Study of the possible involvement of Azospirillum lectins in the mechanisms of adaptive response of plants exposed to heavy metal salts

Azospirillum, which has the potential to stimulate plant growth, belongs to plant-growth-promoting bacteria. The lectin found on its surface can bind specific carbohydrates and ensures adhesion of the bacteria to the root surface. We examined the effect of the lectins from two strains - A. brasilense Sp7 (epiphytic strain) and A. brasilense Sp245 (endophytic strain) - on the activities of antioxidant enzymes in roots of 4-day-old seedlings of wheat exposed to heavy metals (CoSO4, ZnSO4, Pb(CH3COO)2 and CuSO4). Under all stresses, both lectins increased peroxidase and superoxide dismutase activities and decreased catalase activity, but the periods of effect and the concentrations involved were different. These differences may have been caused by the different structures and carbohydrate specificities of the lectins, which resulted in differences in the interaction with the plant cell surface such differences are of deciding importance for the “switch on” of the subsequent stages. Azospirillum lectins are involved in adaptational changes in wheat seedling roots. This involvement promotes the normal course of metabolism and ensures regulation of the plant- Azospirillum interaction in a wide range of soil and climatic factors.