Salt-tolerant mechanism of plants had been a hot issue in plant research field.Salt-tolerant mechanisms was rather complicated,different plants formed its own unique characteristics of adaptability in their adaptation to salt environment.Reaumuria trigyna Maxim,derived from Mediterranean Sea and endemic to Alashan-Erdos Desert of China,is an endangered shrubby perennial plant.This experiment aimed to study salt-tolerant mechanisms of Reaumuria trigyna. The main results were as follows:1.Reaumuria trigyna could complete life cycle in the non-saline soil(salt＜0.I%),salinization of the soil(salt at 0.1～0.3%),and in re-saline soil(salt at 0.5～1.0%),has salt glands in the leaves and soft stem.Reaumuria trigyna is an Exo-reorto halophytes.2.Salt glands of Reaumuria trigyna belonged to typical multicellular salt gland.Salt gland originates in specialized epidermal cells,is composed of 8 cells.Among these cells,2 are collecting cells which are similar to the ordinary mesophyll cell with obvious vacuole,surrounding 6 cells are secretory cells which have thick cytoplasm,form 3 rows,2 secretion cells in the most outer layer are big,cells in the middle secretory and secretion cell in the inner layer connecting with 2 collecting cells are small.The collecting cell collects the salinity from the mesophyil cell and ships to the secretory cell,simultaneously may see a thick cuticle besides lower part of the internal cell and the basic unit between a cell's permeating region small part.Reaumuria trigyna decreased transpiration and adapted to salt environment by succulent leaves,sunking stoma and salt glands which removed excessively absorbed ions and reduce the salt concentrations of active tissues.3.The types of icons was same in the soil solutions,plant tissues and excretion from salt gland,but the excreted ions amount from salt gland was obviously different.Among the excreted ions from salt gland,Na~+ and Cl~- was higher,K~+,Mg~(2+) was lower.The changes of salt gland secretion in the day showed decreasing trend which had very significantly or significantly positive correlation with the relative humidity of the atmosphere from morning to night.In addition,the excretion rate was higher during the day and in the morning than during the night and in the afternoon respectively.The above described findings showed that such high selectivity for Na~+,Cl~-in absorption and excretion of Reaumuria trigyna is of high significance to the plant in balancing nutrition in Reaumuria trigyna and adapting to the wild habitat.4.The optimal temperature for germination was 20～25℃.When the temperature was over 25℃,the germination percentages decreased.NaCl at concentration below 100 mM had no effect on seed germination.When NaCl concentration was over 100 mM,the seed germination obviously decreased until 0.After treatment with NaCI solution for 9 days,then transferred in distilled water, recovery germination percentages of seed treated with high concentration of NaCl(200～500 mM) was about 90%.We can improve seed germination rate and uniformity by treating seed with high concentration of NaCl before sowing.5.Reaumuria trigyn was treated with NaCl of different concentrations(0,100,200,300 and 400 mM).A study about its growth in the different conditions showed that the suitable NaCl concentration of Reaumuria trigyna seedlings growth was 200 mM which was higher than 148 mM --- the seed's tolerance of half-lethal salt concentration.These results suggested that the reasons leading to Reaumuria trigyna for the endangered was saline environment which caused seed germination difficulties.6.A study on antioxidative activities and osmotic ability of Reaumuria trigyn with NaCl was conducted and its result demonstrated:(1) Under NaCl stress,the activities of SOD and POD in Reaumuria trigyna all increased significantly,CAT activity had no distinct difference(P＞0.05). Glutathione and O_2 production rate significantly increased,ascorbic acid salt content decreased, increased significantly,while MDA and the relative conductivity appeared to decrease first and then increase as salinity increase.As a whole,these data suggest that the capacity to limit oxidative damage is important for salt tolerance of Reaumuria trigyna;(2) osmotic adjustments of Reaumuria trigyna mainly relied on Na~+ and Cl~-,soluble sugar,free amino acid,proline and soluble protein, rather than relied on organic acids,K~+,Ca~(2+) and Mg~(2+).7.In order to check out whether there exists specific expression in the Reaumuria trigyna treated by 400mM NaCl,mRNA was extracted the total RNA from the leaves of Reaumuria trigyna treated by 400raM NaCl and the control,cDNA fragments were generated by reverse transcription polymerase Chain reaction(RT-PCR).80 differentially displayed fragments were separated on 6% polyacrylamide gel electrophoresis(PAGE),and five of them were confirmed as positive clones by reverse northern blot hybridization.These fragments were then cloned into vectors for sequencing. The cDNA fragment sequences were compared with data in GenBank using basic local alignment search tool(blast).Our preliminary results showed that five eDNA fragments were expression in Reaumuria trigyna treated by 400mM NaCl.The five cDNA fragments were 386,481,495,369 and 371base pairs,respectively.After searching in GenBank,there were no similar sequences reported about these fragments.In conclusion,salt-tolerant mechanism of Reaumuria trigyna can be summarized with the following features:(1) salt gland secretion;(2) stems,leaves structural characteristics adapting to saline environment;(3) physiological adaptation;(4) salt stress-related gene expression.All these study results showed that salt tolerance of Reaumuria trigyna can adapt to the desert and saline environment for the survival by above ways.