Nanopriming of Soybean [Glycine max (L.) Merr.] Seeds with Functionalized Multi-Walled Carbon Nanotubes: Effects of Concentration and Soaking Time

Nanotechnology applications in plants have enabled the development of seed treatments aimed at modifying germination and early seedling growth. Among these strategies, nanopriming involves seed conditioning with nanomaterials that may influence hydration, pregerminative metabolism, and redox balance. However, these interactions may produce stimulatory or phytotoxic responses depending on material properties, concentration, and imbibition duration, highlighting the need to establish crop-specific treatment conditions. This study evaluated the effects of functionalized multi-walled carbon nanotubes (f-MWCNTs), applied at different concentrations and soaking times, on germination and early seedling growth in soybean cultivar Brasmax Guepardo IPRO. A completely randomized 5×5 factorial design combined f-MWCNT concentrations of 0, 20, 40, 60, and 80 μg mL−1 with soaking times of 10 min, 6, 12, 18, and 24 h, plus a control of unprimed seeds not exposed to f-MWCNTs. Germination, abnormal seedling percentage, seedling height, shoot dry mass, and root dry mass were evaluated. Statistical analyses included analysis of variance, simple-effects analysis, a control-versus-factorial contrast, and regression analysis. The concentration × soaking time interaction significantly affected all traits except shoot dry mass, which responded only to soaking time and reached an estimated maximum at 8.17 h. The unprimed control had higher germination and a lower percentage of abnormal seedlings, whereas normal seedlings from the factorial treatment set were taller and had greater shoot dry mass. Among the primed treatments, the combination of 60 μg mL−1 and 10 min stood out by combining higher germination, a low incidence of abnormalities, and satisfactory early growth. Treatment effects were trait-specific, and the observed growth benefits did not demonstrate an overall improvement in seed physiological quality.