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《Acta Photophysiologica Sinica》 2002-03
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The Distribution of Pb and Pb-stressed Relative Proteins in Pb-polluted Phragmites australis Seedlings

JIANG Xing-Yu ZHAO Ke-Fu (Institute of Plant Stress, Shandong Normal University, Jinan 250014)  
The Pb distributions of different organs and subcellular compartments, the relative abundance of different chemical forms of Pb as well as Pb-stressed relative proteins in Phragmites australis seedlings were determined after the seedlings were exposed to Pb(NO 3) 2 10 mmol/L solution for 7 d. The atomic absorption spectrophotometric analysis revealed that the levels of Pb in roots, rhizomes, stems and leaves of the seedlings increased significantly in decreasing order in the presence of Pb 2+ in the culture solution (Table 1). In order to study Pb compartmentalization within the root cells of P. australis seedlings polluted by Pb, transmission electron microscopy and X-ray energy spectrum microanalysis had been applied to measure the levels of Pb in various parts of root cortex cells of P. australis seedlings. The results showed that Pb distribution sequence is: intercellular spacecell wallvacuolecytoplasm (Table 2). The study of Pb forms using sequential extraction method showed that the extraction ratio of Pb extracted respectively was different from different extraction media, of which less active HAc-extracted and HCl extracted fractions were the main forms in roots and in leaves (Table 3). By gel filtration, some Pb-binding complexes were formed in roots and leaves of P. australis seedlings polluted by Pb. In addition, Pb stress also induced a new protein with a mol. wt. of 30 000 and led to the disappearance of a protein with a mol. wt. of 72 000 (Fig.1). All results suggest that the possible defense mechanism in P. australis involves Pb accumulation in root; formation of insoluble complexes; concentration in apoplast and vacuole by compartmentalization; the binding with Pb of specific proteins. In addition, P. australis can synthesize a new protein which might function to protect P. australis cell from Pb stress.
【Fund】: 国家重点基础研究发展规划项目 (G19990 1170 0 );; 环境水化学国家重点实验室开放基金资助
【CateGory Index】: Q945.78
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