Iodine-Enriched Urea Enhances Maize Tolerance to Water Deficit via Modulation of Pigments and Sugars

Water deficit (WD) impairs maize growth, but the application of beneficial elements such as iodine (I) has shown potential to mitigate WD. Nevertheless, strategies for incorporating I into the soil are still needed. In this context, the present study incorporated I into urea (I-enriched urea) at different I rates (0, 750, 1500, and 3000 g I hectare^-1) and evaluated its potential to alleviate WD in maize plants. For this purpose, maize plants were grown in Oxisol samples under simulated WD conditions and compared with plants grown without water limitation. Several parameters were evaluated during and after the stress period, including physiological parameters, pigment content, antioxidant activity, levels of compatible osmolytes, shoot dry matter, and shoot nitrogen (N) accumulation. Under WD conditions, the application of 1500 and 3000 g I hectare^-1 via I-enriched urea, compared with no I application, increased the leaf electron transport rate and relative water content (RWC) while reducing membrane damage. These responses were directly associated with increased chlorophyll a, b, and total contents, and with lower levels of catalase and phenolic compounds. This effect also resulted in reduced superoxide dismutase (SOD) levels after the stress period. Moreover, in the first evaluation of irrigated plants, I-enriched urea promoted greater N uptake, increasing N accumulation in the shoot. Thus, the use of I-enriched urea at I application rates of 1500 and 3000 g I hectare^-1 proved to be a promising strategy for mitigating WD. The results shown here have future implications that need validation under field conditions. Still, they suggest that I-enriched urea may be a viable agronomic approach to increase maize tolerance to WD and has high potential for integration into nutritional management strategies in environments subject to drought or irregular rainfall during maize growth.