Abstract:

In this paper, cotyledons of Cyclocarya paliurus were used as an experimental material and cultured on the WPM medium to induce adventitious root formation. Effects of different mass concentrations of exogenous ABA and IBA on cotyledon adventitious root formation were studied and relationship between the adventitious root formation and the endogenous hormones changes was investigated. The results showed that adding 0.5～5 mg·L^-1 IBA promoted adventitious root formation on the cotyledon to some degree, and the optimal concentration of IBA was 1.5 mg·L^-1, with which the root-inducing rate, the number of average rooting and the root length all reached to the highest level, with rooting rate reaching to as high as 100%. However, cotyledons with adding 0.01～0.5 mg·L^-1 ABA and the control without hormones had not adventitious root formation. Analyses of dynamics of endogenous hormones indicated that IAA played a key role in adventitious root formation. Initiation of root primordia needed high endogenous IAA, while the relative lower endogenous IAA level was suitable for formation and elongation of adventitious roots. Higher ratios of IAA/ABA and IAA/GA₃ were beneficial to adventitious root formation and could properly reflect the balanced need in endogenous hormones during the rooting process. GA₃ did not appear to be the key factor in adventitious root formation. The research results would provide basis for the study of adventitious root formation and the mechanism in Cyclocarya paliurus.

Key words: Cyclocarya paliurus, cotyledon, adventitious root formation, endogenous hormones