Abstract: The direct and indirect induction of organ differentiation, callus formation and plantlet regeneration from the leaf and stem explants of the hybrid Populus langfangensis 3 (P. deltoides (“Shan Hai Guan”)×((P. simonii × pyramidalys)₁₂×Ulmus pumila) were investigated in-vitro on Murashige and Skoog (MS) medium supplemented with various concentrations of benzylaminopurine (BA), indole-3-butyric acid (IBA), 1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D). The petiole and leaf explant was easier for direct shoot regeneration along the veins at cutting sites. Direct shooting efficiency was related to both BA concentration and BA/IBA ratio. Efficient and rapid shooting from the leaf and stem explants was achieved on MS medium containing 1~2 mg·L^-1 BA and 0.5 mg·L^-1 IBA. Maximum shooting frequency reached 90%. 2,4-D promoted the callus induction of P. langfangensis 3. The shooting based on callus was obtained on MS medium supplemented with 0.3~0.5 mg·L^-1 BA and 0.02 mg·L^-1 IBA or NAA and the corresponding shooting frequency was 76%. Rooting based on callus succeeded on 0.1 mg·L^-1 BA and 0.2~0.5 mg·L^-1 IBA, yielding rooting frequency 67%. These regeneration conditions could further be used for micropropagation and transformation of P. langfangensis 3.

Key words: Populus langfangensis 3, shooting, rooting, regeneration, callus formation