Enhancing plant establishment via rhizosphere signaling and hormonal regulation through biopolymer-mediated soil pore restructuring

Aims Coarse-textured sandy soils impose major constraints on plant establishment due to low cohesion, rapid drainage, and limited regulation of rhizosphere water and nutrient availability. We evaluated ethanol-precipitable material (EPM), a microbially derived extracellular biopolymer from Rhizobium tropici, as a soil amendment and compared its effects with xanthan gum (XG) to determine how biopolymer-mediated pore restructuring influences root development and plant performance. Methods Synchrotron X-ray micro-computed tomography (µCT) and unconfined compressive strength testing were used to characterize changes in soil pore architecture and mechanical behavior. Plant growth responses were quantified through biomass and root morphology measurements. Elemental composition was determined by X-ray fluorescence (XRF), while RNA sequencing (RNA-seq) and RT-qPCR were used to assess transcriptional responses associated with root development. Results Both biopolymers increased soil strength and reduced porosity; however, they generated distinct pore architectures. EPM produced spatially uniform reinforcement while maintaining pore connectivity, whereas XG induced localized densification and increased pore heterogeneity. EPM significantly enhanced plant establishment, increasing Bermuda grass biomass by more than fourfold and promoting extensive root proliferation, while XG provided little or no growth benefit. Elemental analysis indicated improved nutrient acquisition under optimal EPM concentrations. Transcriptomic and RT-qPCR analyses revealed coordinated regulation of cytokinin turnover, auxin-associated signaling, flavonoid biosynthesis, and redox pathways, consistent with enhanced lateral root development. Conclusions EPM-mediated pore restructuring promotes plant establishment by maintaining rhizosphere accessibility while enhancing soil stability. These findings identify pore architecture as a key regulator linking root developmental responses and plant performance in degraded sandy soils.