ERGOSTEROL ANALYSIS AS A MEANS OF QUANTIFYING MYCORRHIZAL BIOMASS

This chapter describes the ergosterol analysis as a means of quantifying mycorrhizal biomass. A fundamental problem concerns the concept of fungal biomass: while the chitin content may be assumed to be roughly proportional to the total amount of cell wall, the amount of cell wall is certainly not proportional to the amount of cytoplasm, which is normally concentrated at the tips, leaving the bulk of the hyphae highly vacuolated. Another fungus-specific compound, ergosterol, is a principal component of membranes, and should therefore provide a better correlation with the metabolically active biomass of a fungus. The chapter briefly discusses development and current procedure technique. The chapter also evaluates the methods—namely, sensitivity and replicability, variation in ergosterol levels within the same species, and applications in mycorrhiza research. The basic shortcomings of the method are those of variation in the ergosterol content depending on growing conditions, and interspecies variation. © 1992 Academic Press Limited