n. Traits of an organism that mitigate heating of cells to potentially lethal temperatures.
According to Levitt (1980), there are two kinds of resistance to injury, whether caused by fire or other forces: tolerance and avoidance. Fire tolerance is a kind of resistance that describes a trait or property of a species that mitigates dangerous, often lethal conditions. In regard to fire, tolerance refers to a state in which living cells are severely heated but survive anyway; this state is rare.
Fire tolerance is unusual in living organisms since it requires that tissues survive temperatures ordinarily considered high enough to denature proteins and disrupt metabolic functions (above 60oC, according to Hare 1961). Seeds, which have low water content and are metabolically inactive, may survive higher temperatures than this. For example, seeds of several California chaparral species have survived exposure to 180oC for up to five minutes (Sampson 1944). Survival of extreme temperatures is more likely due to heat resistance than to heat tolerance (Whalen 1995).