怀牛膝根内部结构的研究

An Anatomical Study of the Root of Achyranthus Bidentata

报道了怀牛膝根的三生生长。其初生结构和次生结构类似于一般双子叶植物根。根的加粗主要是由于三生结构的分化和发生。第一圈额外形成层起源于次生韧皮部外侧相当于中柱鞘部位的薄壁细胞。以后的每一圈由前一圈向外衍生的薄壁组织细胞产生。栽培牛膝根中，通常有离心分化的四圈三生维管束排成整齐的同心环类型，三生维管束由薄壁结合组织彼此分开。三生维管束的圈数随根的个体发育增加，但并非同步进行，在一段时间内有相对稳定期。表皮细胞反分化而行平周分裂形成木栓形成层。

The tertiary growth in the root of Achyranthus bidentata was studied.The primary and secondary structures of the root resemble thoes of usual dicots.The thickening growth of the root principally results from the differentiation and development of the tertiary structure.The first ring of supernumerary cambium originates from the parenchtma analogous in position to the pericycle bounding the secondary phloem while each of the followed rings initiates in the outmost foundamental parenchyma derived from the immediate preceding ring.In cultivated plants, usually four regular and concentric rings of collateral tertiary bundles differentiate centrifugally enclosed by connective parenchyma.The number of the rings increase with,but not synchronously to, the development of the root itself,a relatively stable period exists.Cells of the epiblem dedifferentiate and divide periclinally to produce the phellogen.