The root of Bupleurum scorzonerifolium Willd., which belongs to Bupleurum in Umbelliferae, has been traditionally used in Chinese medicine. Saikosaponin is its functional ingredients. In this paper, the lead acetate precipitation method was used for ultracytochemical localization of saikosaponin in B. scorzonerifolium root. The relationship between structural development and saikosaponin accumulation in the root was observed using transmission electron microscope. The primary and secondary structures of root of B. scorzonerifolium resembled those of the usual dicotyledons. In the primary meristem, saikosaponin was distributed in the dermatogen and periblem, especially, in parenchyma cells of the epidermis, cortex, pericycle, primary phloem and protoxylem. Pericycle and primary phloem are the main storage region. In the secondary structure, saikosaponin was mainly distributed in parenchyma cells of the pericycle and secondary phloem. Cells of the secondary xylem and vascular cambium also contain a small amount of saikosaponin. Dictyosomes might be related to the synthesis of saikosaponin, plasmodesmata participate in the transport of saikosaponin. The saikosaponin content in the primary structure was more than that in the secondary structure, but the total content in the primary structure was lower than that in the secondary structure.%用醋酸铅溶液对狭叶柴胡(Bupleurum scorzonerifolium Willd.)根内的药用成分柴胡皂苷进行细胞化学定位,在透射电镜下探讨不同发育时期根的结构特征与柴胡皂苷积累的关系.结果表明:狭叶柴胡根的初生结构和次生结构类似一般双子叶植物.在根的初生分生组织中表皮原及皮层原均有皂苷的分布.在根的初生结构中,柴胡皂苷分布于表皮、皮层、中柱鞘、初生韧皮部及原生木质部的薄壁组织细胞内,其中中柱鞘和韧皮部是主要的分布部位.在根的次生结构中,柴胡皂苷主要分布于中柱鞘和次生韧皮部薄壁组织细胞内,在次生木质部及形成层中也有少量分布.高尔基体可能与皂苷的合成有关,且胞间连丝参与皂苷的运输.柴胡皂苷在幼嫩结构中的含量高于次生结构,但其总含量低于次生结构.
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