Effects of volatile organic compounds on the growth and development of fungi

Abstract

I clearly realize that I have to begin this lecture with some comments up on th e formulation of its title. One might very justly ask why the property of being volatile should be chosen as an excuse for lumping together a larg e number of organic compounds, differing consid erably from each other in their chemical composition and physiological activity. In trying to answer this question one might first point to the obvious fact that volatile compounds, i.e. those compounds with a relatively high vapour pressure at physiological temperatures, are capable of approaching an organism not onl y through the liquid phase but also through the gas phase. This is important, in particular to organisms like th e fungi which have virtually every single vegetative cell exposed to the surrounding medium and where consequ entl y the surface to volume ratio is very high. Furthermore, many lipophilic compounds produced directly into the air and almost insoluble in water may, even at some distance from a donor source, accumulate faster in the plasma membrane of an acceptor cell, if the tr ansfer takes place via th e gas phase instead of via th e liquid ph ase. As has been pointed out recently by Dr Hutchinson (1971) these two different ways of transfer may also involve differenc es in th e risks of destruction or adsorption of th e diffusing substan ce, th e way through the air being less exposed to mechanisms of inactivation than the way through th e water. Since most fungi develop parts of their mycelia and th eir entire reproductive organs in th e air above a liquid phase or a substrate imbibed with water these facts are certainly highly relevant to this group of organisms. Having stated this as a justification not only for th e title but for presenting thi s paper, I want to ad d, that from other points of view, e.g . the metab olic roles of volatile compounds after they have entered the cell, it is meaningless to try to maintain a line of demarcation against the nonvolatile substances. The vola tile organic compounds I will deal with in this lecture ma y differ from one another by a factor of 10 as regards' vapour pressure,