| Four species (Elymus sibiricus Linn., Elymus nutans Griseb., Caragana korshinskii Kom. and Zygophyllum xanthoxylon Maxim.) which are adaptive to the growing condition of the Xining Basin and the surrounding areas have been taken as the test species. Salt stress test with Na2SO4 solution whose concentration gradients are 0, 30, 60, 90 and 120 mmol/L have been applied to the four species. By measuring the basal diameter (rhizome diameter), plant height and dry weight and six ion (Na+, K+, Ca2+, Mg2+, Cl- and SO42-) content in above-ground part and under-ground part for the four species, salt–tolerance property of the four species have been investigated. The result exhibits under salt solution with some certain concentration, growth of the four species has been depressed to some extent, and basal diameter (rhizome diameter), plant height and dry weight decline gradually, and the depressive effect on above-ground part is relatively larger than that of under-ground part. Solution with concentration larger than 30 mmol/L has a certain promotion effect on the growth of Z. xanthoxylon. With the solution concentration soaring, content of Na+ and SO42- in both the above and underground parts of the four species increase significantly, whereas the content of the other ions (K+, Ca2+, Mg2+ and Cl-) exhibit declining trend. Sodium content in underground parts are 1.09 times and 1.24 times larger than those in above-ground parts of C. korshinskii and E. nutans. Yet for E. sibiricus and Z. xanthoxylon, the counterparts are 1.21 times and 1.75 times larger. In salt stress environment, the ion selection transportation coefficients for four species decline with solution concentration increasing. The ion content ratio of K+ to Na+, Ca2+ to Na+, Mg2+ to Na+, (K++Ca2++Mg2+) to Na+ decline. And ion content ratio of K+ to Na+ for above-ground parts of C. korshinskii is relatively larger, increasing from 0.73 to 9.70, followed by Z. xanthoxylon and E. nutans, increasing from 0.46 and 0.45 to 8.35 and 7.57 respectively. Ion content ratio of K+ to Na+ for above-ground parts of E. sibiricus is relatively less, increasing from 0.25 to 6.12, which means the salt tolerance capacities for the four species from strong to weak are C. korshinskii, Z. xanthoxylon, E. nutans and E. sibiris. The results have theoretically instructive significance in effectively implementing measurements in salinized land reclamation by vegetation in the Xining Basin and the surround regions. |
