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Objectives:Environmental stresses are most threatening factors for plant productivity.Due to global problem of climate change and arid/semi-arid climatic conditions of Pakistan,salinity is one of the biggest problems for crop productivity and quality.This study was planned to evaluate glutamine synthetase(GS)activity and protein synthesis in response to salinity stress under the influence of combined effect of K+ and NH4+.Methods:A pot study was conducted on maize at salinity level(10 dS m-1)along with 3 levels of K+(0.04,0.08 and 0.12 g kg-1)and 2 levels of NH4 +(0.1 and 0.15 g kg-1).Results: Results showed that all growth parameters regarding shoot and root lengths,fresh and dry weights were reduced under salinity stress.In condition of high NH4 + and low K+ concentration(0.04 g kg-1),more damage was observed while by the increasing K+ concentration up to(0.12 g kg-1)alleviate the negative effects of NH4 + and salinity.Moreover,it partially inhibits the influx of NH4 + and Na+ also stimulates the N-assimilation in plants.Furthermore,at high concentration of K+(0.12 g kg-1),good response was observed in terms of chlorophyll contents,glutamine synthetase activity,protein synthesis,K+/Na+ ratio and K+ concentration in maize plants,while high concentration of K+ also reduced the membrane damage due to salinity and decreased lipid peroxidation.Conclusion:As a conclusion,elevation of K+ supply lead to enhanced plant growth and reduction in the salinity stress and NH4+ toxicity.