Selenium (Se) is a nutrient whose daily intake is often below the recommended levels in people. Biofortification with Se is a method to increase this intake by raising the Se concentration in tomato fruits, an effect dependent on sources and modes of application. Additionally, Se application can promote the enhancement of other compounds in tomato fruits, altering their metabolism, which may increase the fruit’s shelf life. This study aimed to determine how different strategies of applying a multi-nutrient fertilizer containing Se (SeMNF) can increase the Se content and other bioactive compounds and enhance the shelf life of tomato (Solanum lycopersicum L.) fruits. Different foliar fertilization strategies involving the use of SeMNF were evaluated in field trials conducted on commercial tomato crops. Indeterminate-growth tomatoes were used, and different Se doses and application strategies were tested. Harvesting was conducted in three phases according to fruit ripening. Each harvested fruit was assessed for the Se content, macro and micronutrients, total phenolic compounds, vitamin C, antioxidant activity, carotenoids, pH, total titratable acidity, and total soluble solids in tomato fruits. Doses of 15 g ha⁻¹ of Se, split into three applications, increased the Se content in the fruits at 1 and 2 harvests. The application of SeMNF at Se doses above 10 g of Se ha⁻¹ increased firmness, days of ripening, and the nutritional quality of the tomatoes (higher contents of carotenoids (+39%), lycopene (+33%), antioxidant activity (+16%), total phenolic compounds (+38%), and vitamin C (+14%) in a dose-dependent effect of the application strategy used. These results contributed to an increase in the shelf life of tomatoes, consequently reducing food waste.

Agronomic biofortification strategies have been used to increase selenium (Se) concentrations in edible parts, with broccoli cultivation showing high potential. Recent studies have demonstrated that prior application of selected elements during the seedling phase (priming) can enhance agronomic biofortification when this element is applied during the adult phase; however, no such effect has yet been reported for Se. Additionally, Se concentration in broccoli florets may be affected by post-harvest processing, thus determining losses is essential in the agronomic biofortification process. This study aimed to determine whether seedling production with priming using selenium (Se) could enhance different agronomic biofortification strategies for Se, and to evaluate the effect of post-processing on the Se concentration in broccoli. Seedlings were produced with and without priming (75 mg L⁻¹ of Se), and different application methods (soil and foliar), sources, and doses of Se were tested on Se concentration in broccoli florets. Foliar application strategies for Se were more effective than soil application for producing Se-biofortified broccoli. Seedlings produced and subjected to Se application to promote the priming effect enhanced Se absorption and increased Se concentration in broccoli florets. However, the highest Se absorption with a dry mass concentration exceeding 18 mg kg⁻¹ reduced broccoli production, except for Se applied via multi-nutrient fertilizer. Foliar fertilization strategies using 50 g of Se ha⁻¹ via multi-nutrient fertilizer, Se + organic compounds, and sodium selenate, along with the use of seedlings produced with priming and the application of 50 g of Se ha⁻¹ via multi-nutrient fertilizer using seedlings produced without priming, can provide Se amounts reaching the human dietary requirement of 60–70 µg day⁻¹, based on the adequate daily consumption of broccoli (40 g of broccoli). Different processing stages do not cause significant losses of Se in biofortified florets. Therefore, it is concluded that seedlings produced with priming combined with foliar Se applications are effective strategies for promoting agronomic biofortification of Se in broccoli florets for the human diet.

Iodine is a non-essential element for plants, yet recent studies have shown that it plays a role in mitigating abiotic stress. Heat stress (HS) and water stress (WS) impair maize growth and development, especially during the reproductive phase. This study evaluated whether iodine applications could mitigate HS and combined HS + WS during maize flowering. The experiment was conducted under greenhouse conditions, growing maize plants in pots containing 3 kg of Oxisol. Treatments included foliar or soil applications of iodine under two stress conditions (HS and HS + WS). Iodine was applied to the soil via top dressing and as a foliar application at the start of flowering. On the last day of stress, chlorophyll levels, specific enzyme activity, compatible osmotic solutes, relative water content (RWC), and Fv:Fm (photosynthetic quantum efficiency) were measured. Grain yield was determined at the end of the crop. There was no mitigation of stress with iodine application under combined stress (HS + WS). Under HS, foliar application of iodine, compared with no iodine application mitigated stress, increasing Fv:Fm by 58% (values of 0.73 for foliar iodine application versus 0.02 for no iodine application), RWC by 83% (values of 99% for foliar iodine application), and grain yield by 35%, along with higher levels of chlorophyll a (+28%), chlorophyll b (+73%), total chlorophyll (+31%), and superoxide dismutase activity (SOD). This was also associated with a reduction in sucrose, reducing sugars, total soluble sugars, and total free amino acids. This increase in chlorophyll levels suggests greater photosynthetic capacity, while the higher SOD activity indicates a strengthened antioxidant system under HS. These mechanisms together maintain carbon assimilation and reproductive development, thereby increasing grain yield. Thus, it was concluded that iodine could help reduce HS effects during maize flowering.

Heat stress limits raspberry cultivation in tropical and subtropical regions, yet strategies to mitigate its effects on seedlings are scarce. Selenium (Se) and iodine (I) individually enhance plant tolerance to abiotic stress, but whether their combined application produces complementary effects on the physiological responses of heat-stressed raspberry seedlings remains unexplored. This study addressed this gap by evaluating the physiological, biochemical, and photosynthetic responses of ‘Heritage’ raspberry seedlings to foliar applications of Se and I, alone and in combination, under high-temperature conditions. The experiment used a completely randomized design with ten treatments: one non-stressed control (0 mg L⁻¹ Se and 0 mg L⁻¹ I) and nine heat-stressed treatments. Among the stressed treatments, one received no selenium or iodine (0 mg L⁻¹ Se and 0 mg L⁻¹ I) and served as the stressed control. The remaining eight treatments received combinations of selenium (0, 25, and 50 mg L⁻¹) and iodine (0, 50, and 100 mg L⁻¹). One week after foliar application, seedlings were exposed to heat stress under controlled conditions of 40/18 °C (day/night) for three days. Physiological, biochemical, antioxidant, and chlorophyll fluorescence parameters were evaluated during and after the stress period. During heat stress, intermediate Se and I combinations helped maintain plant water status and photosynthetic performance, although the physiological and biochemical responses varied across treatments and sampling times. After the stress period, these treatments promoted osmotic adjustment and improved antioxidant regulation, contributing to the recovery of raspberry seedlings. Principal component analysis reinforced the association between intermediate Se and I combinations and mechanisms related to antioxidant regulation, osmotic adjustment, and photoprotection. Collectively, these findings indicate that co-application of Se and I triggers complementary physiological mechanisms of heat-stress acclimation in raspberry seedlings, suggesting a promising strategy for enhancing seedling tolerance to high-temperature stress.

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.