Abstract: In order to understand the response of endogenous hormones and adventitious root development of Salix dunnii leaf-bearing cuttings after incubation under red light conditions, continuous tissue sectioning technique was used to observe the process of adventitious root development, and the contents of four endogenous hormones were measured by enzyme-linked immunoassay (ELISA). The results showed that Salix dunnii adventitious roots originated from the cortex were belonged to the induced root primordium. With the appearance of expansion dots in the cortex, the IAA content in the cortex increased significantly during the formation of adventitious root. With the construction of adventitious roots, the IAA content in the cortex of the spike decreased considerably. The ABA content of the cortex of the spike was the highest, the BR content was lower, and the GA content was the least. In contrast, the low concentration of BR induced the formation of lateral roots, and a small amount of GA was beneficial to the induction of adventitious root differentiation at the base of the spike. The expression of Salix dunnii bHLH gene was analyzed to further understand the mechanism of the endogenous hormone BR on the rooting of Salix dunnii cuttings. Accordingly, the rooting of Salix dunnii leaf-bearing cuttings was a complex developmental process regulated by different endogenous hormones.

Key words: Salix dunnii, cutting, paraffin section, adventitious root, endogenous hormones