关键词: 侧柏古树, 扦插, 不定根, 内源激素, 非结构碳水化合物, 解剖结构

Abstract: [Objective] The cuttings of the seedlings and graftings, derived from old Platycladus orientalis, were used as the experimental material. The differences of endogenous hormones, non-structural carbohydrates, lignification and morphological anatomy in the cuttings were investigated, which aimed to lay a foundation for the acquisition materials and rooting mechanism of the cutting derived from old P. orientalis.[Method] Seedlings were raised from seeds that were collected from 2000-year-old and 5000-year-old P. orientalis, respectively, (known as S5-2000 and S5-5000). Graftings were grafted with scions that were derived from 2000-and 5000-year-old P. orientalis, respectively (known as G2-S3-2000 and G2-S3-5000).One-year-old branches were cut from the above seedlings or graftings, and used for cuttings in this study. Before cuttings, the basal stems of the branches were used to determine IAA, GA3 and ABA by HPLC, soluble sugars and starch by Anthronecolorimetric method, and lignifications by anatomy. The status of adventitious root primordial of the cuttings was observed by the cross-section in four months.[Result] Before cuttage propagation, IAA in the base part of cutting from seedlings was significantly higher than that of the graftings, while GA₃ had no significant differences between these materials. ABA in S5-5000 was higher than that in G2-S3-5000. Soluble sugar and starch, and lignification of xylem had no significant differences in these two kinds of materials. Moreover, no latent root primordial were found in these four kinds of materials, and there was no difference in the degree of lignification of cuttings between seedlings and graftings. After cutting propagation for four months, the rooting rates in S5-2000 and S5-5000 were 10.0% and 8.3%, respectively, whereas no rooting was found in G2-S3-2000 and G2-S3-5000. Anatomical observation demonstrated that the adventitious root primordia, derived from cambium and xylem, could be found in cuttings from seedlings, while nothing was observed in cuttings from graftings.[Conclusion] Grafting old trees of P. orientalis can provide sufficient materials for the study of old tree cuttings, because the first-generation grafting of the old trees retainsits characteristics of difficult rooting. The formation of adventitious roots in P. orientalis belongs to the type of induced root primordia, however the root primordia could not be found in the trees beyond thousands of years. The genetic background of old trees resulted in a low level in endogenous IAA in grafted trees, which affected the induction of root primordia. But the non-structural carbohydrates such as soluble sugar and starch might be not the reason why cutting of old trees is difficult to root.

Key words: old Platycladus orientalis, cutting, adventitious root, endogenous hormones, non-structural carbohydrates, anatomical structure