Effects Of Foliar Spraying Nano ZnO On Growth And Cadmium Uptake Of Quinoa Seedlings Under Cadmium Toxicity

Quinoa is an important resource for the development of functional food.Quinoa contains a variety of nutrients and has high utilization value.Cadmium(Cd²⁺)is one of the most common heavy metals in farmland.Cd²⁺ is easily absorbed by plants.Excessive Cd²⁺ will not only affect the growth and development of plants,but also endanger human health through the food chain.Previous studies have shown that foliar spraying of zinc（Zn）and silicon（Si）can reduce the absorption of heavy metals in soil by crops and reduce the damage of cadmium to plants.It has not been reported whether foliar spraying of nano zinc oxide（ZnO NPs）can alleviate the damage of cadmium to quinoa seedlings.In this experiment,the effects of Cd²⁺ Stress on the growth of quinoa seedlings were studied by hydroponics.The effects of different concentrations of ZnO NPs on the growth of quinoa seedlings under Cd²⁺ stress were studied by applying Cd²⁺ Stress on potted soil and spraying ZnO NPs on leaves.Objective to explore the physiological mechanism of foliar spraying appropriate amount of ZnO NPs to alleviate the damage of Cd²⁺ on the growth of quinoa seedlings,so as to provide a theoretical basis for the application of ZnO NPs in quinoa production.The main results are as follows:1.Cd²⁺ inhibited the growth of quinoa seedlings.With the increase of Cd²⁺ concentration,the plant height,root length,dry and fresh weight of quinoa seedlings decreased gradually,and the photosynthesis of quinoa leaves was inhibited,which showed that the photosynthetic index and photosynthetic pigment content of leaves decreased;Cd²⁺ Stress destroyed the antioxidant system of quinoa,decreased the activities of antioxidant enzymes SOD,pod and cat,and decreased the content of soluble protein.2.Spraying appropriate concentration of ZnO NPs solution can effectively reduce the damage of Cd²⁺Stress on the growth and development of quinoa.The plant height,aboveground fresh weight,underground fresh weight,aboveground dry weight and underground dry weight of quinoa under 5 mg/kg Cd²⁺ and 20mg/L ZnO NPs treatments were 17.2%,31.67%,46.46%,28.6% and 31.88% higher than those of 5 mg/kg Cd²⁺ treatment,respectively,and the photosynthetic rate of seedlings was 55.2% higher than that of 5 mg/kg Cd²⁺ treatment.Foliar spraying with appropriate concentration of ZnO NPs may alleviate the damage of Cd²⁺ to the growth and development of quinoa through antagonizing the absorption of Cd²⁺ by ZnO NPs,reducing the oxidative stress damage of Cd²⁺ to the seedlings,and then enhancing the photosynthesis of seedlings.