Riboflavin-primed seeds reduce arsenic stress in Helianthus annuus L. through modulating antioxidant and metabolomics responses.

Heavy metals-induced stress disrupts plant growth and development, making their survival difficult. Arsenic (As) stress is one of the major constraints that have become obstacles to the successful cultivation of many oilseed plants, especially sunflower (Helianthus annuus L.). The current study aimed to estimate the capacity of riboflavin (Rib) to mitigate As stress in H. annuus. H. annuus seeds were primed with Rib (50 ppm) and grown in soil contaminated with As at 10 ppm per kilogram. Results demonstrated that As-stress negatively affected plant growth by increasing malondialdehyde (MDA) by 138.32% and electrolyte leakage to 54.43%. Stressed plants exhibited reduced antioxidant enzyme activities, reduced plant height to 40.5%, impaired gaseous exchange, and decreased photosynthesis to 22.30%, whereas Rib seed priming alleviated As toxicity by ameliorating membrane stability (from 45.57% to 55.80%), gas exchange, and enzymatic antioxidant activity (CAT, POD, APX) in treated plants. Moreover, Rib reduced MDA levels and increased chlorophyll content. The GC/MS-based non-targeted metabolic profiling indicated that seed priming with Rib could cause shifts in metabolites including sugars, amino acids, alcohols, carboxylic acids, and organic acids to augment H. annuus survival against metal stress. Our study demonstrates that seed priming with Rib can improve plant growth under metal stress in conventional agricultural systems.