mg/kg.Further,Pb and Cd treatments were combined as follows:Pb_0Cd_0(CK),Pb_(300)Cd0.3,Pb_(500)Cd_(0.3),Pb_(1000)Cd_(0.3),Pb_(1500)Cd_(0.3),Pb_(300)Cd_(10),Pb_(500)Cd_(10),Pb_(1000)Cd_(10),Pb_(1500)Cd_(10).Measurements made included germination vigor,an establishment rate index,chlorophyll content,photosynthetic rate,transpiration,water use efficiencies of seedlings,as well as photosynthetically active radiation,and light use efficiency.The Pb and Cd contents of root,stem and leaf were determined in the seedlings.Compared to CK,there was no significant difference in germination at lower concentrations(300,500mg/kg)of Pb stress,but there was an adverse effect at higher concentrations(1000,and 1500 mg/kg).Lower concentrations of Cd stress promoted seed germination,but where Cd concentration was more than 10mg/kg,there was inhibition of seed germination.With increase in Pb concentration,chlorophyll content also increased,but Cd stress the opposite tendency was noted.Photosynthetic rate decreased at lower concentrations and then increased at higher concentration under Pb or Cd single stress.Photosynthetic rate peaked when Pb concentration was 1000mg/kg or Cd concentration was 10mg/kg.The enrichment coefficient decreased with increase in concentration of the metals Pb or Cd.The Pb and Cd combinations showed stronger inhibitory effects on seed germination than single metal exposure stress.The enrichment ability of perennial ryegrass to Pb and/or Cd was rootstemleaf.The enrichment coefficient of Cd was greater than that of Pb.Perennial ryegrass showed a better remediative effect on lightly polluted soils.