The effect of zinc oxide nanoparticles bioaccumulation in seedlings on growth and development of vetch (Vicia sativa)

Abstract

This paper shows the possibility of accumulation of zinc nanoparticles in vetch seedlings (Vicia sativa) and their influence on the morpho-physiological and biochemical parameters of plant development when germinating seeds on a gel-like cultivation medium. The stability of nanoparticles in this medium is shown, which is an important parameter for the validity and reliability of the results obtained. When using various methods of electron microscopy, transmission (TEM) and scanning (SEM), the adhesion of nanoparticles on the surface of plants and their accumulation in apexes and roots of seedlings is shown. The physical-chemical characteristics of zinc oxide have been revealed: the composition and morphology of the particles. The reasons for zinc oxide accumulation are apparently the following ones: high adhesion to surfaces of living systems, negative charge, nanoparticle size, solubility and sustainable formation of agglomerates. For zinc oxide nanoparticles, changes in the activities of peroxidase and superoxide dismutase enzymes are more than 30% with a concentration of nanoparticles above 10.0 g/t, which proves slower plant growth. Consequently, a significant deviation of parameters of the biochemical status of plants from the norm can serve as a signal of a toxic effect of nanoparticles. The effect of zinc oxide nanoparticles on the activity of vetch phytohormones has been studied. In the concentration range of 0.001-1.0 g/t, the content of indole acetic acid (IAA) under the action of nanoparticles increases, and the energy efficiency of plant respiration increases, which leads to large changes in the activity of various enzymic reactions and positive dynamics of growth and development of vetch seedlings. When concentrations increase above 1.0 g/t, IAA values decrease. Biologically active nanoparticles, acting on the level of phytohormones, can influence the state of bio membranes and indirectly act as a regulator of protein synthesising cells of plants, which leads, depending on the concentration of nanoparticles, to growth or inhibition of the development of living systems. The concentration of zinc oxide nanoparticles of 10 g/t of seeds, when all morpho-physiological and biological parameters indicate some inhibition of vetch growth and development, is particularly dangerous.