Role of a VA Mycorrhizal Fungus on Growth and Water Relations in Wheat in Presence of Organic and Inorganic Phosphates

Wheat (Triticum aestivum L.) was grown under axenic conditions in two soils in pots which were separated by 30 pm nylon nets and 0.45 μm membrane into five compartments, a central one for root growth and two adjacent of the central compartment for hyphal growth and two outer ones for control. The treatments comprised sterilized soil, supply of organic or inorganic phosphate (P), either uninoculated or inoculated with Glomus mosseae. Compared to non-inoculated (sterile) control, inoculation with VAM significantly increased shoot and root dry weight and total root length, although shoot: root ratio was unaffected. The effect depends on soil type and form of P present in the soil. In mycorrhizal plants, the total transpiration was Significantly higher but transpiration coefficient was not affected due to inoculation. For several reasons a substantial hyphal water transport seems unlikely. The results stress the necessity of detailed studies on root morphology for interpretation of effects of mycorrhizal fungi on mineral nutrient uptake and water relations in plants.