It is constantly replaced by newly formed cells as the older tissue is sloughed off with growth of the root through the soil.

• 随着根尖的生长，根冠外层的薄壁细胞与土壤颗粒磨擦，不断脱落，死亡，由其内的分生组织细胞不断分裂，补充到根冠，使根冠保持一定的厚度。