Many vessel numbers, small pore, libriform fibres (mechanical tissue)and obvious secondary thickening of xylemtissue are the features of adaptation to the environment.
红树植物导管数量多、管孔小、机械组织为韧型纤维，薄壁组织次生加厚明显是适应环境的特征。
2
Tree rings are made of tissue called xylem.
构成年轮的组织被称为木质部。
3
The results showed that all the cross branch roots of different sizes consisted of periderm, secondary vascular tissue and tetrarch primary xylem.