Study on salt stress of 3 ornamental trees during germination period.

With the controlled experiment and the grads of salt stress,the characters of physiological biochemistry of 3 ornamental trees Periploca sepium,Fraxinus velutina,Grewia biloba var.parviflora were studied during their seeds germination.And the growth,the activity of defense enzymes,the lipid peroxidation and the critical salt concentration of three species had been measured systematically,and evaluated by the fuzzy subordination methods.The results showed that with the increase of salt concentration,the seed germination rate,germination index,radicle growth rate,hypocotyl growth rate,vigor index and the relative water content of the three species reduced gradually.Under salt stress,this phenomenon of P.sepiumF.velutinaG.biloba var.parviflora during the germination time.The critical salt concentrations for every salt tolerance index were P.sepiumF.velutinaG.biloba var.parviflora.With the increase of salt concentration,superoxide dismutase(SOD) activities of P.sepium and F.velutina decreased at first,increased at end;Peroxidase(POD) activities increased at first,and decreased at end;and the contents of MDA kept the lower level during stress.But SOD activities of G.biloba var.parviflora increased at first,and decreased at end;POD activities declined continually;and the content of MDA had more variation range.The salt resistances of the three species decreased in the order of P.sepiumF.velutinaG.biloba var.parviflora by the evaluated of the fuzzy subordination methods.The seeds germination and growth of the three species were impacted by salt stress,P.sepium had stronger NaCl tolerant ability than F.velutina had and the NaCl tolerance of F.velutina was stronger than that of G.biloba var.parviflora.