根砧木

例句：

1. 1. The tree's root system is extensive and deep.
   这棵树的根系广泛而深入。
2. 2. The scientist used a root-grow-indicator to monitor the plant's growth.
   科学家使用一种根生长指示剂来监测植物的生长。
3. 3. The roots of the tree are visible through the soil.
   树根在土壤中可见。