牛膝(苋科)轴器官中异常结构的研究

The Anomalous Structures of Achyranthes bidentata Blume(Amaranthaceae)

应用植物解剖学方法研究了牛膝（Achyranthes bidentata Blume）轴器官中异常结构的发育过程。研究结果表明，在牛膝根的发育过程中，其初生生长和早期的次生生长类似于一般双子叶植物。以后在正常维管柱的外围发生4—5轮额外形成层，并以双向活动方式形成同心环状排列的三生维管束和其问的薄壁结合组织。而在牛膝的茎中存在两种不同类型的异常结构。在茎的发育过程中，当次生维管束分化将完成时，由其外侧保留的1～2层原形成层细胞恢复分裂能力产生一轮额外形成层，额外形成层活动形成一轮三生维管束。茎中的2个外韧型髓维管束也来源于原形成层，与正常维管束在位置上没有相关性，但其结构类型存在多样性，有时可形成不完全的周木型髓维管束。

The developmental and the anatomical structures of anomalous structure in the axes of Achyranthes bidentata were examined with anatomical methods. The results showed that the primary and initial secondary growth of the root resembled those of usual dicots. Afterwards ,4 - 5 rings supernumerary cambiums occurred centrifugally. Each cambium produced tertiary vascular bundles and conjunctive tissues in a bidirectional manner. However, there were two types of anomalous structures in the stem of A. bidentata. In the development of stem,when the differentiation of secondary vascular bundle was finished, a ring supernumerary cambium originated from the one or two layers cells of procabium which remained the outside of secondary vascular bundle. And the activities of the supernumerary cambium produced the tertiary vascular bundle. In addition, there was no correlation between the two medullary bundles that also originated from procambium and normal vascular bundles in the position. But there were muhiformity on the types of the structure of medullary bundle. And sometimes incomplete amphivasal bundles were formed.