| Tea plant (Camellia sinensis (L.) O. Kuntze) is a typical plant of accumulating andtolerating fluoride and aluminum. Tea is one of the three major beverage plants in theworld, the relationship between fluoride by drinking tea and human health have attractedmore attention in recent years. Fluoride, a kind of environmental pollutants, is easy to beabsorbed by soil and presented in the soil. This paper mainly made some researches onchemical forms change of exogenous water solution fluoride and bioavailability in teagarden soil, kinetic characteristics of solution fluoride uptake of the tea plant, fluorideaccumulation and its subcellular distribution and chemical form of fluoride and its effecton XPS analysis of tea plant leaf. The main contents were summarized as fellowed:1. Pot experiments and the sequential extraction method were conducted to study thechemical forms change of exogenous water solution fluoride in tea garden soil and theircontribution to fluoride accumulation of tea plant. The results showed that backgroundconcentration of all chemical forms fluoride had little changes with time treatment, whichwas in a relatively stable state. The exogenous water solution fluoride adding to the soilswas rapidly transformed to other fractions. Under the10mg kg-1fluoride treatment, theconcentration of water solution fluoride increased firstly and then decreased with timetreatment, the concentration of organic matter fluoride and Fe/Mn oxides fluoridedecreased, the concentration of exchange fluoride was no differences before and aftertreatment(p>0.05), and the concentration of residual fluoride was in a relatively stable state.Under the200mg kg-1fluoride treatment, the concentration of water solution fluoride,Fe/Mn oxides fluoride and organic matter fluoride decreased with time treatment, theconcentration of exchange fluoride increased firstly and then decreased, showed nodifferences before and after treatment(p>0.05), and the concentration of residual fluorideincreased, with some differences compared with10mg kg-1fluoride treatment. Theconcentration of total fluoride of root, stem and leaf had significant differences under0-10mg kg-1fluoride treatment(p<0.05), while showed no differences from10to100mg kg-1fluoride treatment(p>0.05). Step regression analysis suggested the contribution of allchemical forms fluoride to the concentration of water solution fluoride and total fluoride ofroot, stem and leaf had some differences, there was a remarkable regression relationshipamong the content of total fluoride in leaf and water solution fluoride, organic matterfluoride, Fe/Mn oxides fluoride and residual fluoride in soil, however, not significant for water solution fluoride of leaf.2. Solution culture experiments were conducted to study the kinetic characteristics ofsolution fluoride uptake by tea plant under different F concentration and elapsed-time.The response of tea plant growth to F was also studied. The results showed that, thetolerance to F of tea plant depended on the species, and F(≤10mg L-1) could promotebiomass accumulation and root growth, but high F(≥50mg L-1) was bad for tea growth.F concentration in leaves and stems increased linearly along with treatment time at1mg L-1F in nutrient solution(R2stem=0.9164，R2leaf=0.9706), while F concentrations inroot has significantly differences. Under10mg L-1F treatments, F concentrations inroots, stems and leaves increased linearly along with time, and then reached amaximum on32d. The kinetic characteristics of solution fluoride uptake by the teaplant under low F treatment(0.1-10mg L-1) matched the model of Michaelis-Menten,which was an active uptake. Under high F(50-100mg L-1) concentration, F uptakeshowed a passive process, which lead to a sharp increase of F concentration in rootsand stems. The F concentration of leaves reached saturation when F supply level was5mg L-1. The kinetic curve of F uptake fitted linear-quadratic (LQ) model: fast linearuptake and slow saturation uptake. The absorption rate and transportation rate of F bytea plant increased linearly along with F treatment concentrations.3. Solution culture and differential centrifugation were conducted to study thecharacteristics of F accumulation and its subcellular distribution of Pingyangtezao,Wuniuzao and Fuzao No.2, with comparison of the differences between varieties. Fconcentration in root, stem and leaf of three kinds of tea plants increased with F treatment,under0-10mg·L-1F treatment, the ground part of fluoride content was greater than theroot(Translation correlation>1) and56%of F was distributed overground part. Except forthe control, most fluoride of leaf was distributed in cell walland soluble fraction(76.84%-91.58%), which showed the same performance of root (53.24%-80.35%). Ftreatment generally increased the percentage of cell wall and soluble fraction, butdecreased that of cell organelle. Under F treatment, the change tendency of F concentrationof subcellular fractions of leaf of Pingyangtezao and Wuniuzao ranked in the followingorder: cell wall> soluble fraction> cell organelle, while soluble fraction> cell wall> cellorganelle for Fuzao No.2. Under low F (0-5mg·L-1) treatment, the change tendency of Fconcentration of subcellular fractions of root of three kinds of tea plants ranked in thefollowing order: cell organelle≥cell wall> soluble fraction, while cell wall> soluble fraction≥cell organelle for high F (10-50mg·L-1) treatment. Translation correlation,percentage of F for overground part and F subcellular distribution in root and leafsuggested tea plant was of strong upward transportation capacity. The subcellulardistribution of F in leaves and roots were related with tea species and solution F treatment,and so did the correlation between the concentration of T-F and subcellular fractions in leaf,with some differences, but no in root. Cell wall and soluble fraction were the main storagesites under high F treatment.4. X-ray photoelectron spectroscopy(XPS) was applied to analyze the chemical form offluoride and its the effect on XPS analysis of tea plant leaf. It was detected that the leafsurface was made up of mainly2elements: C and O, some Si, N and Al, and a smallamount of P and Ca in the adaxial surface. Under fluoride treatment, the content of Cincreased, and O decreased in the abaxial surface, which was contrast to the adaxial surfaceperformance. Aluminium (Al)in the abaxial surface showed the trend to be transported tothe adaxial surface, the content of N in leaf surface decreased, and its nitrogen fixationability reduced. Fluoride treatment made cuticle thinner, cutinized layer thicker, muchorganic acid secreted by surface, and oxidation state more active of the adaxial surface,both cuticle and cutinized layer became thicker, less organic acid, and reduced oxidationstate of abaxial surface. Fluoride treatment caused the content of protein in leaf surfacedecreased, which was not good for keeping moisture of the leaf surface. O2/O1>1, andfluoride treatment made it decreased. Fluoride mainly existed as AlF3in adaxial surface,maybe with a small amount of MgF2or CaF2, but existed as MgF2in abaxial surface. |
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