牛膝根的发育解剖学研究

应用植物解剖学方法研究了牛膝(Achyranthes bidentataBlume.)根的发育过程.研究结果表明,牛膝根的发育包括原分生组织、初生分生组织、初生结构、次生结构和三生生长5个发育阶段.原分生组织具有典型分生组织的细胞特征;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.其内皮层细胞上凯氏带明显.初生木质部多为二原型;次生结构从外到内由周皮和次生维管组织组成,其木栓形成层由中柱鞘细胞恢复分裂能力而形成,次生结构中,次生维管组织占主要地位;牛膝根的进一步加粗主要是由于三生结构的发生和分化.第一圈额外形成层产生于次生韧皮部外侧的薄壁组织细胞和射线细胞,以后的每一圈由前一圈向外衍生的薄壁组织细胞产生.额外形成层无纺锤状原始细胞和射线原始细胞之分,在切向纵切面上呈叠生排列.三生维管束以离心方式排列成整齐的同心环状,由薄壁结合组织将其彼此分开,其圈数与额外形成层的圈数是一致的,随着根的个体发育而不断增加.

Development Anatomy of Achyranthes bidentata Roots

The developmental process of Achyranthes bidentata roots was examined by anatomical methods.It was shown that the development of A.bidentata roots included five developmental stages,promeristem,primary meristem,primary structure,secondary structure and tertiary growth stages.The promeristem possessed the characters of typical cambium cells,the primeristem included calyptrogens,dermatogen and plerome,and the primary structure was composed of epidermis,cortex and stele.The endodermis had clear Casparian strips on its cells.In most cases,the primary xylem was diarch and the secondary structure included periderm and secondary vascular tissue from the outer to the inner and its cork cambium developed from pericycle cells recovering their dividing capacity and vascular tissue dominated in the primary structure;A.bidentata roots further thickened because of the occurrence and differentiation of their tertiary structure.The first ring of extra cambium developed from parenchymatous and ray cells outside the secondary phloem and each following ring of extra cambium developed from parenchymatous cells deriving from its previous ring of extra cambium.The rings of extra cambium presented no differentiation into spindle-shaped and ray archaeocytes and appeared longitudinally overlapped.The tertiary vascular bundles were regularly,concentrically and centrifugally arranged and partitioned with connective parenchyma whose ring numbers were the same as that of extra cambium.