Abstract: Simulating chemical properties of the coastal alkaline soil,e.g. ion compostition and concentrations of the ions,in Rudong County,Jiangsu Province,two neutral salts(NaCL and Na₂SO₄) and one alkaline salt (NaHCO₃) were blended into a mixed-salt solution,which was used in this study on its streses on growth and physiological indices of Nandina domestica,Pittosporum tobira,Buxus sinica,Sabina procumbens and Photinia serrulata,by investigating salt injury index,relative dry weight,chlorophyll content,leaf cell membrane osmosis,superoxide dismutase (SOD) and peroxidase (POD) in four treatments,i.e.control (0),3,5 and 8 g•kg^-1.Results show that salt injury index and salt injury rate of the 5 shrubs increased with increasing salt concentration,and the effect varied significantly between the 5 plants,showing an discending order of N.domestica,P.serrulata,B.sinica,S.procumbens and P.tobira.Calculation using the Logistic equation shows that the salt-tolerance threshold of N.domestica,P.serrulata,B.sinica,S.procumbens and P.tobira was 1.74,11.46,6.03,9.63 and 4.75 g•kg^-1,respectively.Moreover,N.domestica was extremely damaged by salt with all the seedlings dead in 5 g•kg^-1 treatment.Thus,its physiological indices were not tested in present study.On the whole,with increasing stress,relative dry weights and chlorophyll contents in leaves of the 4 shrubs were found decreasing in this experiment,while leaf membrane osmosis of the plants increased,and the effect was less significant on P.serrulata and S.procumbens than on the other two.Moreover,compared to the plants in control,S.procumbens and P.tobira in the other 3 treatments were higher in superoxide dismutase activity,whereas P.serrulata and B.sinica was higher only in 3 g•kg^-1 treatment and lower in 5 and 8 g•kg^-1 treaments.With increasing salt concentration,all the plants showed a rising trend in peroxidase and catalase activity,and the effect on catalase activity of P.tobira and peroxidase activity of S.procumbens was most significant,indicating their strong ability to clean oxgen radicals.To sum up,S.procumbens and P.tobira are more tolerant to salts,and can play an important role in greening the coastal area.

Key words: mixture salt, stress, salt tolerance, assessment, physiological index of salt tolerance, enzyme activity