Sorghum and Hemp Responses to Plant Growth-Promoting Microorganism Inoculation in Metal-Contaminated Dredged...

Metal-contaminated dredged sediments represent heterogeneous environmental matrices in which remediation responses are frequently constrained by elevated background metal loads and complex geochemical conditions. Within such systems, phytoremediation has been discussed as a nature-based management approach whose outcomes depend on plant biomass, internal metal allocation, and context-dependent interactions between plants and sediment. The present study evaluated whether bacterial and fungal plant growth-promoting microorganisms (PGPMs) were associated with changes in plant metal uptake and internal allocation in Sorghum bicolor L. and Cannabis sativa L. grown in dredged sediment collected from the Bega Canal. An outdoor pot experiment was conducted under environmentally relevant conditions, including bacterial and fungal inoculation treatments alongside non-inoculated controls, with plant responses to Cr, Ni, Cu, Zn, As, Cd, and Pb characterized using concentration- and mass-based uptake metrics, root-shoot partitioning, and sediment geochemical assessment based on pseudo-total concentrations and BCR sequential extraction fractions. Across treatments, plant responses were largely governed by intrinsic species traits and biomass production, while PGPM-associated effects remained modest and variable. Root-dominated metal retention and limited translocation were evident irrespective of species, consistent with a phytostabilization-type response rather than systematic extraction. Absolute metal uptake accounted for only a minor fraction of total sediment metal pools, underscoring the importance of interpreting concentration-based indices jointly with mass-based metrics when evaluating system-scale responses. Altogether, the findings indicate that under the investigated outdoor dredged sediment pot conditions, PGPM inoculation acts primarily as a context-specific modulator of plant responses rather than a driver of enhanced phytoremediation performance, reflecting the central role of intrinsic plant traits and stabilization-oriented processes in complex sediment systems.