Temperature coefficient (Q₁₀) for growth of plant pathogens and other organisms is about 3 below the optimum temperature and 9 above the optimum temperature.[sic]  Q₁₀ is useful or essential in studies of heat inactivation and heat therapy, and averages about 100 for these purposes, but differs greatly for different situations, and decreases with increasing temperature.  Q₁₀ for heat injury to higher plants is usually lower than for inactivation of microorganisms including plant pathogens.  Q₁₀'s for heat inactivation of fungi, bacteria, and viruses are not clearly different.  The highest Q₁₀ observed in this study was about 150 for inactivation of tobacco mosaic virus, and the lowest was 7 for tobacco necrosis virus.

Additional key words: control of phytoalexin synthesis.