Pedosphere 10(4): 347--354, 2000
ISSN 1002-0160/CN 32-1315/P
©2000 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Bio-mobilization of potassium from clay minerals: Ⅱ. By ectomycorrhizal fungi |
| YUAN Ling, WANG Zhi-Hui, FANG De-Hua, SHUN Hong and HUANG Jian-Guo |
| College of Resources and Environment, Southwest Agricultural University, Chongqing 400716 (China) |
| ABSTRACT |
| Ectomycorrhizal fungi, including Cenococcum geophilum SIV (Cg SIV), and Pisolithus tinctorius 2144 (Pt 2144), 441 (Pt 441) and XC1 (Pt XC1), were cultured in Pachlewski liquid medium with H2KPO4, KCl-saturated vermiculite and mica as K sources, respectively, to investigate the mechanism of K absorption and mobilization by the fungi. Fungal growth rate, K absorption and mobilization varied significantly among the fungal species. Faster growth and greater K accumulation in Pt XC1 than Pt 2144, Pt 441 and Cg siv were observed. Ectomycorrhizal fungi depressed HCl-soluble K in minerals after successive extractions by water and NH4OAc. Ratio of the total amount of K, including water-, NH4OAc- and HCl-soluble K, lost from substrates to the K accumulated in fungal colonies was less than 60%. These reveal that the ectomycorrhizal fungi could utilize K in interlayer and structural pools, which are usually unavailable for plants in short period. Large differences in the depletion of K in interlayer and structural pools by fungi were observed at fungal harvest. Taking into account the nutrient absorption by ectomycorrhizal fungi in symbionts and the direct contact between hyphae and soils, the fungi species colonized on the root surfaces seemed to be related to the effectiveness of mycorrhizas to utilize K in soils. Ectomycorrhizal fungi differed in the efflux of protons and oxalate. Pt XC1 was observed to have greatest ability to effuse protons and oxalate among the fungi adopted in the experiment. Furthermore, the higher the concentrations of protons and oxalate in the liquid culture solutions, the larger the depletion of K in interlayer and structural pools in minerals by fungi. Protons could replace interlayer K and chelation of oxalate with Fe and Al in crystal lattice could cause weathering of clay minerals. So, protons and oxalate produced by ectomycorrhizal fungi might play an important role in K mobilization in these two pools. |
| Key Words: ectomycorrhizal fungi, K, proton and oxalate |
| Citation: Yuan, L., Wang, Z. H., Fang, D. H., Shun, H. and Huang, J. G. 2000. Bio-mobilization of potassium from clay minerals: Ⅱ. By ectomycorrhizal fungi. Pedosphere. 10(4): 347-354. |
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