Study On The Effects Of Salt Stress On The Root Activity And The Content Of Na + , K + In Five Tree Species

The potted one-year-old seedlings of five-tree species were tested to study their responses to salt stress. The seedlings were treated with four levels of salt treatments including 0.0%, 0.2%, 0.4% and 0.6% of salt concentrations. When the experiment was conducted for 12,24,36 and 48 days, samples were taken to study the seedling survival rate。The destroyed sample were taken in 36th or 48th day to study the biomass, root activity and the content of Na~+, K~+. Comprehensive analysis has been made for characters in order to reveal the internal mechanisms. The main results are as follows. The seedling survival rate is a key factor for evaluating their salt resistant ability. The salt resistant levels of those tree species in a descend order were as follows, Fraxinus chinensis Roxb., Sapium sebiferum (L.) Roxb.,Hibiscus syriacus L., Cotinus coggygria Scop., Platanus orientalis L..The content of Na~+ was the greatest in the root, the second in the stem and the least in the leaves. The major affected organ by salt stress was leaf in Hibiscus syriacus L., Cotinus coggygria Scop.. The major affected organs in Sapium sebiferum (L.) Roxb were root and stem. The K~+ was selectively transported and the Na~+ was limited in the transportation from root to stem and leaves in Hibiscus syriacus L., and Fraxinus chinensis Roxb..This primarily makes those tree species be more resistant to salt stress. It was noted that that Platanus orientalis L. was exceptional.The Na~+ ion was selectively transports from root to shoot in seedlings of Cotinus coggygria Scop.. However, that of K~+ was limited. Great amount of Na~+ ion was accumulated accordingly, resulting in the injure of cell membrane, the increase of the Na~+ into the cell. This affects the structure and function of enzyme, and so affects the seedlings growth.