Response of Plant Respiration to Changes in Temperature: Mechanisms and Consequences of Variations in Q10 Values and Acclimation

Abstract

The effects of short- and long-term changes in temperature on plant respiration (R) are reviewed. We discuss the methods available for quantifying the short- and long-term temperature-dependence of R. The extent to which the Q10 (the proportional change in R with a 10 °C increase in temperature) and the degree of thermal acclimation (change in the temperature-response curve of R following a long-term change in growth temperature) vary within and amongst plant species are assessed. We show that Q10 values are highly variable (e.g., being affected by measuring and growth temperature, irradiance and drought), but most plant species exhibit similar Q10 values (in darkness) when grown and measured under identical conditions (i.e. little evidence of inherent differences in the Q10 of plant R). The possible mechanisms responsible for variability in the Q10 are discussed; high Q10 values occur in tissues where respiratory flux is substrate saturated (i.e. capacity limited). This is illustrated using plots of reduced ubiquinone versus O2 uptake in isolated mitochondria. The degree of acclimation is also highly variable amongst plant species. This variability is due, in part, to some studies exposing pre-existing roots/leaves to a new growth temperature, whereas others compare roots/leaves that develop at different temperature. In most cases, maximal acclimation requires that new leaves and/or roots be developed following a change in growth temperature. In addition to its link with development, acclimation is also often associated with changes in the Q10, particularly in pre-existing leaves/roots transferred from one environment to another. The importance of acclimation in determining annual rates of R as a component of net primary productivity and net ecosystem CO2 exchange is discussed. The importance of acclimation for future atmospheric CO2 concentrations is highlighted, including a positive feedback effect of climate warming on the carbon cycle. This review shows that the assumptions of coupled global circulation models (that Q10 values are constant and that R does not acclimate to long-term changes in temperature) are incorrect, and this may lead to overestimation of the effects of climate warming on respiratory CO2 flux.