It is constantly replaced by newly formed cells as the older tissue is sloughed off with growth of the root through the soil. 隨著(zhù)根尖的生長(cháng)，根冠外層的薄壁細胞與土壤顆粒磨擦，不斷脫落，死亡，由其內的分生組織細胞不斷分裂，補充到根冠，使根冠保持一定的厚度。
The vascular cambium extends to form a complete ring of meristematic tissue around the stem, the separate vascular bundles being linked by interfascicular cambium. 維管形成層向兩側延伸直至形成一個(gè)莖內的分生組織環(huán)，各個(gè)維管束被束間形成層聯(lián)系在一起。
