primary xylem

Its root system is composed of adventitious roots. The primary xylem of root is 2~ 4 arches, and the secondary structure of root is characterized by a thicker phelloderm.

根系由不定根组成，根的初生结构木质部为2～4原型，次生结构中栓内层较厚。

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The primary xylem of root is diarch, of which developmental process contains primary growth and secondary growth. Secondary growth mainly depends on the activity of the vascular cambium and cork cambium.

其根为二原型，发育过程可分为初生生长和次生生长，成熟根的结构以次生结构为主，次生生长主要依靠维管形成层和木栓形成层的活动来完成。

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The correlation between the reducing sugar content in phloem and xylem and the ratio of damaged trees was not close. The stele includes all primary tissues derived from the procambium consists of pericycle, phloem and xylem.

不同杨树品系韧皮部和木质部的还原糖含量与被害株率没有相关性。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。

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

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。

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Protoxylem The PRIMARY XYLEM elements that are formed from the procambium first.

原生木质部:初生木质部的成分,最早由原形成层形成.

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The economic feature is obvious. shows that of all types casparian strip exits in endodermis and evident pith does in young root; primary xylem is exarch and tetrarch;

智囊团的经济特质是显而易见的。结果表明：内皮层都具有凯氏带，幼根均具有明显的髓，初生木质部均为外始式四原型；

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Results: The circular belt of sclereids in the phelloderm, secondary xylem vessel order of the transverse section, and tetrarch of the primary xylem were microscopic characters.

结果：根横切面上栓内层的石细胞环带和次生木质部导管的排列方式、初生木质部为四原型等为显微鉴别特征；

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Primary xylem Xylem derived from the procambium in the young plant.

初生木质部:指幼嫩植物中来源于原形成层的木质部.

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The results showed that all the cross branch roots of different sizes consisted of periderm, secondary vascular tissue and tetrarch primary xylem.

结果表明：不同直径大小的横走侧根均由周皮、次生维管组织和四原型的初生木质部构成。

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While for older roots, there are periderm, secondary phloem, cambium, secondary xylem and primary xylem. In root, the duct caliber of xylem in Akebia quinata ( Thunb.) Decne.

老根由外向内依次为：周皮、次生韧皮部、形成层、次生木质部、初生木质部。在根中五叶木通木质部导管口径比三叶木通的大很多。

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