Effects of humic substances on seed germination of wheat under the influence of heavy metal
Introduction. The rapid development of industry in recent decades has caused global pollution, including heavy metals. Of particular danger is the accumulation of heavy metals in plants widely cultivated in crop production practices, such as wheat. Among growth-promoting and remedying drugs, compounds of natural origin — humic substances — deserve special attention. Currently, around the world there is an increased interest in humic substances, the technologies for their production are being improved, and the raw material base is expanding, in which all new types of raw materials are involved. Of particular interest are synthetic humic substances, which are obtained from low molecular weight phenolic precursors. Strict control of the synthesis conditions allows obtaining a product with standardized properties, which is one of the advantages over natural humic substances. In addition, it is assumed that the nature of the low molecular weight phenolic precursor affects the biological activity of the final product.
Purpose. The aim of our study was to study the effect of humic substances of various origins (a complex preparation of natural humic substances and synthetic fulvic acids from catechol) on the germination and morphological characteristics of wheat under the influence of heavy metals (Cu2+).
Methods. During the study, laboratory, accounting, analytical and mathematical-statistical methods were used.
Result. A comparative study of the effect of a complex preparation of natural humic substances and synthetic fulvic acids from catechol on the germination of wheat seeds shows their stimulating effect compared to the control by 11.2% and 8.2%, respectively. The presence in the nutrient solution of Cu2+ ions at the levels of 0.5, 1 and 5 MPC contributed to the increase of germination energy and germination of seeds in all experiments. The types of humic substances investigated intensify the growth processes in green shoots of wheat. Compared to the control, their length increased by 18.9 - 35.1%. In addition, these substances inhibit the negative effects of Cu2+ ions even at the level of 5 MPC. Aqueous solutions of Cu2+ ions have been found to stimulate the formation of primary roots in wheat. At the same time, ions of this heavy metal have a negative effect on root growth, reducing their length by 7.5 times compared to the control. The total length of all roots in wheat plants under the action of different types of humic substances exceeded the control values by 42 - 50%. At the same time, these substances significantly improved root growth when Cu2+ ions were present in the nutrient solution. The presence of Cu2+ ions in the solution adversely affected the crude mass of green shoots and roots in the studied wheat plants. However, humic substances improved these indicators compared to the control by 26.8 - 43.3%, which indicates their detoxifying effect.
Conclusion. Thus, the treatment of wheat seeds with the studied preparations of natural humic substances and synthetic fulvic acids from catechol activates biological and physiological processes in the seed, thereby affecting the vital activity of the plant at the initial stage of development, affects the formation of additional primary roots and the growth of wheat seedlings. The studied preparations have a positive effect on the accumulation of fresh mass of wheat seedlings, and allow to obtain friendly and uniform seedlings. In addition, under conditions of soil pollution with Cu2+ ions, various types of humic preparations exhibit phytoprotective properties.
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