Halotolerant, plant growth-promoting rhizobacteria (PGPR) are known to alleviate plant growth under abiotic stresses, especially those isolated from saline arid soils. In this study, 66 bacterial isolates, obtained from various habitats in Saudi Arabia, were characterized for their plant growth-promoting (PGP) traits, and screened for heat and salt stress resilience. Finally, selected halotolerant PGPR strains were assessed for their potential to improve maize (Zea mays L.) growth under salinity stress using in vitro assays. Our results indicated that many isolates possessed key PGP traits such ACC deaminase, N-fixation, and phytohormone production. Additionally, several isolates were able to tolerate high temperatures, and 20 bacterial isolates were classified as halotolerant. Furthermore, among the isolates, Pseudomonas soyae (R600), Bacillus haynesii (SFO145), Salinicola halophilus (SFO075), and Staphylococcus petrasii (SFO132) significantly enhanced various maize growth parameters under salt stress conditions when compared to uninoculated plants. These halotolerant PGPR are good candidates to be explored as bioinoculants for sustainable agriculture under saline arid soil conditions.

High levels of antimony (Sb) adversely affect plant growth and development. We aimed to uncover the harmful effects of different forms of Sb on root morphology, physiology and expression profiles of genes encoding functions associated with roots. Rice plants grown in ½ Hoagland nutrient solution were exposed to Sb(III) and Sb(V) at concentrations of 10 and 20 mgL⁻¹ for one week. Results demonstrated that higher concentrations of Sb(III) significantly impaired root morphological traits, with high toxicity observed at 20 mgL⁻¹ Sb(III) and 10 mgL⁻¹ Sb(V). The application of Sb(III) led to reduced uronic acid levels in hemicellulose-II (HCII) with cell organelle and cytosol displaying substantial accumulation of Sb(III). Enzymatic activity revealed that high levels of Sb(III) disrupted the activity of cellulase (CE) and pectin methylesterase (PME), while augmenting the activity of Xyloglucan endotransglycosylase hydrolase (XTH). Additionally, polygalacturonase (PG) was significantly reduced under Sb(V) 10 mgL⁻¹ exposure. Pearson’s correlation coefficient was used for continuous data to draw a linear trend between studied parameters. Shoot biomass displayed a negative correlation with root and shoot Sb. Shoot XTH had a positive correlation with shoot Sb. Furthermore, root and shoot Sb showed a positive association with root diameter and XTH. Hemicellulose-1 (HCI) was negatively associated with PME, PG and pectin, suggesting that HCI was a suitable binding site for uronic acid in the context of Sb contamination. Additionally, to elucidate the molecular mechanisms underlying root structural alterations, the expression profiles of key cell wall-related genes—Expansin, Cellulase synthase, XTH8 (xyloglucan endotransglucosylase/hydrolases) and Pectinesterase—were systematically analyzed using qRT-PCR. All genes were up-regulated in response to different forms of Sb exhibiting resistance. Xylanase was down-regulated, showing its role in the containment of Sb in roots. Further studies are advised for elucidating the mechanism of action of Sb on different tissues of rice plants.