WATER AND NUTRIENT TRANSLOCATION BY HYPHAE OF GLOMUS-MOSSEAE

To test the ability of vesicular-arbuscular mycorrhizal (VAM) hyphae to take up water, phosphorus, and potassium, mycorrhizal and nonmycorrhizal couchgrass (Agropyron repens) or white clover (Trifolium repens) plants were grown in pots with separated compartments for roots and hyphae growth. Soil solution transfer between compartments was blocked by a 2-mm air gap. Total shoot contents of phosphate and nitrogen, but not of potassium, were higher in mycorrhizal plants with access to the hyphal compartment. Hyphal uptake from the outer compartment accounted for 49 % of the total phosphate and 35 % of the total nitrogen taken up by mycorrhizal plants. This was associated with depletion of extractable phosphate, NH4+-nitrogen, and also NO3--nitrogen in the soil of the hyphal compartments. In contrast, no difference in water loss from the hyphal compartments was measured by tensiometers under well-watered and water-stress conditions whether hyphae were present or not. Severance of the external hyphae did not affect water loss from the outer compartments. The results show the ability of VAM hyphae to transport considerable quantities of phosphate and nitrogen to the plant from soil zones several centimetres from the root. However, there was no evidence for a significant direct water transport by VAM hyphae to plants.