Abstract: The induction of polyploidy has many advantages such as the huge organ, stronger resistance and increase of metabolite, and it is often used for breeding research of medicinal plant. In this study, the peppermint stem containing bud was induced by colchicines in order to obtain the chromosome doubling variant plants. The peppermint stems were induced by colchicines separately with different concentrations(such as 50、100、150、200 mg/L) and different processing time, and the optimum concentration and processing time were screened out by comprehensive consideration of the mortality rate of stem, the induction and growth of regenerated shoot, and the rate of variant plants. The optimum combination is 150 mg/L colchicines for 48 h. The growth, leaf morphology, the size and density of stomata, and the chromosomes number of the variant plants were observed. The peppermints with chromosome number doubled were successfully obtained, which laid the foundation for the breeding and selection of peppermint.

Key words: colchicines, chromosome doubling, regenerated shoot, peppermint