牛膝茎的发育解剖学研究

应用植物解剖学方法研究了牛膝茎的发育过程。研究结果表明,牛膝茎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;初生分生组织包括原表皮、基本分生组织和原形成层。在茎的发育过程中,初生生长和早期的次生生长是正常的,但在次生生长过程中,次生维管组织仅有束中形成层产生,而没有束间形成层的分化和活动。茎的三生生长是由维管柱外侧保留的原形成层细胞发生的额外形成层的活动产生的。额外形成层开始只向内交替产生三生木质部和其间的结合组织,后来向外产生三生韧皮部,形成一轮三生维管束。牛膝茎内的韧皮纤维来源于原形成层,应属于原生韧皮部性质。牛膝茎中的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。但其结构类型具有多样性,有时可形成不完全的周木型髓维管束。

Developmental anatomy of the stem in Achyranthes bidentata

Developmental process of Achyranthes bidentata stem was examined by anatomical methods. It was shown that the development of A.bidentata stem included five stages:promeristem,primary meristem,primary structure,secondary structure and tertiary growth stages. The promeristem possessed the cytological characters of typical meristem,the primary meristem included dermatogen,ground meristem and procambium. In the course of stem development,primary and initial secondary growth was similar ordinary dicotyledons. Then as the fascicular cambium was initiated,the interfascicular cambium was not formed in the secondary growth of stem. The tertiary growth of stem was replaced by the activities of supernumerary cambium arising from procambium cells remaining the lateral vascular cylinder. Initially the supernumerary cambium formed tertiary xylem and conjunctive tissues alternately engender only on its inner side,and the differentiation of tertiary phloem strand which was produced in external to supernumerary cambium was later than that of xylem. The phloem fibers of A.bidentata stem originated from procambium belonged to characters of protophloem. In addition,there was no correlation between the two collateral vascular bundles which also originated from procambium and normal vascular bundles in the position. But there were multiformity on the structure of medullary bundle,and sometimes incomplete amphivasal bundles were formed.