Comparative Effectiveness of Iodine Nanoparticles and Potassium Iodide on Nitrogen Assimilation, Biomass, and Yield in Lettuce

Efficient nitrogen assimilation in crops remains a key challenge for sustainable agriculture. This study investigated the physiological effects of foliar application of iodine on <i>Lactuca sativa</i> L. cv. Butterhead, comparing two different chemical forms—nanoparticulate iodine (INPs) and potassium iodide (KI)—selected to contrast a conventional ionic source with a nanoformulations of growing interest in plant nutrition. Plants were treated under passive hydroponic conditions with INPs and KI at concentrations of 40, 80, and 160 µM. The results showed that INPs at 40 µM significantly increased total biomass and soluble amino acid accumulation compared to the control, with no signs of phytotoxicity. In contrast, KI treatments significantly increased nitrate reductase activity, suggesting a role in the activation of the nitrogen pathway. However, neither form consistently outperformed the other across all evaluated variables. Yield and total chlorophyll content remained statistically unchanged between treatments, indicating a complex and form-dependent response. These findings highlight the differential physiological effects of iodine formulations on nitrogen-related metabolism and provide preliminary evidence for their potential integration into precision fertilization strategies focused on biochemical efficiency and metabolic modulation.