Temperature Adaptation and Acclimation Potential of Leaf Dark Respiration in Two Species of Ranunculus from Warm and Cold Habitats

Rates of evolutionary thermal adaptation (i.e. hereditary adjustment to the thermal environment) of plant dark respiration will likely be too slow to keep up with predicted rapid climate changes. However, thermal acclimation to novel temperatures (i.e. shorter-term phenotypic adjustment to changes in the thermal environment) may be sufficient for plants to adjust to rapidly changing temperatures. We measured nighttime leaf dark respiration in the arctic/alpine species Ranunculus glacialis, and in the temperate lowland Ranunculus repens, on plants grown under either cold (100C/80C day/night) or warm (220C/180C) conditions. Adaptation to their respective native thermal environments was apparent in this pair of species as indicated by similar respiration rates measured at 80C in R. glacialis grown at cold temperatures and those measured at 180C in R. repens grown at warm temperatures. Phenotypic thermal acclimation to warmer temperatures was apparent in R. glacialis as indicated by similar rates measured at 80C in cold-grown and at 180C in warm-grown plants. Whether this holds true for root systems awaits testing. Our results reemphasize the need to include acclimatory adjustments of plant metabolism in computer models designed to predict the response of vegetation to global change.