Study of the effects of humate and active silicon form based biostimulants on wheat drought tolerance

Abstract

One of the factors detrimentally affecting agricultural production is drought frequency increase as a result of global climate change. Some studies report the ability of silicon-based and humic biostimulants to enhance plant resistance to water shortage while the underlying mechanisms remain insufficiently investigated. The goal of the current greenhouse experiment was comparative research of the effect of three silicon-based biostimulants and two humic preparations on growth and development of wheat plants grown under optimal irrigation and limited irrigation (50% of the optimum). All tested biostimulants increased underground and aboveground biomass for both irrigation modes. But the impact was more pronounced when water supply was scarce implying the ability of preparations to enhance resistance of wheat plants to drought. The treatment with monosilicic acid was the most efficient in terms of plant growth. Under water scarcity, silicon-based biostimulants had higher beneficial impact than that of humic preparations. Both types of biostimulants increased the contents of chlorophyll a and b while humic preparations demonstrated higher efficiency as compared to silicon-based preparations. Under limited irrigation, humic biostimulants had greater impact on chlorophyll b than chlorophyll a, thus resulting in decreased chlorophyll a/b ratio. Decline in this parameter supposes increased plant resistance to unfavorable growth conditions. Silicon-based biostimulants significantly reduced thiobarbituric acid reactive substances which indicated decreased lipid peroxidation level and improved antioxidant activity. Silicon-based biostimulants provided enhanced stress-ferment activities: superoxide dismutase, glutathione reductase, and guaiacol peroxidase. The activities of stress-ferments in plants treated with humic preparations increased slightly. Both types of biostimulants promoted wheat resistance to water deficiency, however the underlying mechanisms were different.