Chapter 8
Environmental conditions for
growth, and tolerance of extremes
This chapter is divided into the following major sections:- some introductory comments
- temperature and fungal growth
- pH and fungal growth
- oxygen and fungal growth
- water availability and fungal growth
- effects of light on fungal growth
In common with all microorganisms, fungi are pro-
foundly affected by physical and physicochemical
factors, such as temperature, aeration, pH, water
potential, and light. These factors not only affect
the growth rate of fungi but also can act as triggers
in developmental pathways. In this chapter we con-
sider the effects of environmental factors on fungal
growth, including the extremes of adaptation to envir-
onmental conditions.Some introductory comments
A few introductory points must be made to put this
chapter into perspective.
1 We will be concerned primarily with the effects of
environmental factors on fungal growth, but we must
recognize that almost all organisms can grow over a
wider range of conditions than will support their
full life cycle. For this reason, pure culture studies
in laboratory conditions can be misleading – they do
not necessarily predict the ability of a fungus to main-
tain its population in nature.
2 Fungi often can tolerate one suboptimal factor if
all others are near optimal, but a combinationof
suboptimal factors can prevent fungal growth. For
example, several fungi can grow at low pH (less
than 4.0), and several can grow in anaerobic condi-
tions, but few if any fungi can grow when low pH
is combined with anaerobiosis.
3 Competitive interactions can restrict the growth of
a fungus to a much narrower range than we find in
laboratory conditions. A classic early example of
this is shown in Fig. 8.1, where wheat plants wereFig. 8.1Effect of temperature on infection of wheat
seedlings by the take-all fungus of cereals, Gaeuman-
nomyces graminis, in sterilized soil (top line) and unsterile
soil (bottom line). (From Henry 1932.)