GREEN SYNTHESIS OF COMMON SILICA AND NANO SILICA AND THEIR IMPACT ON LEAD TOXICITY IN WHEAT

Abstract

Lead (Pb) is an unimprtant toxic heavy metal that decreases agricultural productivity, by impacting the physiological and biochemical properties of various crops. Lead toxicity causes wheat productivity to plunder, by inducing oxidative stress in wheat. Wheat is an essential part of human diet. It is a nesessary food for 50% of the global population. Silicon is known to counter the adverse effcts of heavy metal toxicity. The aim of this study was to synthesize common silica and nanosilica from rice husk and, to observe their effect on wheat grown under lead contaminated soil. Rice husk was leached with hydrochloric acid, and then rinsed with de-ionized water and after heating it in muffle furnace at 700 °C, silica particles of nano size were obtained. Different heating cycles were employed on rice husk to synthesize common silica particles. Wheat was grown in pots containing 5 kg of lead contaminated soil to observe the impacts of silica nanoparticles. Three different levels of common silica and nano-silica particles (0, 300 and 500 mg/kg) were applied in the soil before one week of wheat sowing. The lowest chlorophyll content, root weight, shoot weight and husk weight were observed in the control plants while the highest lead concentrations in shoots, roots, and grains were observed in the control plants. Common silica and nano-silica particles improved wheat growth by increasing root, shoot and grain weight, and counter oxidative stress in wheat by lowering hydrogen peroxide, electrolyte leakage and malondialdehyde content in leaves. When compared with control, nano-silica treatment reduced Pb concentration in wheat root, shoot and grain. This study indicates that silica treatment improves the growth of wheat in a lead contaminated soil by restricting its entry into wheat. NPs silica are more efficient in countering heavy metal toxicity in wheat than bulk silica particles.