Abstract:In order to disclose the salt tolerant mechanisms of Dendranthema, the absorption, transportation and organ-compartmentalized distribution of K+, Na+ and Cl- under different concentrations of NaCl stress were compared in seedlings of two Dendranthema species via hydroponics method. Under NaCl stress, both species showed decrease in ratio of newly developed leaf area while increase in ratio of injured leaf area per plant, and relative electricity conductivity in leaves increased too. Dendranthema crassum was lesser affected by NaCl stress than D. ornatum did. The Na+ and Cl- contents increased with the increase of NaCl concentration, and accumulations of Na+ and Cl- were more in organs above the ground than those in roots in both species. Similarly, K+ content elevated with increase of NaCl concentration in newly developed leaves and stem. Mature leaves seemed to be the main storage organ for Na+ and Cl-. Compared with salt tolerant D. crassum, the salt sensitive D. ornatum showed more Na+ and Cl- accumulation in all organs, and its growth was more susceptible to the contents of accumulated Na+ and Cl-. The ratios of K+/Na+ in all organs except root of D. crassum under severe NaCl stress were higher than those in corresponding organs of D. ornatum. D. crassum had a higher transportation selectivity of K+/Na+ (designated as SK,Na) from root to stem, whereas a lower SK,Na from stem to middle mature leaves under same salt stress. However a higher SK,Na from stem to upper newly developed leaves was observed under high NaCl stress. All these data indicated that D. crassum could maintain a better K+/Na+ ratio rather than to accumulate Cl- and Na+, constrain Na+ in the root, and keep lower SK，Na from stem to upper newly developed leaves, all of which are good explanations for its salt tolerance. Higher SK，Na from stem to middle mature leaves probably represented a kind of accommodation to salt stress of D. crassum. Based on multiple-linear regression analysis, the growth of D. ornatum was affected more evidently by Cl- than by Na+.