CYTOLOCALIZATION OF GLYCOGEN, STARCH, AND OTHER INSOLUBLE POLYSACCHARIDES DURING ONTOGENY OF PAXILLUS-INVOLUTUS BETULA-PENDULA ECTOMYCORRHIZAS

The Paxillus involutus (Fries) Karsten-Betula pendula Roth association was studied during the early stages of formation. Cytological studies revealed fungal colonization behind the root cap and gradually around the entire root apex. Ultrastructural investigations were carried out and insoluble polysaccharide distribution was followed. The density o f starch grains increased in plant cells especially after 4 d of conta ct between the two partners, but later on decreased strongly in the ro ot cap. Large amounts of glycogen were revealed in the hyphae in certa in mycorrhizal regions after 6 d of contact: in the Hartig net, in the inner sheath but only near the net, and all along the outer sheath su rrounding the mycorrhiza. Thickenings of the epidermal cell walls were detected as early as 2 d after contact and then varied according to t he distance from the root tip. Such polysaccharide distributions are a ssumed to show a transfer of carbohydrates from the root to the fungus and are discussed in terms of carbon requirements for both partners.