原形成层

分枝列当茎的初生分生组织由原表皮、原形成层和基本分生组织组成。

Primary meristem of stem is composed of protoderm , procambium and ground meristem .

叶轴也来自叶原基和在中央区保留的原形成层细胞。

The leaf axis arises from the leaf buttress and maintains procambial continuity in the central region .

原形成层（原形成层束）：形成维管组织的一层细胞。

Procambium ( procambial strand ) The layer of cells that gives rise to the vascular tissue .

原生韧皮部：最早形成的初生韧皮部，由位于分生组织中的原形成层分化而来。

Protophloem The first-formed PRIMARY PHLOEM , differentiated from the procambium in the region just behind the meristem .

在原生韧皮部启动分化之前，所有原形成层细胞均显示与原形成层起始细胞基本相似的超微结构特征：细胞核大，具电子致密的异染色质；

Prior to the initiation of protophloem differentiation , all of the procambial cells showed ultrastructural characteristics basically similar to the procambial initial .

而生殖顶端只由一般分生组织和基本组织构成。原形成层在顶端分生组织之下叶原基起源的地方发生。

The procambium continuously develop to the apex after it arises from the place where the leaf primordia originates from below the apical meristem .

它并没有显示出在维管束周围的鞘状构造。原形成层（原形成层束）：形成维管组织的一层细胞。

It does not show sheaths around the vascular bundles . Procambium ( procambial strand ) The layer of cells that gives rise to the vascular tissue .

吸器中管胞和筛管都是从吸器中央具有原形成层特性的细胞分化的，管胞的分化先于筛管，或同时进行。

The tracheid and sieve tube elements are all differentiated from the procambia in the center of the haustoria , and the former occurs prior to the latter .