Cadmium uptake by potato roots disrupts plant ion homeostasis, induces oxidative stress and inhibits plant growth

In this study, we used an integrated analytical approach to investigate early cadmium (Cd) stress responses in potato ( Solanum tuberosum ). Plant growth, root tip cell viability, and lipid peroxidation analyses were combined with bulk ionomics, root suberin chemistry, and spatially resolved elemental imaging by micro-particle induced X-ray emission (µ-PIXE) to link Cd uptake, nutrient homeostasis, tissue-level distribution, and physiological stress responses. Plants were exposed to 0, 50, and 200 µM Cd for short-term periods (1, 3, and 7 days) to capture pre-symptomatic and toxic phases of Cd stress. Cd was strongly retained in roots (4,472-11,442 mg Cd Kg⁻¹), particularly in cortical tissues, and only weakly translocated to shoots (translocation factors 0.070–0.085). A pre-symptomatic phase was identified at 50 µM Cd after 3 days, as no growth inhibition or oxidative damage was detected under these conditions. Despite this, substantial ionomic changes were already observed, including marked reductions in several mineral nutrients, most notably copper (88% and 50% reduction in roots and shoots, respectively) and zinc (32% reduction in shoots), together with a 27% increase in root iron concentration. µ-PIXE analysis revealed cortical enrichment of magnesium and zinc, as well as peripheral accumulation of iron and manganese. Although Cd exposure slightly altered suberin monomer composition, total suberin load remained unchanged (~14 µg mg⁻¹). Together, these results show that early Cd stress responses in potato are characterized by rapid disruptions in mineral homeostasis prior to detectable oxidative damage or growth inhibition, while overall suberin deposition remains stable. This suggests that the initial response to Cd stress may rely primarily on functional regulation of pre-existing barrier properties and ion transport processes rather than on major structural remodeling. These findings provide a physiological framework for developing breeding and management strategies aimed at limiting Cd accumulation in potato crops.