Biostimulant effects of aqueous extracts from wild and cultivated Ulva ohnoi Hiraoka & S.Shimada biomass on mung bean germination and seedling growth

Seaweed extract-based biostimulants have gained growing attention as sustainable tools for addressing the challenges of modern agriculture. However, the influence of biomass origin on their biological effectiveness remains poorly understood. This study evaluated the biostimulant properties of extracts from wild (SWE-W) and cultivated (SWE-C) Ulva ohnoi . The extracts of this green seaweed were tested at various concentrations (0.12%, 0.25%, 0.5%, and 1.0%) through seed germination and early seedling development bioassays in mung bean ( Vigna radiata ). Biostimulant activity was primarily driven by significant interactions between biomass source and the applied concentration across most measured variables. Seed treatment with either extract significantly improved germination performance and seedling growth at higher concentrations, whereas lower concentrations elicited responses comparable to or only slightly greater than those of the control. Principal component analysis (PCA) revealed distinct biostimulant response patterns: SWE-W was primarily associated with enhanced germination efficiency and biomass accumulation, whereas SWE-C was more closely linked to improved seedling elongation and vigor. These contrasting biological responses were accompanied by marked differences in extract composition influenced by biomass source, with SWE-C exhibiting higher contents of organic matter, total nitrogen, potassium, sulfur, calcium, and micronutrients. Among all treatments, 0.5% SWE-C exhibited the strongest stimulatory response, principally increasing the seedling vigor index by 34%, shoot length by 29%, and total length by 27% compared to the control. These findings demonstrate that aqueous U. ohnoi extracts can act as potent biostimulants during early mung bean development, underscoring the role of biomass origin in determining both chemical composition and biological efficacy.