杜梨根端结构及其初生组织分化

THE ROOTS-APEX STRUCTURE OF PYRUS BETULAEFOLIA AND ITS DIFFERENTIATION OF PRIMARY TISSUE

杜梨根端的结构,可分成中柱分生组织,皮层细胞和根冠。根端的分生组织区域,没有明显的分层现象,其中只能划分出中柱分生组织与其外面的皮层分生组织。中柱最前端可较早地分化出中柱的最外一层中柱鞘。中柱鞘内的中柱分生组织,先分化初生韧皮部中的筛管,但无伴胞,随后出现原生木质部极。中柱外面的皮层分生组织,将来发展成为皮层、表皮层和根冠。杜梨根端的内皮层外面,也具有菲增厚壁细胞层。

The structure of the root apex of Pyrus betulaefolia Bunge consists of the stelar meristem,cortical cells and the root cap.The meriatem area of the root apex has no con- spicuous layerings,but the stelar meristem and the outer cortical meristem are visible.The anterior portion of the stele differentiated rather early into an outer layer-pericycle.The stelar meriatem that was inside the pericycle eventually differentiated into sieve tubes,not accompanying with the companion cells,of the primary phloem and followed by the ap- pearance of the protoxylem pole.Outside of stele the cortical meristem developed into cortex,epidermis and the root cap subsequently.In this root apex the phi-thickening wall was also visible in the transverse section.