Plants can survive the whole range of atmospheric temperatures from -89°C (recorded at Vostok in Antarctica www.ncdc.noaa.gov/oa/climate/globalextremes.html#sites) to 56.7°C (recorded in Death Valley, California; El Fadli et al., 2012) that occur on the surface of the Earth, as well as the associated higher temperatures (up to about 70°C) that occur in the surface of desert soils and in the surface tissues of slowly transpiring massive desert plants such as cacti (Nobel, 1988). The even higher surface temperatures of up to 300° C that occur in bushfires can be survived by fire-tolerant plants. Seeds are particularly hardy, though other tissues of some species can also survive an extremely wide temperature range. Most plants can only grow, however, over a much more limited range of temperatures from somewhat above freezing to around 40° C, while growth approaches the maximum over an even more restricted temperature range that depends on species, growth stage and previous environment. Useful information on plants and temperature may be found in Larcher (1995) and Long and Woodward (1988).

In this chapter the physical principles underlying the control of plant temperatures are described and the physiological effects of high and low temperatures outlined. The final section considers the more ecological aspects of plant adaptation and acclimation to the thermal environment.

Physical basis of the control of tissue temperature

As outlined in Chapter 5, the temperature of plant tissue at any instant is determined by its energy balance.