WATER-UPTAKE BY SAFFLOWER AND WHEAT ROOTS INFECTED WITH ARBUSCULAR MYCORRHIZAL FUNGI

The objective of this study was to determine if infection by arbuscula r mycorrhizal fungi alters water uptake by roots under well watered to severely droughted conditions. Safflower and wheat plants were grown with and without the mycorrhizal fungi, Glomus etunicatum or G. intrar adices in nutrient-amended soil under environmentally controlled condi tions to yield mycorrhizal and non-mycorrhizal plants with similar lea f areas, root length densities, d. wt, and adequate tissue phosphorus and nitrogen. Specific water uptake rates (cm(3) of water cm(-1) root length d(-1)) were estimated non-destructively at various depths in th e soil from changes in the soil water cm content measured using a gamm a attenuation method. When soil water was severely depleted, changes i n soil water potentials were also measured with soil psychrometers. Ro ots from both plant species extracted water at the fastest rate from t he upper soil layers when the soil water content was high, and later, extracted water primarily from deeper depths as water in the upper soi l layers was depleted. Mycorrhizal infection did not affect the rates at which roots extracted water from soil whether soil moisture conditi ons were at their wettest condition, at container capacity, or at the driest extreme when soil water potentials ranged from -1.5 to -2.0 MPa and the plants were completely wilted. Plant water relations were als o largely unaffected by infection. Mycorrhizal infection did not alter the ability of plants to extract water from soil even during extreme drought.