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| Atmospheric lead (Pb) resulting from modern developing industry enters tea plant leaves and becomes a potential danger threatening people抯 health when they drink tea. To understand the storage capacity of Pb from the air by tea leaves and the possible translocation, we measured by Atomic Absorbance Spectrometer (AAS) Pb contents in leaves, stems and roots of tea seedlings after the two sides of the blade were coated with 180 mg/L C4H12O7Pb?H2O solution for over 6 months and investigated Pb distribution at tissue level by Environmental scanning electron microscopy (ESEM) coupled with energy dispersive X-ray microanalysis (EDXA). The fact of Pb amount in leaves, stems and roots of 132.54 mg/Kg, 82.33 mg/Kg and 30.20 mg/Kg, respectively, suggests an easy Pb uptake and deposition by tea leaves, and phloem translocation. This mobility of Pb in phloem was confirmed by a serious of micro analyses. As the start of Pb uptake, the upper side of the blade lost the cell profiles while the lower kept distinct cell shapes, there was less Pb in lower epidermis near phloem than in the upper epidermis near xylem and less Pb in phloem than in xylem. Accordingly, Pb content in phloem increased from leaf to stem, then to root indicating its translocation via phloem. Relative stable Pb content in xylem tissues of the three organs further supported that the upward transport of Pb was more difficult than the downward. There was no evidence of different amount of Pb in specialized structures like trichomes or storage particles. |
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| Keywords:Camellia sinensis, ESEM, lead, X-ray microanalysis. |
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