Biostimulation with Se, I, Co, Si and Saccharomyces cerevisiae improves growth and flowering of Eustoma russellianum

Lisianthus (Eustoma russellianum (Hook.) G. Don) is a high-value ornamental species, but several biotic and abiotic factors can affect its floral quality and market competitiveness. In this study, the effects of different doses of selenium (Se; 12, 24, and 48 µM), cobalt (Co; 21, 42, and 84 µM), iodine (I; 24, 48, and 96 µM), silicon (Si; 1, 2, and 4 g), and yeast extract (Saccharomyces cerevisiae; 3, 6, and 12 g), applied to the substrate, were evaluated on plant growth. (height, stem diameter, leaf number, and fresh weight), floral traits (floral bud number, polar and equatorial diameters, flower weight, and petal number), and mineral content (P, K, Ca, Mg, and S). Plant height and leaf number generally increased with treatments, whereas stem diameter and fresh weight were mainly enhanced by yeast extract, iodine, silicon, and selenium. During the reproductive phase, floral bud number increased mainly with yeast extract, followed by iodine and silicon; flower weight increased with iodine and cobalt; and equatorial and polar diameters were promoted by yeast extract, iodine, and silicon, although cobalt increased polar diameter while reducing equatorial diameter. All treatments increased petal number. Regarding mineral content, yeast extract and cobalt increased phosphorus (P); calcium (Ca) increased with yeast extract; magnesium (Mg) with cobalt; and sulfur (S) with selenium, iodine, silicon, and yeast extract, whereas potassium (K) decreased with biostimulant application. Overall, biostimulants improved morphological traits and modulated mineral accumulation in lisianthus, highlighting yeast extract, iodine, and silicon as the most promising inputs.