Different substances from the natural origin which have beneficial effects on plant growth and development, stress resistance, and crop yield and quality can be called biostimulants or biostimulators. Their physiological effects depend on their composition as they contain various organic and mineral compounds which plants can use as metabolites, growth regulators, and nutrients; however, biostimulants cannot be considered biofertilizers. Biostimulants applied in plant production have been widely considered as an environment‐friendly agricultural practice—and so are now among tools used in sustainable agriculture. Here, we discuss the results of the biostimulants’ effect investigations performed in Croatia, focused on horticultural crops, with edible plant species, such as tomato, garlic, bell pepper, lettuce, strawberry, garden cress, and basil, as well as ornamentals, such as wild rose, wax begonia, Mexican and French marigold, moss rose, everlasting flower, common zinnia, English primrose, and scarlet sage. The investigated biostimulants were applied at all plant growth stages, from germination to full plant and fruit or flower commercial maturity, using the seed treatment, foliar application, or irrigation. To evaluate biostimulant effectiveness, various morphological, physiological, and quality traits were analyzed. In this wide array of studies, the evaluated biostimulants mostly enhanced seed and transplant vigor, stimulated vegetative growth, improved nutrient acquisition and distribution within the plant, increased antioxidative capacity of plant tissues, contributing to higher stress tolerance, and improved plant yield and fruit/flower quality. In general, the research reviewed here implies possible benefits of biostimulant application in horticultural production, especially in stressful growth conditions, such as the transplant stage, reduced fertilization, or incidence of other abiotic stress. Considering possible interactions among the contained physiologically active compounds, the effects on plants may depend on dose, time of treatment, growth conditions, and plant species. Therefore, further research of biostimulant applications in horticultural production is suggested.

Plant biostimulants are substances which have the capacity to modify physiological processes in plants in a way that provides potential benefits to growth, development or stress response. Effects of biostimulant application on two tomato hybrids (Ombeline F1 and Bostina F1) submitted to reduced nitrogen, phosphorus and potassium (NPK) nutrition aiming at prevention of oxidative stress generation as well as yield and fruit quality loss were investigated in this study. According to obtained results, foliar applied Viva® biostimulant decreased superoxide dismutase (SOD, EC 1.15.1.1) and peroxidase (POD, EC 1.11.1.7) activity in tomato leaves even when recommended NPK nutrition was reduced at 40%. Fruit quality parameters (total soluble solids, total acidity, ascorbic acid and lycopene content) and yield were also maintained in reduced macronutrient fertilization when biostimulant was added. Combination of biostimulant with reduced NPK fertilizer enabled stability of cell homeostasis in tomato plants and their better adaptation to stress conditions. The possibility of biostimulant being used as environmental friendly tool in the reduction of mineral fertilizers without negative consequences regarding yield and fruit quality was discussed.

Modern greenhouse pepper production should evolve towards more sustainable systems. The growing technique which combines soilless culture and biostimulants may reduce nutrient and water use with beneficial impact on the environment. Therefore, this work aimed to investigate effects of biostimulants application on hydroponically produced pepper plants (Capsicum annuum L.) in conditions of reduced fertilization. Positive influence of biostimulant treatment on yield parameters was observed along with significant decrease in incidence of blossom-end rot (BER) in two pepper cultivars. Biostimulants application resulted in overall increase in macro- and microelement content in fruits of treated pepper cultivars. Generally, biostimulants improved the yield of pepper plants grown hydroponically by increasing the nutrient uptake and decreasing the occurrence of BER. Thus, the application of biostimulants could be considered as a good production strategy for obtaining high yields of nutritionally valuable vegetables with lower impact on the environment.