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1·Primary phloem PHLOEM derived from the procambium in the young plant.

初生韧皮部：指幼嫩植物中来源于原形成层的韧皮部。

2·Secondary structure occurs in the root hair zone, and vascular cambium is formed from the parenchyma cells between the primary xylem and primary phloem;

次生结构发生于根毛区，维管形成层由初生木质部和初生韧皮部之间的薄壁细胞转化形成；

3·Between primary xylem and primary phloem there are 2-3 layers of parenchymatous cells, regularly or irregularly arranged, but no cambial zone can be recognized.

初生木质部与初生韧皮部之间可见到2—3层排列规则或不规则的薄壁组织细胞，但是没有维管形成层的发生。

4·But boron also exhibits rapid and significant phloem mobility in species for which sorbitol, mannitol, or dulcitol are the primary photosynthates since these polyols can effectively complex boron.

而对于以山梨醇、甘露醇、半乳糖醇等多元醇为光合作用初级运输物的植物中，硼可以与多元醇形成络合物而在韧皮部中自由运输。

5·The stele includes all primary tissues derived from the procambium consists of pericycle, phloem and xylem.

中柱包括从原形成层衍生而来的全部初生组织，由中柱鞘、韧质部和木质部组成。

6·The stele includes all primary tissues derived from the procambium consists of pericycle, phloem and xylem .

中柱包括从原形成层衍生而来的全部初生组织，由中柱鞘、韧质部和木质部组成。

7·Primary vectors for transmitting phytoplasma are insects feeding on the sap of phloem, such as leafhopper, and psylla.

植原体病原主要依靠吸食植物韧皮部的昆虫介体传播，如叶蝉、木虱等。