Yunosheva O. Allelopathic Features of Lavandula L. Genus Species Plants Under Forest Steppe Conditions

The allelopathic activity of plant exometabolites in species of the Lavandula L. genus during ontogenesis under the agroecological conditions of the forest steppe region of Ukraine was studied. Allelopathic activity of plant organs was found to be from high to low in the following order: leaves ? inflorescences ? roots (for water-soluble secretions), inflorescences ? leaves ? roots (for volatile secretions). The highest allelopathic effect was observed in the flowering phase. Garden cress was determined to have the greatest sensitivity to lavender plant secretions. The allelopathic activity of soil under lavender is characterized by a low level of toxicity with a maximum bioassay result of 17.5% for water-soluble and 25.9% for volatile compounds. The toxicity of the lavender rhizosphere was considerably lower under forest steppe conditions compared to that of plants grown in the southern regions of Ukraine. The biological activity of lavender plant residues was analyzed and determined that their addition to the soil has a positive effect on the growth and development of spring rape, winter wheat and marigold plants. The analysis of the functional structure of microbial cenosis in the rhizosphere of lavender and lavandin shows a decreased quantity of micromicetes and an increase in the amount of spore forming bacteria. The effect of Lavandula L. essential oils on phytopathogenic bacteria and micromycetes has been studied. The species-specific effect of the experimental plants' biologically active compounds on seed germination of cultivated and segetal plants has been established. The positive influence of silicon-containing natural minerals on the growth and development of the experimental plant species and the structural and functional organization of soil ecosystems has been shown.