Priming Effect of Seeds with Niobium (Nb) on the Performance of Maize Plants Under Water Deficit Conditions

Water deficit is a limitation to maize (Zea mays L.) productivity, and seed physiological conditioning (priming) is a strategy to mitigate its effects. Niobium (Nb), an abundant element in the Earth's crust and crucial for emerging technologies, is primarily produced and exported by Brazil, particularly in the state of Minas Gerais. However, its behavior in soil and effects on plants remain poorly understood. This study evaluated the impact of maize seed hydropriming with different solutions, including ammonium niobate (V) oxalate (C₄H₄NNbO₉), on germination, seedling physiological performance under water deficit, and recovery after rehydration. The experiment was conducted in a greenhouse using a randomized block design with eight treatments and five replications. The germination speed index (GSI) was recorded over a period of seven days. Water deficit was imposed on day eight by suspending irrigation for seven days, followed by rehydration until day 21. Morphological, biochemical, and physiological traits were evaluated, including biomass, pigments, oxidative stress, antioxidant activity, starch, and osmolytes, with photosynthetic parameters measured during rehydration. Hydropriming with Nb-enhanced seed germination but also induced oxidative stress and reduced biomass accumulation. Nb seed priming affected photosynthetic performance in a treatment-dependent manner, leading to phototoxic effects. Overall, although Nb shows biostimulant potential by improving maize germination, its use under water-deficit conditions may trigger toxic responses associated with increased oxidative stress and growth inhibition. These findings highlight the need for further studies to define safe and effective Nb concentrations for improving drought tolerance.