Effects Of Application ZnO NPs On Potato Growth,Zinc Absorption And Soil Microorganisms

ZnO NPs have unique physical and chemical properties and are considered to be a potential material for human Zndeficiency.However,information about food safety and environmental impacts of ZnO NPs exposure are limited,and it is important to know the effects of ZnO NPs on Znbiofortification and environmental risks.Potato occupies an important position in food production in China.The tubers are contact with ZnO NPs in soil directly during growth.The possible impacts are not clear yet.In this study,potato was used as test crop,and two experiments were set up:sand cultural experiment and soil cultural experiment.There were 7 treatments in the sand cultural experiment,including Zinc-free?CK?,ZnO NPs 10,50,200,500,800 mg L^-1and ZnSO₄50 mg L^-1,and 9 treatments in soil cultural experiments,Zinc-free?CK?,soil application of ZnO NPs 10,50,200,500,800 mg kg^-1,soil application of ZnSO₄50 mg kg^-1,spraying ZnO NPs 50 mg L^-1and spraying ZnSO₄50 mg L^-1at the budding period.To explore the effects of ZnO NPs on potato growth,yield,Znabsorption and soil microorganisms,and provide basis for application security and environmental risks of ZnO NPs in agriculture.The main findings are as follows:1. ZnO NPs showed a tendency of promoting growth of potato seedlings at low concentrations and inhibiting growth at high concentrations at sand culture,which were reflected in the inhibitions on seedling biomass,root activity,synthesis of photosynthetic pigments and the changes of antioxidant enzyme activitives when the concentration above200 mg L^-1.Soil adsorption alleviated the toxicity of ZnO NPs.ZnO NPs showed slight promotion or no significant effects on the growth of potato.2. All of Zn treatments showed no significant effects on tuber yield,while due to Zntreatments reduced the number of tubers,and tuber yield in some treatments were lower than control,and the average single potato weight was higher than control.Total weight and number of tubers were lowest when ZnO NPs at 800 mg kg^-1,which were 87.09%and55.66%of control,respectively.ZnO NPs contributed to the expansion of tubers,increased the rate of large potatoes and reduced the rate of small potatoes compared to control,the optimum concentration is 200 mg kg^-1.3. ZnO NPs increased Zn content of potato tissues under both sand and soil culture significantly,and continued to increase with the increase of concentration.Zncontents in mature potato plants were stem>stolon>root>leaf>tuber,Zncontent in tuber was increased by 8.07-38.46 mg kg^-1compared with control under soil culture at different concentrations of ZnO NPs.XRD spectra of Znspecies in potato tissues treated with ZnO NPs at 50 mg kg^-1showed that there were no ZnO NPs in potato tissues.Spraying ZnO NPs and ZnSO₄50 mg L^-1for one time could not increase Zncontent of tubers effectively.4. ZnO NPs had different effects on the absorption of nutrients in potato seedlings and tubers.ZnO NPs had no significant effect on nitrogen content at sand culture conditions,but reduced phosphorus and potassium content at high concentrations,while no significant effects on all macroelements in tubers in soil culture.In sand culture,iron content was not significantly affected,copper and manganese content increased in aboveground part,while decreased in underground part.In soil culture,ZnO NPs at medium concentrations increased the copper content in tubers,but had no significant effect on iron and manganese content.5. Addition of ZnO NPs did not change original dominant species of bacterial and fungi communities in soil after potato planting,but it changed the relative percentage of species.During the cultivated time of this experiment,the bacterial community was more affected than fungi.Effects of ZnO NPs on bacterial community abundance,diversity at high concentration is greater than low concentration.Gemmatimonadetes,Actinomycetes,and Chloroflexi are more sensitive to ZnO NPs,while Proteobacteria and Bacteroides are more tolerant than others.For fungi,ZnO NPs increased the abundance of fungi communities and decreased the diversity,while ZnSO₄had an inhibitory effect on both abundance and diversity,Ascomycota and Glomeromycota changed significantly.6. ZnO NPs showed the similar effects on potato growth,tuber yield with ZnSO₄at the same concentration and there is no toxic effect was found different from ZnSO₄.Zncontents are affected by the cultivation time and culture.Zncontent of potato seedlings at the treatment of ZnSO₄in sand culture is higher than that of ZnO NPs at the same concentration,while Zncontents of tubers are similar in the soil culture.In summary,ZnO NPs showed a dose-response relationship to the growth of potato seedlings at sand culture,there were promotions at low concentrations and inhibitions at high concentrations,and the complex soil composition alleviated the toxic effects of high concentration ZnO NPs.ZnO NPs could increase Zncontent of potato tubers effectively,and there is no nano-specific risks were found.Pros and cons of effects of ZnO NPs on soil microbial community need to be further explored.These findings help us to further understand the potential Zn-biofortification and environmental risks of ZnO NPs.