Foliar Application of Biostimulants Reprograms Antioxidants and Molecular Networks of Wheat Plants Grown in Saline-Alkali Environments.

Saline-alkali stress severely impairs plant growth by disrupting osmotic balance, inducing oxidative damage, and suppressing metabolic processes. This study investigates the efficacy of biostimulants including Trametes odorata extract (TOE), camphor, and xanthine, in mitigating Na2CO3-induced stress in wheat plants. Wheat (Triticum aestivum cv. Sakha 95) was grown under controlled conditions, with saline-alkali stress (100 mM Na2CO3) and weekly foliar treatments applied. After 60 days, comprehensive growth, biochemical, and molecular assessments were conducted. TOE exhibited a rich phytochemical profile, with soluble carbohydrates and alkaloids as major constituents in addition to high nitrogen and essential micronutrients, alongside significant antioxidant capacity. Na2CO3 stress reduced plant height, shoot water content, and photosynthetic pigments. Biostimulant applications reversed these effects, with TOE restoring Chl a and b, and xanthine enhancing carotenoids. Na2CO3 stress increased osmolytes (amino acids, proline, glycine betaine) but decreased soluble proteins. Biostimulants regulated these levels, with xanthine restoring soluble proteins to near-control values. Oxidative stress markers (H2O2, and MDA) were relieved by all biostimulants, with xanthine most effective in decreasing MDA. Antioxidant enzyme activities (SOD, APX) and stress-responsive gene expression (SOD, and CAT) were elevated under stress but differentially modulated by biostimulants, with TOE restoring homeostasis, while xanthine further enhanced MAPK and BADH expressions. TOE acted via ROS scavenging and nutrition, camphor boosted glutathione defense, while xanthine was associated with upregulated MAPK expression and enhanced flavonoid biosynthesis. Collectively, TOE, camphor, and xanthine effectively alleviated saline-alkali stress by enhancing antioxidant defenses, osmotic regulation, and photosynthetic efficiency, demonstrating their potential as sustainable crop stress mitigators.