Acclimation of the respiration photosynthesis ratio to temperature: insights from a model

Based on short-term experiments, many plant growth models - including those used in global change research - assume that an increase in temperature st imulates plant respiration (R) more than photosynthesis (P), leading to an increase in the R/P ratio. Longer-term experiments, however, have demonstra ted that R/P is relatively insensitive to growth temperature. We show that both types of temperature response may be reconciled within a simple substr ate-based model of giant acclimation to temperature, in which respiration i s effectively limited by the supply of carbohydrates fixed through photosyn thesis. The short-term, positive temperature response of R/P reflects the t ransient dynamics of the nonstructural carbohydrate and protein pools; the insensitivity of R/P to temperature on longer time-scales reflects the stea dy-state behaviour of these pools. Thus the substrate approach may provide a basis for predicting plant respiration responses to temperature that is m ore robust than the current modelling paradigm based on the extrapolation o f results from short-term experiments. The present model predicts that the acclimated R/P depends mainly on the internal allocation of carbohydrates t o protein synthesis, a better understanding of which is therefore required to underpin the wider use of a constant R/P as an alternative modelling par adigm in global change research.