The Effect of Larvae Hydrolysates on the Growth and Photosynthetic Apparatus of Beans

Background. Biostimulants are increasingly seen as an effective tool for sustainable agriculture, as their action is based not on increasing the amount of nutrients applied, but on improving the efficiency of their nutrient assimilation by plants and enhancing plant resistance to stress. Hydrolysates obtained from insect larvae (Hermetia illucens L., Tenebrio molitor L., Zophobas morio Fabricius) are characterized by high antioxidant and cytoprotective activity and a rich amino acid composition. The aim of this study was to investigate the effect of larval hydrolysates on the growth and photosynthetic apparatus of beans. Methods. After planting the seeds, they were watered once with hydrolysates of Hermetia illucens, Tenebrio molitor, and Zophobas morio (Zm, Tm, and Hi) at two concentrations each (0.1 % or 0.2 %). The control group was watered with water. The percentage of seed germination, seedling growth, and seedling energy index were determined on the 10th day of germination. On the 15th day, the seedlings were re-treated with hydrolysates. A specific hydrolysate was applied to the roots at concentrations of 0.1 % or 0.05 %, or applied to the leaves (sprayed) at concentrations of 0.1 % or 0.2 %. The growth of seedlings after treatment, the above-ground and below-ground vegetative mass of plants, and the content of chlorophylls a and b and carotenoids in the leaves were determined. Results. Treatment with insect hydrolysates did not significantly affect the overall germination of seeds and the growth of bean seedlings. The seedling energy index showed the stimulating effect of 0.1 % Zophobas morio hydrolysate and the inhibitory effect of 0.1 % T. molitor hydrolysate. Repeated treatment with 0.1 % hydrolysates of Z. morio and H. illucens stimulated bean growth in both types of irrigation. Root and foliar irrigation with insect hydrolysates tended to decrease the content of chlorophyll a and carotenoids and increase the content of chlorophyll b. Only spraying with Z. morio showed a sharp increase in chlorophyll b and a moderate increase in carotenoids, indicating an enhancement of defense mechanisms under such treatments. Conclusions. Among the reagents studied, 0.1 % Zophobas morio hydrolysate performed best, stimulating defense mechanisms at the photosynthetic system level when applied to leaves and growth processes when applied to roots with this reagent. H. illucens hydrolysate stimulated bean growth, while T. molitor had a predominantly neutral or inhibitory effect.