[Objective]The research aimed to probe into the mechanism of polyamine enhancing the tolerance of plants to drought stress and provide theoretical basis for application of polyamine in process of maize drought resistance. [Method]With PEG-6000 simulating natural drought,the change in content of soluble protein and relative water content were investigated in seedling leaves of two maize cultivars,Nongda 108 and Yedan 13 under osmotic stress with exogenous Spd treatment. [Result]On the 7th day,leaf relative water content and the content of soluble protein decreased more significantly in leaves of Yedan 13 （drought-sensitive） than in Nongda 108 （drought-tolerant）. Exogenous Spd treatment not only obviously inhibited the decrease of leaf relative water content,but also increased the content of soluble protein. [Conclusion]Exogenous Spd treatment could enhance the tolerance of maize seedlings to osmotic stress,via improving the content of soluble protein in seedling leaves.
