BOOK OF ABSTRACTS 71 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Tuesday, 25 August 2026 / Hall B+C Research Frontiers SL29 From Black Box to Molecular Insight: Multi-Omics Elucidation of Fulvic Acid Biostimulant Action in Crops Mohsen Hesami1, Mohammad Rahbari1 1 BioLiNE® Corporation, Alvinston, ON, N0N 1A0, Canada; email: mhesami@biolinecorp.ca The agronomic efficacy of humic substances, particularly Fulvic Acid (FA), is well-recognized. The multiple mechanisms underlying crop response to FA have limited our understanding of the modes of action, leaving them largely as a black box [1]. This study presents a robust systems biology roadmap, integrating time-resolved transcriptomics (RNA-seq), untargeted metabolomics, and biochemical profiling, to decode how FA orchestrates drought resilience in Brassica napus and Zea mays. Our experimental framework evaluated FA efficacy under two distinct moisture regimes: well-watered (normal) and progressive drought stress. For the biochemical and morphological assessment in B. napus, four treatments were utilized: well-watered control (WWC), well-watered with FA (WWFA), drought control (DC), and drought with FA (DFA). For the molecular analysis, we focused on temporal dynamics by sampling at early (3 hours) and late (27 hours) intervals post-application. This design allowed for the identification of immediate signaling events versus downstream metabolic reinforcement, utilizing high-throughput sequencing and LC-MS/MS platforms to map the transition from gene expression to physiological phenotype. Results demonstrate that exogenous FA significantly mitigates droughtinduced oxidative damage. In B. napus, FA maintained cellular homeostasis by increasing soluble protein content and bolstering antioxidant machinery, specifically elevating catalase (CAT) activity and glutathione (GSH) levels (WWC < WWFA < DC < DFA). This biochemical reinforcement led to a marked reduction in malondialdehyde (MDA) and hydrogen peroxide (H2O2) accumulation, preserving membrane integrity and enhancing root architecture under severe osmotic stress. Temporal transcriptomic analysis identified that FA acts as a chemical eustressor, triggering a rapid „priming“ effect. Within 3 hours post-application, FA induced a bypass of traditional growth-stunting drought pathways in canola, instead activating membranelinked signaling and ROS-mediated defense genes. In maize, we identified a biphasic regulatory network: an early-stage (3h) upregulation of core transcription factor (TF) families, including ERF, NAC, and WRKY, which govern hormone signaling and ion transport. This was followed by a late-stage (27h) reinforcement of the phenylpropanoid biosynthetic pathway and redox regulatory networks.
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