To investigate the role of AtNHX5 in plant salt resistance,the plant expression vector pROKⅡAtNHX5 was constructed and introduced into Arabidopsis thaliana.RTPCR assay showed that:(1)AtNHX5 was overexpressed in the transgenic lines.(2)Several transgenic homozygous lines and wildtype plants were evaluated for salt stress tolerance,the results suggest that AtNHX5 transgenic plants were more tolerant to high NaCl concentrations during germination and seedling stages when compared with wildtype plants.Under saline conditions,both fresh and dry weights of the transgenics as well as Na⁺ and K⁺ contents were much higher than that of wildtype.To take transgenic plant a14 as an example,the shoot fresh weight,dry weight and K⁺ content were 1.27,1.54 and 1.16 fold,respectively compared with wild types under 200 mmol/L NaCl treatment,which were significantly higher than that in wild types.These results demonstrate that overexpression of AtNHX5 in Arabidopsis promoted the absorbing capacity of K⁺ and enhanced the salt tolerance of plants.