Chemical Composition of Root and Stem Saps in Relation to Cadmium Resistance and Accumulation in Brassica parachinensis

作     者：WU Qi-Tang XU Zhao-Li YE Hui J. W. C. WONG WU Qi-Tang, XU Zhao-Li, YE Hui and J. W. C. WONG College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642 (China). Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China)

作者机构：College of Natural Resources and Environment South China Agricultural University Guangzhou 510642 （China） Department of Biology Hong Kong Baptist University Kowloon Tong Hong Kong SAR （China） 

出 版 物：《Pedosphere》 (土壤圈（英文版）)

年 卷 期：2007年第17卷第3期

页      面：352-359页

核心收录：

学科分类：09[农学] 0902[农学-园艺学] 090202[农学-蔬菜学] 

基　　金：Project supported by the National Natural Science Foundation of China (No. 40571141) the Natural Science Foundation of Guangdong Province (No. 021007) the Key Teachers Foundation of the Ministry of Education of China (No. 2000-143-39) 

主　　题：Brassica parachinensis cadmium plant sap resistance speciation 

摘      要：Sap mixtures of the xylem, phloem, and vacuoles from low and high Cd accumulator varieties of Brassica parachinensis L. H. Bailey were analyzed under Cd stress to understand the biochemical mechanisms of Cd accumulation in plants. Low Cd accumulator ( Teqing-60 ) and high Cd accumulator ( Chixin-2 ) plants were grown in Cd-treated soil in pots in a greenhouse. Percentage of cell wall-bound Cd was estimated. pH level and the concentrations of amino acids, organic acids, anions, and cations in both stem and root saps were determined for the calculation of Cd speciations using the computer program GEOCHEM. The results showed that Teqing-60 had a significantly higher (P≤0.05) percentage of Cd bound to cell walls in roots and a significantly higher (P≤0.05) pH in the root sap. Teqing-60 also contained a higher concentration of total amino acids in both roots and stems compared with the high Cd accumulator variety Chixin-2 . However, between the two accumulators, for stems and for roots, there were no significant differences in non-amino organic acids. GEOCHEM calculations showed that Cd in the root sap of Teqing-60 mainly combined with amino acids, especially alanine. Compared with Chixin-2 , in the root sap of Teqing-60 , much lower levels of Cd as free ions or bound to simple ligands were found, indicating that less Teqing-60 is transferred to stems and leaves. Cadmium activity in the shoot sap of Teqing-60 was much lower than that in Chixin-2 ; therefore, Teqing-60 exhibited higher Cd resistance. However, direct determination of the Cd complexes from xylem and phloem sap is needed to verify these results.