| Thirty native and introduced tree species were treated with 0.5 times (0.197%), 1.0 times (0.394%), 2.0 times (0.788%), 2.5 times (0.985%) salt solution, which simulated salt concentration of alkaline patch in Daqing. Proline, peroxidase(POD), superoxide dismutase(SOD), cell membrane permeability, photosynthesis rate were analyzed after 20 and 30 salt treatment. The results showed ascension and descent ranges of different trees were different. Five tree species, namely Elaeagnus angustifolia, Lycium brabarum L., Caragana microphylla Lam., Ulmus pumila L. and Sorbus pohuashanensis (Hance) Hedl.were primarily proved to have stronger salt-resistance ability. At the same time, Elaeagnus angustifolia, Caragana microphylla Lam, and Sorbus pohuashanensis (Hance) Hedl.were also used to study their tissue culture propagation.1. Effects of salt treatment on related biophysical-chemical indexUnder salt treatment, the content of free praline and SOD activity increased with the concentration of salt;POD activity was descended firstly, and ascended then descended with increasing salt concentration;Relative conductance responded to salt treatment appeared the same trend with free praline and SOD activity, and under 2.5 times salt concentration on 20d, relative conductance was significantly higher than CK;Photosynthetic rate of tree species responded to 0.5 times , 1.0 times salt concentration were different. However, photosynthetic rate was distinctly lower than that of CKunder 2.5 times salt concentration.2. Selecting Salt-tolerance treesIntegrated rating law was used to select salt-tolerance trees from the above tested biophysical-chemical index. The trees' salt-tolerance was Elaeagnus angustifolia>Lycium brabarum L.> Caragana microphylla Lam.> Ulmus pumila L.> Sorbus pohuashanensis (Hance) Hedl.3. Study on tissue culture propagation in salt-tolerant treesElaeagnus angustifolia could produce multiple bud clumps in Ms + 6-BA 0.5 mg·L-1. Under MS+6-BA0.5-1.0mg·L-1+NAA0.8mg·L-1, Elaeagnus angustifolia stems could induce a large number of callus shoots. After tube seedlings were soaked by IBA50mg·L-1 forlh, and cultured to media without hormones, the rooting rate is 94%.Stem segments with axillary buds in Sorbus pohuashanensis (Hance) Hedl.were chosen as explants to study tissue culture propagation technology. The results showed that the best basic medium was MS;axillary buds were induced successfully on MS basal media supplemented with 6-BA2.5mg·L-1and 2.4-D0.5mg·L-1;the optimum medium for bud proliferation was MS+6-BA(1.6-2.1)mg·L-1 + NAA (0.14-0.23) mg·L-1;the shoots grew strongly on MS+6-BA1.2mg·L-1+IBA0.2mg·L-1;and l/2MS+IBA0.3mg·L-1 was the best medium for shootrooting, the rooting rate was 90.20%, and the average root number of 5.96;plantlets survival rate reached 95.55% when transplanted on the mixture (soil3: peat moss2: sandl).Stem segments of Caragana microphylla Lam. were used to optimize the tissue culture condition. The results showed that MS+6-BA0.5mg-L"1+IAA0.01mg-L'1 was the optimum medium for inducing bud, l/2MS+IAA0.5mg-L"' best fitting for rooting.
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