Bioprospecting Pantanal Aquatic Macrophytes as Sources of Plant-Derived Biostimulants for Soybean Seed Treatment

The Pantanal biome harbors a high diversity of aquatic macrophytes that remain largely unexplored as potential sources of plant-derived agricultural biostimulants. This study evaluated six aquatic macrophytes from the Pantanal: Eleocharis cellulosa, Pistia stratiotes, Thalia geniculata, Pontederia sp., Pontederia rotundifolia, and Pontederia azurea as potential sources of plant-derived biostimulants. Aqueous and methanolic extracts were prepared by dynamic maceration and tested on soybean seed treatment. FTIR spectroscopy was used to characterize functional groups. Final germination percentage ranged from 86% to 97% across treatments, and no extract significantly reduced this endpoint compared with the respective controls, indicating the absence of detectable phytotoxic effects under the tested conditions. P. rotundifolia, T. geniculata, and P. azurea promoted increases in biomass and length (up to 0.44 g of epicotyl dry mass and 14.62 cm of root length), emerging as promising biostimulant source. E. cellulosa and Pontederia sp. showed neutral or negative effects on most growth variables. P. stratiotes remained neutral. FTIR analysis revealed distinct spectral profiles between extraction methods. Aqueous extracts showed prominent absorption bands associated with carbohydrate and polysaccharide-related functional groups, whereas methanolic extracts exhibited additional bands consistent with phenolic, aromatic, ester, and lipid-associated functional groups. The aqueous route stood out for producing bioactive extracts without organic solvents, a key advantage for sustainable scaling.