We examined the subcellular cadmium (Cd) localization in roots and leaves of wild-type Arabidopsis thaliana (ecotype Columbia) exposed to environmentally relevant Cd concentrations. Energy-dispersive X-ray microanalysis (EDXMA) was performed on high-pressure frozen and freeze-substituted tissues. In the root cortex, Cd was associated with phosphorus (Cd/P) in the apoplast and sulfur (Cd/S) in the symplast, suggesting phosphate and phytochelatin sequestration, respectively. In the endodermis, sequestration of Cd/S was present as fine granular deposits in the vacuole and as large granular deposits in the cytoplasm. In the central cylinder, symplastic accumulation followed a distinct pattern illustrating the importance of passage cells for the uptake of Cd. In the apoplast, a shift of Cd/S granular deposits from the middle lamella towards the plasmalemma was observed. Large amounts of precipitated Cd in the phloem suggest retranslocation from the shoot. In leaves, Cd was detected in tracheids but not in the mesophyll tissue. Extensive symplastic and apoplastic sequestration in the root parenchyma combined with retranslocation via the phloem confirms the excluder strategy of Arabidopsis thaliana.

中文翻译：

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镉在拟南芥根和叶中的亚细胞定位。

我们检查了暴露于与环境相关的Cd浓度的野生型拟南芥（Ecotype Columbia）的根和叶中的亚细胞镉（Cd）定位。在高压冷冻和冷冻取代的组织上进行了能量色散X射线显微分析（EDXMA）。在根皮层中，Cd与质外体中的磷（Cd / P）和共生体中的硫（Cd / S）相关联，分别暗示了磷酸盐和植物螯合螯合剂的隔离。在内胚层中，Cd / S的螯合以液泡中的细颗粒沉积物和细胞质中的大颗粒沉积物存在。在中央圆柱体中，共生性积累遵循明显的模式，说明了传代细胞对Cd吸收的重要性。在质外体中 观察到Cd / S颗粒沉积物从中层向浆膜移。韧皮部中大量沉淀的Cd提示从芽中重新迁移。在叶片中，Cd在气管中检出，而在叶肉组织中未检出。根部实质中广泛的共生和质外分离螯合以及通过韧皮部的重新移位证实了拟南芥的排除策略。