Plants often adjust their leaf mitochondrial (“dark”) respiration (Rd) measured at a standardized temperature such as 20°C (R20) downward after experiencing warmer temperatures and upward after experiencing cooler temperatures. These responses may help leaves maintain advantageous photosynthetic capacity and/or be a response to recent photosynthate accumulation, and can occur within days after a change in thermal regime. It is not clear, however, how the sensitivity and magnitude of this response change over time, or which time period prior to a given measurement best predicts R20. Nor is it known whether nighttime, daytime, or 24-hour temperatures should be most influential. To address these issues, we used data from 1620 Rd temperature response curves of 10 temperate and boreal tree species in a long–term field experiment in Minnesota, USA to assess how the observed nearly complete acclimation of R20 was related to past temperatures during periods of differing lengths. We hypothesized that R20 would be best related to prior midday temperatures associated with both photosynthetic biochemistry and peak carbon uptake rates that drive carbohydrate accumulation. Inconsistent with this hypothesis, prior night temperatures were the best predictors of R20 for all species. We had also hypothesized that recent (prior 3–10 days) temperatures should best predict R20 because they likely have stronger residual impacts on leaf-level physiology than periods extending further back in time, whereas a prior 1- to 2-day period might be a span shorter than one to which photosynthetic capacity and Rd adjust. There was little to no support for this idea, as for angiosperms, long time windows (prior 30–60 nights) were the best predictors, while for gymnosperms both near-term (prior 3–8 nights for pines, prior 10–14 nights for spruce/fir) and longer-term periods (prior 45 nights) were the best predictors. The importance of nighttime temperatures, the relatively long “time-averaging” that best explained acclimation, and dual peaks of temporal acclimation responsiveness in some species were all results that were unanticipated.
Bibliographical noteFunding Information:
We would like to thank Owen K. Atkin for stimulating discussion and helpful comments, and Nick Smith and two anonymous reviewers for excellent suggestions that improved revised versions of the manuscript. This research was supported by the U.S Department of Energy, Office of Science, and Office of Biological and Environmental Research award number DE-FG02-07ER64456; Minnesota Agricultural Experiment Station MN-42-030 and MN-42-060; the College of Food, Agricultural, and Natural Resources Sciences and Wilderness Research Foundation, University of Minnesota, and by the National Science Foundation, Biological Integration Institutes grant NSF-DBI-2021898.
© 2021 John Wiley & Sons Ltd.
- carbon cycle
- night temperature
- respiration (R)