sieve cell

A typical veinal vascular bundle was composed of a few vessels, sieve tubes and companion cells, and the vascular parenchyma cells with large nucleus, thick cell wall and cytoplasm, and many organelles, especially mitochondria, in a vascular bundle.

大维管束由数个导管、筛管及伴胞和维管束薄壁细胞组成，且其维管束薄壁细胞壁厚、核大、质浓，线粒体丰富。

In the axial systems, the phloem consists of sieve cells, phloem parenchyma cells, albuminous cell and phloem fibers. In the radial systems, it consists of phloem rays.

轴向系统由筛胞、韧皮薄壁组织细胞、蛋白细胞和韧皮纤维组成，径向系统由韧皮射线组成。

The secondary phloem mother cell were divided and differentiated into sieve tube, companion cell, libriform fibre, parenchyma cell, and a few sclereid cells, The sieve tube and companion cell was originated from inequality mitosis of sieve mother cell.

维管形成层韧皮部母细胞分裂分化形成筛管、伴胞、韧皮薄壁细胞、韧皮纤维和少量的石细胞，筛管和伴胞来源于筛管母细胞的不均等有丝分裂。

Companion cells arrange in a row or single cell as long as the sieve tube member.

伴胞为与筛管分子等长的一列或单个细胞。

Programmed Cell Death ( PCD), a physiological cell death process, is associated with the differentiation of vessel and sieve tube, the propagation, senescence, the hypersensitive reaction of plants, and so on.

细胞程序性死亡（Programmed cell death，PCD）与导管和筛管的分化、繁殖、衰老、超敏反应等过程紧密相关。