Effect Of Graphene Oxide On Growth Of Plant

Nanomaterials have been widely used in a variety of areas including electronics,mechanics,energy,and biomedicine due to their unique properties.The inevitable release of nanomaterials into water and soil may affect the quality and yield of plant.Their accumulation in plants could lead to problems with food safety and human health.“Plant Nan Omics”is an emerging topic in agricultural research that explores the potential effect of nanomaterials on plant growth.Graphene oxide?GO?is an important graphene derivative with excellent physicochemical properties,that broaden its applications in biology,medicine and environmental remediation.In recent years,GO has shown great potential for the applications of slow-release fertilizers,bactericide and insecticides.It is essential to explore the health and environmental risks associated with their application in agriculture to ensure their safe use and social acceptance.In this thesis,GO and plants were applied in hydroponic and soil cultures.The effect of GO on plants were investigated and its underlying mechanisms were clarified.Cut roses were cultivated in different concentrations of GO.The results showed GO-concentration dependent extension of rose vase life,and suggested that higher GO dosages caused GO blockage at the stem end,and low doses of GO effectively prevented microbial blockage and increased the water uptake,resulting in higher water relations of cut roses.Low water stress reduced the accumulation of reactive oxygen species?ROS?,and thus decreased the cell death.Therefore,optimal doses of GO could be used to extend the vase life and improve the visible ornamental value of cut roses due to its antimicrobial property.GO and plants were applied in soil system.GO could pro mote the germination and growth of plants due to its hydrophilic nature and water-transport properties.The oxygen-containing functional groups of GO collected water,and the hydrophobic sp² domains transported water to the seeds to accelerate the germination of plants.The strong interaction between GO and the surfaces of soil grains stabilized GO in the soil and prevented dissipation of GO.In addition,no GO was detected either on the surface or inside the cells of plants.This finding confirmed that GO was not phytotoxic.Cadmium?Cd?contaminated soil and rice were employed to investigate the effect of GO on the adsorption of heavy metals and the indirect toxicity of GO to plants.The results showed that GO promoted Cd²⁺uptake by rice in the soil system.The oxygen-rich functional groups and the large specific surface area of single-layer GO resulted in strong Cd²⁺adsorption with a maximum adsorption capacity of 265.8 mg/g.The carboxyl groups at the edge of GO acted as electron donors to adsorb Cd²⁺by electrostatic interaction.The strong Cd²⁺adsorption capacity of GO used in this study significantly changed the existing forms of Cd in the soil.In particular,GO converted the inorganic-bound form Cd that was not readily absorbed by plants into the exchangeable form that was more available for plant absorption.As a result,Cd content in rice seedlings was increased by 12.5%with the application of GO.Therefore,it was concluded that GO exhibited indirect toxicity to plants in heavy metal-enriched soil.