Effect of 24-Epibrassinolide Plant Hormone Rates on the Level of Macronutrients in Forage Sorghum Plants Subjected to Water Deficit and Rehydration

Forage sorghum (Sorghum bicolor (L.)) is a cereal native to Africa and belongs to the family Poaceae. It is a forage with a C4 photosynthetic pathway that stands out for its ability to adapt to different environments; it is able to produce even in unfavorable circumstances. The objective of this study was to analyze the attenuating effect of the brassinosteroid hormone in the form of 24-epibrassinolide on forage sorghum plants subjected to water deficit and rehydration. A completely randomized design (CRD) was used in the experiment. A 2 × 3 × 5 factorial arrangement was used, with two water conditions (water deficit and rehydration), three brassinosteroid doses (0 nM, 50 nM, and 100 nM as 24-epibrassinolide), and five replicates. The experiment was conducted in a greenhouse. Sorghum seeds were sown in pots with a capacity of 3 kg of substrate. Analyses were performed on the roots and leaves of sorghum plants at different growth stages. The macronutrients (N, P, K, Ca, and Mg) were analyzed in the soil physics laboratory. As a result, the content of N, P, K, Ca, and Mg decreased under a water deficit and was then restored by the hormone 24-epibrassinolide, which was able to restore these nutrients. The effect of the hormone under rehydration had a positive effect, increasing the levels of nutrients. Given the above, it was possible to conclude that there were no significant divergences between the treatments during the period of irrigation suspension. Among the tested concentrations, 50 nM of 24-epibrassinolide showed the most consistent improvements in nutrient concentrations under water-deficit conditions, suggesting a potential role in mitigating nutritional imbalance during stress. Rehydrated plants maintained nutrient levels similar to the controls regardless of 24-epibrassinolide application. However, it is important to note that nutritional quality indices such as crude protein and total digestible nutrients (TDN) were not evaluated in this study, which limits direct conclusions about the forage nutritional value.