Studies On Effects And Salt-tolerance Mechanism Of Several Planting Species Under Salt Stress

The growth and physiological and biochemical performance of seven tree species under salt stress were studied by control salt content in pot culture. The effects, the salt-endurance mechanism and salt tolerance ability under salt stress of seven trees species were studied primarily. The main results were as follows:The salt tolerance ability of the seven tree species was: Robinia pseudoacacia L . ,Taxodium mucronatum>Cryptomeria japonica,Toona sinensis (A.Juss.) Roem,Catalpa bungei C. A. Mey.> Quercus rubra L.,Fraxinus griffithi .The relative growth increment of height and diameter were restrained by salt stress. The photosynthetic parameters of the five broadleaf trees were very sensitive to salt stress. The stress caused the stomas closed. The net photosynthesis and transpiration rate were also decreased distinctively, but the Ci was raised. The Fv/Fm,Fs,Fv'/Fm',ETR andФPSâ…¡of the five broadleaf trees were all decreased under the salt stress. Salt stress leaded to higher membrane permeability and the higher content of malondehyde, and the protected action of SOD was not obvious. The RWD and the contents of proline of seven tree species were increased according to the increasing of salt concentration and stress time. The contents of Na⁺ in leaves and roots, K⁺,Mg²⁺ and Ca²⁺in leaves were all increased.With the increasing of salt concentration, the changes of physiological indexes of Quercus rubra L. and Fraxinus griffithii are more obvious than Robinia pseudoacacia L.and Taxodium mucronatum.The different tree species had the different reaction and salt-endurance mechanism. The increasing content of Na+ in leaves of Robinia pseudoacacia L. was less than in roots, which showed that the Na⁺ in root was transfered little into the upside. Its salt-endurance mechanism was avoiding the salt to be absorbed. Also, it accumulated abundant proline to balance the osmoregulation and the RWD. Taxodium mucronatum had much more Na+ contention in root than other trees under control treatment. It could restrain the absorbtion of Na⁺ in roots to adapt to the salt stress. Cryptomeria japonica,Toona sinensis (A.Juss.) Roem and Catalpa bungei C. A. Mey could keep the membrane structure and reduce the salt damage by decomposing the soluble protein into the proline. Fraxinus griffithii and Quercus rubra L. were extraordinarily sensitive to salt stress. Those salt tolerance were worse.The salt tolerance abilities were valued by coordinate integrative assessment. The sequence was: Taxodium mucronatum>Robinia pseudoacacia L.> Cryptomeria japonica>Toona sinensis (A.Juss.) Roem>Catalpa bungei C. A. Mey.> Quercus rubra L. >Fraxinus griffithii .The seven tree species were classified into three sorts according to salt-tolerance abilities by the clustering analytical method. Type 1 (Taxodium mucronatum and Robinia pseudoacacia L.) were resistant to salt-stress. Type 2 (Cryptomeria japonica,Toona sinensis (A.Juss.) Roem and Catalpa bungei C. A. Mey.) were moderately tolerant to salt-stress. Type 3 (Fraxinus griffithii and Quercus rubra L. ) were intolerant to salt-stress.