The cost of living : temperature compensation of the metabolic rate in plants

Abstract

The basal metabolic rate of organisms, the rate at which organisms take up, transform and expend energy and material is highly important for whole ecosystem functioning. Differences in the basal metabolic rate might be described by its biomass and temperature dependence. The Metabolic theory of ecology (MTE) claims that the basal metabolic rate (B) of all organisms should be described by: B=b0*M^3/4*e^-E/kT , where, b0 is the species-specific normalization constant, the term M^3/4 describes the scaling on biomass (M) and the Arrhenius-term e^-E/kT is a formalization of the thermodynamic effect of temperature effect on the metabolic reaction rate of key-enzymes. This thesis provides an important contribution to the already extensive debate triggered by the MTE. We show that for species from different thermal environments the metabolic rate can not simply be described by the Arrhenius-term. By acclimation and adaptation organisms appear to adjust to different thermal environments. Furthermore, the biomass scaling for plants might result from size-dependent variations in biomass allocation patterns, as different tissues differ in their metabolic activity. In addition the leaf construction is important for differences in the metabolic rate of plants. Differences in leaf construction are related to species-specific traits, but also to thermal life history, indicating that temperature compensation of the metabolic rate does not only occur adjusting enzymatic reaction but also through changes morphological features. It is concluded that the environmental impact on the metabolic rate of plants is much more complex than described by the MTE.