PVLG is used to permanently mount whole or broken spores on glass slides. For best results, mounted specimens should not be studied for 2-3 days after they were mounted to give time for spore contents to clear. Whole spores will change color, generally darkening to varying degrees, and shrink or collapse with plasmolysis of spore contents. Discrete layers of the spore wall or flexible inner walls of broken spores will swell to varying degrees and appear fused after long storage in some instances.

When Melzer's reagent is used according to the recipe above, staining reactions will be most intense. However, mounts are temporary even when a coverslip is sealed, and often dries out within 1-2 years of storage. More permanent mounts are made by mixing Melzer's reagent with PVLG in a volume ratio of 1:1 (and storing the mixture in a dark bottle). The staining reaction is diminished slightly, but not enough to cause any confusion as to the intensity of the reaction. In structures staining weakly, the color reaction fades within a year or two of storage.

Sodium azide is a respiratory inhibitor and therefore should be handled with care (wearing gloves) in the preparation of stock solutions (2.5 g in 50 ml of distilled water). A one ml aliquot of the stock is added to 90 ml of distilled water for a 0.05% working solution.

For vial vouchers, spores are collected and added to 2 ml vials in a minimum of water. The vial is then filled with the sodium azide working solution and labelled. Solutions and vials are stored at 4^oC as an added precaution to optimize safety of the workplace.

Spores die in the sodium azide and therefore will begin to degrade naturally over time. They will begin to float, contents often darken or lose their integrity (appearing either cloudy or vacant). However, subcellular structures largely retain their integrity. Other preservative solutions such as FAA (Formalin + Acetic Acid + Alcohol) and lactophenol (lactic acid + phenol) have been used extensively in the past, but evidence from type specimens indicates they can cause major changes or degradation of subcellular structure of spores.

Serendipitously, on one occasion we stored washed spores of Gigaspora gigantea in distilled water at 4^oC and were surprised to discover that the spores did not change color after 30 days. In contrast, spores stored in sodium azide or any other preservative turn red-brown to brown within 10 days. We have since tried this with other fungi, and obtain similar results. When the spores are killed by the preservative, some degradation of structure occurs. The only drawback with storing in water is that any parasitized spores (often not detectable at the time of extraction) will be a source of spread of colonizing fungal saprophytes or actinomycetes to adjacent spores. The approach we have taken to minimize this problem is similar to that used to prepare spore samples slated for molecular studies (viewed here). Fungal species with small (< 150 µm) light-colored spores tolerate these conditions best (large darkly pigmented spores tend to degrade no matter what), and we have stored some of them for over a year this way. Avoid Ringer's and other solutions that provide an isotonic environment; buffering appears to serve no useful purpose and in some cases, causes plasmolysis.