Abstract: 【Objective】 To screen the optimal hormone treatment method for polychromatic crape myrtle cuttings for improving the production efficiency of polychromatic crape myrtle.【Methods】 The young branches of polychromatic crape myrtle were used as cuttings to analyze rooting rate and root effect index under different hormone types,hormone concentrations,treatment time,treatment part,and to detect its endogenous hormones and nutrients changes during the rooting process of cuttings under the optimal treatment and water soaking.【Results】 The hormone treatment could improve polychromatic crape myrtle rooting significantly. Hormone types and hormone concentration both had a highly significant effect on the rooting rate and root effect index（P<0.05）,and treatment time could affect significantly the rooting rate only （P<0.05）,but reatment part had no significant difference （P>0.05）. The comprehensive influence of four factors was hormone types>hormone concentrations>treatment time>treatment part. The optimal treatment was 400 mg/L IBA to treat the lower 1/3 part of the branches for 5 min. The detection of endogenous hormones and nutrients during the rooting process of cuttings that were optimally treated and soaked in water showed that hormone could increase the content of IAA,soluble sugar content and soluble protein content in the critical period of rooting,meanwhile reduce the ABA and ZR content,and promote differentiation of root primordia and elongation of adventitious roots.【Conclusion】 The cutting effect of 400 mg/L IBA on the lower 1/3 part of branches for 5 min was better,and the higher rooting rate and root effect index of polychromatic crape myrtle could be obtained.

Key words: Polychromatic crape myrtle, Hormone treatment, Rooting rate, Root effect index, Endogenous hormone, Nutrient