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KMID : 0903620040450040183
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Journal of the Korean Society for Horticultural Science
2004 Volume.45 No. 4 p.183 ~ p.188
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Distribution of Metal Cations in Apoplastic Washing Fluid in Arbuscular Mycorrhizal Lettuce Plants
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Lee Yun-Jeong
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Abstract
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The distribution of metal cations in arbuscular mycorrhizal plants including apoplastic washing fluid in root was investigated. A centrifugation method for extracting apoplastic sap was modified to measure the metal concentrations in apoplastic washing fluid. In addition, a nutrient film technique (NFT) system was modified for production of large amounts of extraradical fungal hyphae to facilitate measuring metal concentration in the fungal mycelium itself. A high level of root colonization was maintained in the NFT system. The fungal biomass from NFT system was collected as much as 1 g fresh weight. Metal concentrations of external fungal hyphae were high in all metal elements (Cu, Zn, Cd, and Ni) tested without large difference between metal elements compared to those of root concentration. Mycorrhizal colonization resulted in higher shoot Cu and Zn concentrations and lower shoot Ni concentration than those in non-mycorrhizal plants. In water-soluble apoplastic washing fluid of the plant, Cu concentration was much lower than that of non-mycorrhizal plants. However, there was no difference in the Zn, Cd, and Ni concentrations in apoplastic washing fluid of mycorrhizal and non-mycorrhizal roots. The ratio of hyphae/root concentration was higher for Cu compared to that for Zn. The ratio of root/shoot concentration of Ni was higher in mycorrhizal plants compared to that in non-mycorrhizal plants. Therefore, we suggest that external fungal hyphae acquired all of the four metals (Cu, Zn, Cd, and Ni) non-selectively but the transfer of each metal from fungal hyphae to plants was different. In mycorrhizal roots, Cu may be remained mostly in the fungal part, e.g., arbuscule, and Zn may be translocated more preferentially from roots to shoots in mycorrhizal plants. Translocation of Ni from roots to shoots was restricted in AM plants. It may be due to immobilization of Ni in fungal hyphae indicating a protective effect of the fungus in AM plants against the toxic effect of Ni.
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KEYWORD
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Glomus mosseae, mycorrhizal colonization, mycorrhizal hyphae, nutrient film technique, nutrient translocation
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