Root cell wall (RCW) modification is a widespread important defense strategy of plant to cope with trace metals. However, mechanisms underlying its remolding in cadmium (Cd) accumulation are still lacking in hyperaccumulators. In this study, changes of RCW structures and components between nonhyperaccumulating ecotype (NHE) and hyperaccumulating ecotype (HE) of Sedum alfredii were investigated simultaneously. Under 25 μM Cd treatment, RCW thickness of NHE is nearly 2 folds than that of HE and the thickened cell wall of NHE was enriched in low-methylated pectin, leading to more Cd trapped in roots tightly. In the opposite, large amounts of high-methylated pectin were assembled around RCW of HE with Cd supply, in this way, HE S. alfredii decreased its root fixation of Cd and enhanced Cd migration into xylem. TEM and AFM results further confirmed that thickened cell wall was caused by the increased amounts of cellulose and lignin while root tip lignification was resulted from variations of sinapyl (S) and guaiacyl (G) monomers. Overall, thickened cell wall and methylated pectin have synchronicity in spatial location of roots, and their coordination contributed to Cd accumulation in S. alfredii.

根细胞壁（RCW）修饰是植物应对痕量金属的重要防御策略。但是，在超级蓄能器中仍缺乏重塑镉（Cd）的基础机理。本研究同时研究了东南景天的非累积生态型（NHE）和超累积生态型（HE）之间的RCW结构和成分的变化。在25μMCd处理下，NHE的RCW厚度是HE的2倍，NHE的增厚细胞壁富含低甲基化果胶，导致更多的Cd紧密地困在根中。相反，大量的高甲基化果胶在有镉供应的HE RCW周围组装，这样，HE S. alfredii减少了Cd的根固定，并增强了Cd向木质部的迁移。TEM和AFM结果进一步证实，细胞壁增厚是由纤维素和木质素含量增加引起的，而根尖木质化则是由芥子基（S）和愈创木基（G）单体引起的。总体而言，增厚的细胞壁和甲基化果胶在根的空间位置上具有同步性，并且它们的配位有助于S. alfredii中的Cd积累。