Abstract: The study with sand culture showed that under seawater stress,the plant height,stem diameter,and dry weight of Helianthus annuusL. seedlings decreased significantly.With increasing seawater concentration,the Cl^-content in root,stem and leaf,Mg²⁺ content in stem and leaf,and Na⁺ and Ca²⁺ contents in leaf were increased,but the K⁺,total nitrogen and total phosphorus contents in root,stem and leaf were decreased.Under the stress of 10% and 20% seawater,Na⁺ and Cl^-were mainly accumulated in root and stem,but less in leaf.After treated with seawater,seedlings’leaf had the highest K⁺/Na⁺,while their root had the lowest one.The calculated S_K,Na in root,stem and leaf was always higher than 1.It was speculated that the interception of Na⁺ and Cl^-by Helianthus annuus L. seedlings at low concentration seawater,and the selective absorption of K⁺ over other ions by root and its consequent transportation to stem and leaf under seawater stress were the main causes for the salt tolerance of Helianthus annuusL. seedlings.

Key words: West of northeast China, Sandy desertification region, Vegetation, Classification