Silver Nanocomposite Based on Synthetic Humic Substances as Highly Efficient Plant Growth Stimulants
Authors: Litvin V.     A. , Zaporozhets A.  V. , Ozivska I.  O. 
Published: September 2022

Introduction. Nanotechnology have positive impact in improving many sectors of economy including agriculture. Silver nanoparticles (AgNPs) have been implicated nowadays to enhance seed germination, plant growth, improvement of photosynthetic quantum efficiency and as antimicrobial agents to manage plant diseases.Despite the known growth-stimulating activity of preparations of humic substances and silver nanoparticles, there is currently no information on the effect on growth processes of composites containing silver nanoparticles encapsulated in macromolecules from synthetic humic substances. It is expected that such combined nanopreparations have enhanced and complementary properties of a metal core and a shell of humic synthetic substances.Purpose. The aim of this study was to investigate the growth-stimulating activity of silver nanocomposites based on synthetic humic substances derived from quercetin, and to determine the range of active concentrations in the process of germination of wheat seeds.Methods. The received silver nanoparticles are characterized by UV–visible spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy and transmission electron microscopy (TEM). To study the growth-stimulating activity of synthetic humic substances and silver nanocomposites, a series of solutions was prepared on their basis by dilution with a logarithmic decrease in concentration from 1·10–1 to 4·10-16%.Result. Nanobiocomposites containing silver nanoparticles and synthetic humic substances were synthesized in the reaction of reduction of silver ions with synthetic humic substances obtained in laboratory conditions from quercetin.Preference of synthetic humic substances over natural humic substances is determined by a standardization problem resolution due to the strict control of conditions of the HS formation that expands the areas of application of the silver nanoparticles made on their basis. The high crystallinity of nanobiocomposites with fcc phase is evident from XRD patterns. The TEM results show that the silver nanoparticles are spherical in shape with average size about 9.6 nm. The FTIR spectroscopic study confirmed that the synthetic humic substances have ability to perform dual functions of reduction and stabilization of silver nanoparticles.The growth-promoting activity of synthetic humic substances and silver nanocomposites based on them was studied on the example of germination of wheat seeds of the variety "Zolotokosa" according to standard procedures. It is established that aqueous solutions of synthetic humic substances and silver 54 Серія «Біологічні науки», 202 2nanocomposites based on them in a wide range of concentrations have a complex effect on the growth and development of wheat seeds. It is shown that seed germination increases (by 2–40%) and the length of the main root (by 9–100%) of wheat germ increases. It should be noted that synthetic humic substances and silver nanocomposites based on them to a greater extent stimulate root growth, which is important for agriculture in arid areas. The ranges of effective concentrations of solutions of the studied drugs show the maximum total stimulating activity (by the number of germinated seeds and the length of the main root compared to the control) during germination of wheat seeds for synthetic humic substances and for silver nanocomposite - 10-10-10-4%. Stimulation of root growth by silver nanocomposites based on synthetic humic substances in most concentrations exceeds the effect of the original humic substances.Originality. The established activity of synthetic humic substances and silver nanocomposites based on them is a prerequisite for the further development of highly effective growth-stimulating preparations of a new generation.Conclusion. It has been established that silver nanocomposites based on synthetic humic substances exhibit highly effective growth-stimulating activity. The ranges of active concentrations of the studied preparations demonstrate the optimal stimulating activity for synthetic humic substances and silver nanocomposite based on them by the number of germinated seeds 1·10–10–1·10–4 %, by the length of the main roots compared to the control - 1· 10-12-1· 10-4%. The established activity of synthetic humic substances and silver nanocomposites based on them is a prerequisite for the further development of highly effective growth-stimulating preparations of a new generation.Key words: synthetic humic substances; silver nanocomposites; growth-promoting activity; wheat