xylem

例句：

1. 1. The tree's xylem is the main part of its structure.
   这棵树的木质部是其结构的主要部分。
2. 2. The xylem carries water and nutrients from the roots to the leaves.
   木质部将水分和养分从根部输送到叶子。
3. 3. Xylem is essential for plant growth and survival.
   木质部对植物的生长和生存至关重要。