杜梨根端结构及其初生组织分化

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 ROOTS-APEX STRUCTURE OF P YR US BETULAEFOLIA AND ITS DIFFERENTIATION OF PRIMARY TISSUE

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.