ICOM1 Abstract

or a Talk session: Physiology BRUNNER, IVANO & BEAT FREY. Swiss Federal Institute for Forest, Snow and Landscape Research, 8903 Birmensdorf, Switzerland. - Effects of media lacking one nutritional element on ectomycorrhizal development and plant growth or 'how to recognize a functioning ectomycorrhiza' Birch seedlings (Betula pendula), inoculated with the ectomycorhizal fungus Paxillus involutus, were grown in Petri dishes on media deficient in K, Na, Ca, or Mg, and with Cl lacking in all treatments. The experiments have shown, that the formation of ectomycorrhizae occurred frequently in the K- and Na-lacking treatment, but only occasionally in the Mg- and Ca-lacking treatment. The lack of either one of these nutritional elements resulted in a discoloration of leaves other than cotyledons. With addition of the lacking nutritional elements as chloride solutions into small aluminum pots accessible only to extramatrical mycelia, however, a recovering of the leaf color was evident. Additionally, CsCl was applied as a tracer solution. In freeze- fractured ectomycorrhizal roots, the detection of elements using energy dispersive X-ray analysis (EDX) lead to the following conclusions: 1) Cs and Cl are useful tracers detectable in various compartments of ectomycorrhizae indicating an uptake by hyphae and transport across the interface; 2) K is not a valuable parameter, since it also can be detected in plant parts grown on media deficient in K (K probably originates from the seeds); 3) Na, Ca, and Mg often are not in a sufficient amount present which prevents a clear interpretation. In addition, the above mentioned media were supplemented with 525 mM N (as ammoniumnitrate), since earlier studies showed the induction of callose formation in epidermal and cortical cells of birch ectomycorrhizae due to elevated N-concentrations. The potential and limitations of the systems and techniques used to show the 'functioning' of such symbioses are discussed.