Effects Of Salt Stress On The Growth And Physiological Properties Of Pteroceltis. Tartarinowii. Maxim. Seedlings

This paper deals with the growth and physiological properties of P. tartarinowii.under Nacl stress of different concentrations by the way of hydroponics in a greenhouse.Six different treatments.were.performed:control(0g/l.Nacl),Sl(lg/l.Nacl),S2(1.5g/l.Nacl),S3(2g/l.Nacl),S4(2. 5g/l Nacl)and S5(3g/l Nacl).These reagents were prepared with Hoagland nutrient solution.lt is the purpose of this study to ascertain the concentration of Nacl under which the growth of seedlings of P. tartarinowii. are significently inhibited and the physiological metabolism in the seedlings of P. tartarinowii.is seriously disturbed and to provide scientific basis for expanding reasonably the planting area of P. tartarinowii.plantation. According to the indexes determined in the study ,the conclusions drawn are as follows:1 In general,with increasing salinity the percentage germination of the seeds,the germination power of the seeds,the height incrementation of the seedlings,the caliper incrementation,the biomass incrementation and the survival percentage of the seedlings decreased 2.The content of chlorophyll in the leaves decreased as stress time progressed,and it alsodecreased with increasing salinity.3.The membrane permeability and the proline content of the leaves remined almost unchanged at the initial stage of salt stress,but both of them remarkably increased with increasing salinity in the later stage of salt stress.4.Leaf water potential was affected only in the early days of salt stress,namely,increasing Nacl concentrations generally decreased leaf water potential,but soon the leaf water potential of Nacl treatments returned to the level which was similar to that of control. 5 The nitrate reductase activity in the leaves of control,Sl,S2 and S3 generally increased at first ,then decreased as stress time progressed before 18th,september,while both the nitrate reductase activity in the leaves of S4 and that of S5 versus stress time curves had the two-bell shape.The nitrate reductase activity in the leaves of control,Sl,S2 and S3 increased again ,while that of s4 decreased on 4th ,Octomber. 6.At the initial stage of salt stress root activity generally increased at first,but decreased laterwith increasing salinity,but it decreased generally with increasing salinity since then. 7.1n the early days of salt stress the activity of superoxide dismutase(SOD) in the leaves generally increased at first ,then decreased with increasing salinity,since then there was a slight difference in the SOD activity in different treatments.It generally increased at first,but decreased later again with increasing salinity after 5th,September. In general,the activity of peroxidase(POD) increased at first,but decreased later with increasing saliniry.The activity of catalase(CAT) in the leaves varied with treatments as well as the time of salt stress.The activity of CAT in the leaves of control remained stable as time progressed. The activity of CAT in the leaves of S1,S2 and S5 increased at first,but decreased later as stress timeprogressed. The activity of CAT in the leaves of S3 versus salt stress time curve had the two bell shape.The activity of CAT in the leaves of S4 did not decrease until the later stage of salt stress.8.The MDA contents in the leaves of control,Sl,S2 and S3 increased at first,but decreased later,whereas those of S4 and S5 increased at first,then decreased and increased again at last as stress time progressed.9.1n general,with increasing salinity the net photosynthetic rate ,the transpiration rate and the stomatal conductance gradually decreased,whereas the intercellular COa concentrations in the leaves gradually increased.10. In general,with increasing salinity the concentrations of total K in the leaves increased at first,but decreased later, whereas both the concentrations of total K in the stems and that in the root decreased.The concentration of total Na in the leaves generally increased at first,but decreased later with increasing salinity,so did those in the stems and rootThere were trifling difference in the co...