北柴胡根的发育解剖学研究

Anatomical Study of Bupleurum chinense DC.Roots

应用常规石蜡切片方法对北柴胡(B up leurum ch inense DC.)1年生主根的中部和2年生主根的根尖和中部进行了横向与纵向解剖观察,研究根的发育过程,并对其1年生与2年生主根中部的结构进行了比较分析.结果表明,北柴胡根的发育包括原分生组织、初生分生组织、初生结构和次生生长4个发育阶段.原分生组织由3群原始细胞组成,其细胞具有典型分生组织的细胞学特征;初生分生组织包括根冠原、表皮原、皮层原和中柱原.初生结构由表皮、皮层和中柱组成.初生木质部为二原型.次生生长主要是依靠维管形成层和木栓形成层的活动来完成.其木栓形成层由中柱鞘细胞恢复分裂能力而形成.2年生北柴胡主根的基本结构与1年生的相同,但与1年生的相比,其周皮、次生韧皮部和木质部面积均增加.不同点具体表现在:2年生主根的周皮增厚;分泌道数量增加;次生木质部中木纤维成群分布,在横切面上连接成一个圆环,其维管射线明显,多为多列射线.分泌道主要分布在中柱鞘薄壁组织和次生韧皮部中,均是裂生方式发生,属次生分泌道,初生结构中无分泌道存在.

The development of Bupleurum chinense DC. roots was studied by observing the tips and central parts of one-year-old and two-year-old Bupleururn chinense DC. taproots transversely and longitudinally by paraffin sectioning ,and the central structures of the one-year-old and two-year-old taproots were comparatively analyzed. The results showed that the development of Bupleururn chinense DC. roots could be divided into four stages, promeristem, primary meristem, primary structure and secondary stages of growth. The promeristems consisted of three groups of primitive cells,which had the cytological characteristics of typical meristem cells;the primary meristems were composed of calyptrogens, primordial epidermises, periblems and pleromes. The primary structure consisted of epidermises,cortex and stele. The primary xylem were diarch. The secondary growth mainly relied on the activities of vascular cadmium and cork cadmium; the cork cadmium formed from pericyclic cells that resumed their dividing capabilities. The one-year-old and Bupleururn chinense DC. taproots were the same as the two-year-old ones in basic structure but in- creased in its periderm,secondary phloem and xylem areas copmared with （he two-year-old ones. The two taproot types showed their differences in the following respects; the two-year-old taproots increased in periderm thickness and secretory canal number,had secondary xylems whose woody fibers distributed in aclumped manner and transversely formed a cycle that presented clear vascular rays most of which were muhiseriate ones. The secretory canals,mainly distributing in the pericyclic parenchymna and secondary phloem,and occurring in a spallation produced manner,were secondary ones and did not appeared in the primary structure.