Do the biochemical kinetics of photosynthesis control higher-level plant processes? Testing a key assumption of metabolic scaling theory

Abstract:

Understanding how climate influences plant function is a longstanding goal of earth system science and is critical for forecasting the effects of climate change on the biosphere. Metabolic scaling theory (MST) hypothesizes that the temperature-dependence of higher-level plant processes (such as growth and productivity) are ultimately governed by the reaction kinetics of photosynthesis. Specifically, MST hypothesizes that rates of higher-level plant processes increase with temperature according to an Arrhenius relationship, with an activation energy corresponding to that of net photosynthesis. Here, we report results from the first direct experimental test of this hypothesis. We conducted growth chamber experiments with three plant species grown at six constant temperatures (5–30ºC). We measured net photosynthesis temperature response, biomass growth rate, plant tissue temperature, and several additional climate variables. These data were then used to estimate the activation energies of leaf-level photosynthesis and biomass growth rate. Some results were consistent with MST predictions, while others suggested areas where MST can be refined. These results provide further insight into the kinetic basis of plant metabolism and suggest how MST can be extended to better predict plant function across climate gradients and in response to climate change.