Mowing facilitated Pb accumulation in bermudagrass by mediating root radial transport

Moderate mowing of the shoot is an effective strategy for improving Pb-contaminated soil remediation using bermudagrass. However, the mechanisms by which mowing facilitates Pb uptake and accumulation remain insufficiently understood. Root radial transport is critical in efficient heavy metal uptake and translocation in plants and is influenced by root physiological-biochemical characteristics. Herein, radial transport in roots and its effect on root-shoot Pb transport in bermudagrass under mowing were explored. Results revealed that mowing decreased Pb in apoplasts and increased Pb in symplasts, altering Pb radial transport pathways in roots. In the apoplastic pathway, mowing pretreatment intensified the inhibitory effects of a transpiration inhibitor on Pb uptake, resulting in a reduced contribution of the apoplastic pathway. Mowing induced lateral root endodermis thickening, early suberin lamellar development and increased suberin deposition, effectively preventing Pb from entering the stele through the apoplastic pathway. Conversely, in the symplastic pathway, mowing pretreatment alleviated the inhibitory effects of a metabolic inhibitor and ion channel inhibitor on Pb uptake and significantly increased net Pb²⁺influx in lateral root tips, thereby promoting the symplastic pathway. Furthermore, mowing upregulated the relative expression of CdNramp5 and CdHMA2 in roots, increasing Pb translocation to the shoot via the symplastic pathway. Overall, our study provided novel evidence mowing primarily improved Pb uptake and root-to-shoot transport by increasing the efficiency of the symplastic pathway. These findings provide a theoretical foundation for the use of mowing to improve the efficacy of bermudagrass in the remediation of Pb-contaminated soils.