Bidwell Sjaan D, Woodrow Ian E, Batianoff George N, Sommer-Knudsen Jens
School of Botany, The University of Melbourne, Vic. 3010, Australia.
School of Botany, The University of Melbourne, Parkville, Vic. 3052, Australia;Corresponding author; email:
Funct Plant Biol. 2002 Jul;29(7):899-905. doi: 10.1071/PP01192.
Throughout the world, over 400 species of plants are known to accumulate large quantities of metals in their shoots (`hyperaccumulators'), but of these, relatively few accumulate manganese (Mn). We have identified for the first time an Australian native hyperaccumulator of Mn, Austromyrtus bidwillii (Benth.) Burrett (Myrtaceae). Concentrations of Mn up to 19 200 µg g were measured in dried leaves of this rainforest tree, and young bark was found to contain up to 26 500 µg g Mn. Approximately 40% of the Mn in the leaves is readily extracted with water, suggesting that some of the Mn is associated with water-soluble compounds such as organic acids. Organic acids present in appreciable amounts in leaf extracts of A. bidwillii were identified and quantified by HPLC and gas chromatography-mass spectrometry. The following organic acids (in order of concentration) were present: succinic > malic ≥ malonic > oxalic >> citric acid. The concentration of total organic acids was on average 123 000 µg g dry tissue, which amounted to approximately three times the molar equivalent of Mn and two times the molar equivalent of total cations (Mn, Mg and Ca), demonstrating that organic anions were in excess. The Mn remaining after water extraction ((61 ± 3.9%) could be extracted with 0.2M HCl, suggesting that a significant portion of the Mn is associated with the cell wall (perhaps replacing Ca) or is present as other insoluble compounds.
在全球范围内，已知有400多种植物能在其地上部分积累大量金属（“超积累植物”），但其中相对较少的植物能积累锰（Mn）。我们首次鉴定出一种澳大利亚本土的锰超积累植物，即比氏澳香桃木（Austromyrtus bidwillii (Benth.) Burrett，桃金娘科）。在这种雨林树木的干燥叶片中测得的锰含量高达19200μg/g，并且发现幼嫩树皮中含锰量高达26500μg/g。叶片中约40%的锰可用水轻易提取出来，这表明部分锰与水溶性化合物如有机酸有关。通过高效液相色谱法（HPLC）和气相色谱 -质谱联用技术对比氏澳香桃木叶片提取物中大量存在的有机酸进行了鉴定和定量。存在的有机酸如下（按浓度顺序）：琥珀酸＞苹果酸≥丙二酸＞草酸＞＞柠檬酸。总有机酸浓度平均为123000μg/g干组织，这大约相当于锰摩尔当量的三倍以及总阳离子（锰、镁和钙）摩尔当量的两倍，表明有机阴离子过量。水提取后剩余的锰（(61 ± 3.9%)）可用0.2M盐酸提取，这表明相当一部分锰与细胞壁有关（可能替代了钙）或作为其他不溶性化合物存在。
