Endodermal suberin deposition restricts potassium leakage from roots

O_LIThe endodermis is a checkpoint for ions and water escaping or entering the root. It has been hypothesized that suberin acts as a physical barrier preventing potassium (K) leakage from the stele during translocation, but attempts to support this idea has yielded contradictory results. C_LIO_LIWe developed a Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) based element bioimaging method to study K leakage from roots with different suberin deposition, where we show that cesium (Cs) is an excellent tracer for K. C_LIO_LIElement bioimaging of roots and total shoot concentrations from various Arabidopsis thaliana mutants all showed a positive relationship between suberin deposition and K translocation efficiency. In addition, images from the fully suberized barley (Hordeum vulgare) seminal roots revealed a strongly reduced K leakage compared to less suberized root zones. C_LIO_LINodal roots form a scattered deposition of suberin towards the phloem in the mature root zone. This incomplete suberin deposition also restrict K leakage efficiently. C_LIO_LICollectively, our findings provide experimental evidence that suberin act as a barrier for K leakage upon root-to-shoot translocation by restricting K movement over the endodermis from the stele to cortex. C_LI