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Toxicity And Mechanism Of Silver Nanoparticles To Lettuce(Lactuca Sativa L.)under Foliar And Root Exposure Pathways

Posted on:2021-02-06Degree:MasterType:Thesis
Country:ChinaCandidate:W Q LiFull Text:PDF
GTID:2370330614453949Subject:Environmental Engineering
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Silver nanoparticles?AgNPs?have found widespread application in consumer products,medicine,technology etc.,amongst others due to their strong antimicrobial properties.Their growing use and production inevitably lead to an increased release into the environment and enter the soil through multiple routes?such as,via biosolids fertilization,irrigation and atmospheric deposition etc.?.Soil is an important part of terrestrial ecosystem,and the buildup of AgNPs in soil is bound to affect the safety of terrestrial ecosystems.Since plants are the primary producers of terrestrial ecosystems and the foundation of terrestrial ecosystem food chains,the issues of the uptake,accumulation and transformation of AgNPs in planta are worthy further study.NPs accumulate in plants via either root or foliar uptake.Up to date,AgNPs uptake by root has been extensively investigated,whereas studies on foliar uptake of NPs are lagging behind.Furthermore,AgNPs are sprayed directly on crop plants as an antimicrobial agent used in agriculture.Studies on the foliar exposure pathway are therefore necessary for a comprehensive risk assessment of nanomaterials,especially in agricultural soils.In this research we investigated the phytotoxicity?plant biomass and oxidative damages?,uptake,and internal fate?i,e.,Ag subcellular partitioning and chemical forms?of AgNPs in lettuce following foliar versus root exposure.It is expected that the relationship between exposure pathways,the chemical speciation and phytotoxicity of AgNPs will be clarified.The results will provide the fundamental basis for the evaluation and control of AgNPs environmental risks,and will be critical to food safety.The main conclusions of this research are as follows:?1?The exposure pathway significantly affected the accumulation and phytotoxicity of AgNPs to lettuce.At the same AgNPs exposure concentrations,root exposure led to more deleterious effects than foliar exposure as evidenced by a larger extent of reduced plant biomass?75.9%biomass reduction and 1.7 times more reduction than in foliar exposure?,elevated oxidative damage(H2O2:1038.7±131.1?mol·g-1vs.570.0±71.1?mol·g-1;MDA:6.7±0.7?mol·g-1 vs.4.2±0.6?mol·g-1),as well as a higher amount of ultrastructural injuries detected by TEM and AFM,despite foliar exposure leading to 2.6-7.6 times more Ag bioaccumulation.?2?The exposure pathway significantly affected the subcellular distribution and chemical forms of Ag in lettuce.Following foliar exposure,high Ag in biologically detoxified metals pool?29.2–53.0%by foliar exposure vs.12.8–45.4%by root exposure?and low Ag proportion in inorganic form?6.1e11.9%vs.14.1–19.8%?potentially associated with AgNPs tolerance.?3?Ag-containing NPs were detected in lettuce leaves regardless of exposure pathways and Ag species?NPs vs.dissolved Ag+?,and these in planta NPs?24.8-38.6nm?were significantly larger than the pristine AgNPs?16.5±0.2 nm?,suggesting possible transformation and/or aggregation of AgNPs in planta.
Keywords/Search Tags:Silver nanoparticles, Subcellular partitioning, Chemical forms, Foliar exposure, Root exposure
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