Abstract

In this study, the physiological and biochemical responses of a halophyte Kalidium foliatum to salinity were studied. In order to reflect salt-tolerance in K. foliatum and to analyze the physiological and biochemical mechanism for its salt tolerance, salinity threshold and biochemical parameters were studied. A halophyte, Suaeda glauca, which has strong salt resistance, was selected as a control and the changes in soluble sugar, malondialdehyde (MDA), proline, Na⁺ and K⁺, Na⁺/K⁺ratio, and activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were investigated. Four months old K. foliatum seedlings were subjected to 0, 0.15, 0.30, 0.45, 0.60, 0.75 and 0.90 M NaCl for 7 days. Salinity increased Na⁺ content in K. foliatum, while Na⁺/K⁺ ratio did not quite change. Salinity also increased Na⁺ content in S. glauca; however, Na⁺/K⁺ratio changed with the increase of NaCl concentration. With the increase of NaClconcentration, MDA content in K. foliatum decreased, however, MDA content in S. glauca increased and this was related to enhanced activities of SOD, CAT and APX enzymes in K. foliatum. Content of soluble sugar and proline were lower in K. foliatum than in S. glauca. All these results suggest that there are different salt resistant metabolisms between K. foliatum and S. glauca, and salt treatments and salinity tolerance of K. foliatum might be closed related to increased capacity of antioxidative system to scavenge reactive oxygen species, stable absorption of K⁺and maintain Na⁺/K⁺ ratio.

Key words: Kalidium foliatum, Suaeda glauca, salinity stress, halophyte, salinitythreshold, physiological adaptations.