Analysis Of Salt-tolerance In Suaeda Physophora Seedlings Under NaCl Solution

Suaeda physophora,which is distributed mainly in inland desert of China (the North of Xinjiang autonomous region) and the Central Asia, is a halophyte with succulent leaf. It can provide forage for livestock, and it plays an important role in improving salinilizing soil and fighting back wind erosion. The seedlings of Suaeda physophora in 5d, 10d, 15d, and 30d were treated with the concentration of 100, 200, 400, and 500mmol/L NaCl solutions. The growth, contents of organic solutes and inorganic ions were measured and responses of seedlings in different age to NaCl stress were investigated. The results were as following:The growths of seedlings for Suaeda physophora were promoted in the low concentration of NaCl solution and obviously inhibitted in the higher salt concentration. The optimum was 200mmol/L NaCl solution irrespective of the concentration treatment or the seedling's age. However, seedlings at the earlier stages seemed more sensitive to NaCl stress than those at the latter stages.Suaeda physophora accumulated Na+ , Cl- in above-ground mainly. Both ions in organs distributed as leaf>stem>root and their contents increased remarkably as NaCl increasing. However, the ratio of K+/Na+ decreased significantly as salt concentration increased. It was observed that the older seedlings accumulated more ions.Under NaCl treatment, the contents of proline, soluble sugar in stems and leaves of Suaeda physophora increased. Proline in the seedlings at 30d existed significant differences with the control under 100, 200, 400 and 500mmol/L NaCl solutions, and were 1.54, 1.71, 1.77, and 2.15 times more than that under the control, respectively. Suaeda physophora accumulated more proline and soluble sugar to maintain the balance of osmotic,and they resisted the salt injury through osmotic adjustment.The contents of Chla, Chlb, Chl and Chla/Chlb decreased as the NaCl concentration increased. Compared with Chlb, however, the content of Chla had a more significant decline under NaCl and Cha seemed more sensitive to salinity.As a result, the growth of seedlings for Suaeda physophora were inhibitted as concentration of NaCl increased due to the decline of chlorophyll contents in leaves. The falls of growth in seedlings, however, were dependent on the age of seedlings, and the younger seedlings were more sensitive to salinity. NaCl promoted the accumulation of Na+ , Cl- , and proline, soluble sugar in stems and leaves of Suaeda physophora, and the contents of these ions and solutes in the older seedlings increased more than those in the younger under the higher salt concentration. This suggested that the accumulation of inorganic and organic solutes might play an important part in alleviating hurt from salinity and keeping growth in seedlings of Suaeda physophora.