Variation And Mechanism In Uptake And Translocation Of Perfluorooctanoic Acid (PFOA) Among Lettuce(lactuca Sativa L.)cultivars Grown In PFOA-polluted Soils

Perfluorinated compounds(PFCs),the typical persistent organic pollutants which has a strong toxic effect and widely used in chemical,pharmaceutical(including pesticide),textile and other industrial as well as agricultural area,were extensively detected in soil.Since it threatened the quality and safety of agricultural products and human health seriously,the strategy of screening safe varieties with low accumulation of pollutants in crops arouses growing concern these years.Therefore,high-and low-PFOA cultivars were selected as the object of the study from 20 varieties of lettuces widely planted in China via soil pot experiment.And through the absorption kinetics experiment,channel inhibitor experiment,split root experiment,root morphology scanning,root distribution analysis,and inter subcellular,rhizosphere DOC content and PFOA morphology analysis of physiological and biochemical control factors,the mechanism of discrepancy between high-and low-PFOA cultivars was discussed.The main results of this thesis are as follows.(1)The discrepancy in PFOA uptake and accumulation among different cultivars were significant,and it was stable under various PFOA exposure conditions.Three low-PFOA cultivars were obtained,which belong to looseleaf lettuce subtype.Due to their large biomass and low PFOA content in shoots(edible part),they could ensure food safety even if they were grown in highly polluted soil(1 mg/kg).(2)The absorption process of PFOA in the roots of high-PFOA cultivar was an active transport process involving aquaporin and anion channels,while the process of absorption of low-PFOA cultivar was mainly passive,and the former is better than the latter in absorbing PFOA.When absorbed into the root system of lettuce,the high accumulation cultivar showed higher translocation of PFOA than the low accumulation cultivar,and the distribution of PFOA in the cell wall and organelle was lower than that in the latter,which was beneficial to the transport of PFOA to shoot,which showed higher properties of PFOA absorption and transport.(3)The root biomass(root elongation,root volume,root surface area,etc.)and the root structure complexity(root tip number,root cross number,root bifurcation number,etc.)of high-PFOA cultivar were significantly higher than the low-PFOA one under blank condition and PFOA exposure condition.The content of soluble organic carbon in rhizosphere was also significantly higher than that of low accumulation cultivar,which resulted in more desorption of PFOA in rhizosphere,and was beneficial to its absorption of PFOA,thus showing a high accumulation.