Global warming over the next century is likely to be associated with a change in the extent to which atmospheric
and soil temperatures fluctuate, on both a daily and a seasonal basis. The average annual temperature of the Earth's
surface is expected to increase, as is the frequency of hot days. In this review, we explore what effects short-term
and long-term changes in temperature are likely to have on root respiratory metabolism, and what impacts such
changes will have on daily, seasonal and annual CO2 release by roots under field conditions. We demonstrate that
Q10 values, and the degree of acclimation, differ between and within plant species. Changes in the temperature
sensitivity of respiration with measuring temperature are highlighted. Temperature-dependent changes in
adenylate control and substrate supply are likely to control the Q10 and degree of acclimation of root respiration.
Limitations in respiration capacity are unlikely to control respiratory flux at most temperatures. The potential role
of nonphosphorylating pathways such as the alternative oxidase in controlling Q10 values is highlighted. The
possibility that potentially rapid changes in adenylate control might underlie the acclimation response (rather than
slow changes in enzyme capacity) has implications for the total amount of CO2 respired by roots daily and
annually. Our modelling suggests that rapid acclimation will result in near-perfect homeostasis of respiration rates
and minimize annual CO2 release. However, annual CO2 release increases substantially if the speed of full
acclimation is lower. Our modelling exercise also shows that high Q10 values have the potential to increase daily
and annual CO2 release substantially, particularly if the frequency of hot days increases after global warming.