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This study investigated the proteomic and soluble metabolite profiles of maize ( Zea mays L.) root apices following 72 and 96 hours of seedling exposure to 10 mM and 100 mM NaCl, as well as 16% (w/v) polyethylene glycol 6000 (PEG). The highest NaCl concentration and PEG significantly reduced root length, whereas salinity increased root width, and PEG decreased it compared with non-stressed controls. Stress conditions induced changes in peroxidase isoform patterns. Across all samples, 3,357 unique proteins were identified in maize root apices. Gene ontology enrichment analysis of differentially accumulated proteins (DAPs) at 96 versus 72 hours under both salt and PEG treatments indicated redox metabolic adjustments. In both stress conditions, up-accumulated DAPs relative to controls were associated with the phenylpropanoid pathway, lignin precursor biosynthesis, cell wall-modifying proteins, and suberisation, consistent with observed reductions in aromatic amino acids. Salinity specifically upregulated the oxylipin biosynthetic process, lipid peroxide accumulation, and the glutamate catabolic process, resulting in increased GABA levels. Conversely, down-accumulated DAPs under salinity included enzymes involved in sterol biosynthesis, chaperones, chaperonins, and vacuolar V-type ATPase subunits. In water-stressed samples, nitrate assimilation, amino acid, and malate metabolism were among the most downregulated processes. While both salt and water stress similarly influenced apoplast-associated metabolic pathways, their distinct effects on downregulated processes in the apical zone may underlie their contrasting impacts on root width. These findings highlight cell wall remodelling as a central metabolic response, advancing our understanding of maize-specific sensitivity to salinity and drought stress.
Guaman et al. (Fri,) studied this question.