The use of laser scanning confocal microscopy to characterize mycorrhizas of Pinus strobus L. and to localize associated bacteria

 Laser scanning confocal microscopy (LSCM), light microscopy (LM) and epifluorescence microscopy (FM) were used to observe the extramatrical hyphae, mantle patterns and associated bacteria on mycorrhizal tips of Pinus strobus L. seedlings grown in pot cultures. Laccaria sp. and Tuber sp. formed ectomycorrhizas with Pinus strobus, while Phialophora finlandia Wang & Wilcox and E-strain (sensu Danielson 1982) formed ectendomycorrhizas. Distinct mantle patterns and cystidia were observed with greater resolution using LSCM, and intracellular hyphae were visualized in three dimensions. Trypan blue penetrated fresh whole mounts to 20 μm and was an excellent stain for visualizing fungal hyphae and bacteria with LSCM. Fluorescein isothiocyanate and acridine orange were used in conjunction with LSCM and FM to localize bacteria on ectomycorrhizal tips. With LSCM, bacteria were visible in the surface mucigel, and optical sectioning through the root tip showed that bacteria were also present within the mantle. LSCM is a non-intrusive and fast method for visualizing mycorrhizal structures and their associated bacteria on fresh, whole root tips. Accepted: 17 July 1996