## 4 Discussion
amounts inhibit them [19; 37; 39]. Based on their own experimental data and on studies by other authors, [PERSON] and [PERSON] [19] hypothesize that the effects of Ti are based on Fe activity. [PERSON] and [PERSON] [40] showed an increase in Fe\({}^{2+}\) content in leaves, fruit, chloroplasts and chromoplasts after foliar application of Ti (IV) ascorbate. Taking this into account, [PERSON] and [PERSON] [19] hold that in plants Fe\({}^{2+}\) is a metabolically active form of Fe and a mobile fraction [41]. The latest theory proposed by [PERSON] et al. [38] assumes that the beneficial role of Ti in plants lies mainly in interactions with other nutrients, especially Fe. This hypothesis was extended by those authors with the conclusion that Ti and Fe can form both synergistic and antagonistic compounds. When plants lack Fe, Ti can induce the expression of genes associated with the metabolism of Fe, i.e., increasing its uptake and retention, which consequently leads to improved plant growth as plants may have proteins capable of specific or nonspecific binding to Ti. When the Ti content of plant tissues is high, Ti can compete with Fe for ligands or proteins. The phenomenon of competition can be dangerous for plants due to the high level of Ti toxicity [38; 42]. According to [PERSON] et al. [43], the higher productivity of plants treated with biostimulants is primarily attributed to greater nutrient absorption, osmotic regulation, and increased content of many secondary metabolites. The above findings can be summarized by the conclusions of studies conducted by [PERSON] and [PERSON] [44], who found that positive physiological effects can be achieved using small doses of biostimulants, resulting in higher yields with better quality, and--ultimately--higher incomes for farmers. The present research shows that natural biostimulants are an effective tool to be used in the management of grassland to stimulate plant growth and productivity. Their use in conditions of unpredictable climatic changes constitutes a sustainable and environmentally friendly agronomic practice. However, what is needed is continuous development and expansion of knowledge about their effects and the reaction of specific crops to such biostimulants. The results of the research indicate not only a significant increase in the dry matter yield, but also a modification of the chemical composition of _Poa pratensis_ meadow plants, compared to control. The results indicate that the use of each biostimulant increased the _Poa pratensis_ dry matter yield, but better results were recorded after using both together. Additionally, the products significantly affected the concentration of macronutrients in plants. Statistical methods as Mahalanobis distances and correlation analysis are often applied in agriculture [45; 46; 47]. It should be emphasized that despite the diversity of studies reported in the literature, their results and hypotheses indicate an incomplete understanding of the mechanism of biostimulant action, especially Ti. All the theories presented above have both strengths and weaknesses. For this reason, more research is needed to determine the mechanism of Ti action.