IMPACT OF REDUCED GRAPHENE OXIDE ON MITIGATING LEAD STRESS IN WHEAT PLANTS: MORPHOLOGICAL AND PHYSIOLOGICAL RESPONSES

Abstract

Rapid global industrialization and population increase have increased the risk of heavy metals accumulation in plant body. Lead (Pb) is regarded as the 2nd most toxic heavy metal causing toxicity in plants, animals as well as in human beings. Pb can accumulate in plant tissues and disrupt the morphological, biochemical, and physiological processes of plants, which in turn results in substantial variation in plant functions. In this study, Graphene oxide was synthesized through graphite oxidation by Hummers methods in a stepwise manner and was greenly reduced through the use of Tecoma stans plant leaves extract. Uv-spectroscopy, FTIR, XRD, Zeta potential, and SEM were done for the characterization of reduced graphene oxide (rGO) nanoparticles. In the current study, a pot experiment was conducted in which different concentrations (15, 30, 60, 120 mg/L) of rGO were applied. Three different concentrations (300, 500,700 mg/L) of Pb stress were applied. To observe the mitigative effects of rGO, 30 mg/L of rGO and 700 mg/L of Pb were used in combination. Changes in morphological and biochemical characteristics of wheat plants were noted for both Pb stress and rGO treatments. Pb was found to inhibit the morphological and biochemical characteristics of plants. rGO, alone as well as in combination with Pb stress, were found to enhance root/shoot growth, and biomass of the plants over control treatment. rGO was found to increase the chlorophyll content of wheat plants, while Pb was found to reduce it. In a combined treatment of rGO and Pb, an increase in chlorophyll content was observed in comparison to control and Pb stress plants. Under Pb stress conditions antioxidant enzyme activities like SOD and CAT were found to decrease in comparison to control treatment while they were greatly enhanced by rGO NPs alone and in combination with Pb. Enhancement in the activities of POD and APX were found for both rGO NPs and Pb separately and in combination as compared to the control. The current findings revealed that greenly reduced graphene oxide NPs can effectively promote growth in wheat plants under the stress conditions of Pb by elevating the chlorophyll content of leaves, reducing the Pb uptake, and suppressing ROS produced due to Pb toxicity. The application and use of graphene oxide for the improvement of plant growth is dose-dependent and may vary from species to species in plants.