Effects of Different Position and Ages of Twigs on Cutting of Ginkgo biloba and Its Relationship with Non-structural Carbohydrates

Objective To explore the effects of twig ages on the formation of the adventitious roots from the upper and lower branches in the crowns of Ginkgo biloba, and discuss the relationship between rooting and non-structural carbohydrates (NSC) in the corresponding leaves and stems.

Method Experimental materials with the cutting of one-, two-, and three-year-old twigs were investigated from the upper and the lower parts of the crown, and the NSC contents were analyzed by the HLPC in the leaves and stems of the corresponding positions. All cuttings were treated with 0 and 500 mg·L^-1 IBA under natural light and spraying management.

Result The process of the adventitious root formation includes four stages:callus formation (0-4 weeks), callus expansion (4-6 weeks), initiation of adventitious root (6-8 weeks) and root elongation (after 8 weeks). No significant difference was observed in the rooting of cutting between the twigs from the upper and the lower branches of crowns, while it was considerably inhibited by the ages of twigs. The NSC analysis showed that the contents of polysaccharides and total sugars in the leaves from the lower crown were higher than the upper one, but all the NSC components tested showed no significant differences between the twigs from these two parts. However, the NSF contents had no significant changes in the corresponding leaves, whereas they decreased significantly in the corresponding stem fragments with the increasing ages of twigs, including glucose, fructose, polysaccharides, total sugars and starch, which showed the similar trends with the rooting changes. Besides, the treatment of 500 mg·L^-1 IBA didn't improve the rooting rate compared to the control, and this needed to be further optimized.

Conclusion The position of the upper and lower branches has no significant effect on the formation of adventitious roots in the crowns of G. biloba. The age of untreated twigs was negatively correlated with rooting, but stem NSC content was positively correlated with rooting; the induced callus rooting is the main type for the cutting of G. biloba. This result will provide the references for the future study of cutting process and its mechanism in G. biloba.