Acclimation of leaf respiration temperature responses across thermally contrasting biomes
New Phytol. 2020 Sep 15, Online ahead of print
Zhu L, Bloomfield KJ, Asao S, Tjoelker MG, Egerton JJG, Hayes L, Weerasinghe LK, Creek D, Griffin KL, Hurry V, Liddell M, Meir P, Turnbull MH, Atkin OK

Abstract
Short-term temperature response curves of leaf dark respiration (R-T) provide insights into a critical process that influences plant net carbon exchange. This includes how respiratory traits acclimate to sustained changes in the environment. Our study analyses 860 high-resolution R-T (10-70°C range) curves for: (a) 62 evergreen species measured in two contrasting seasons across several field sites/biomes; and (b) 21 species (sub-set of those sampled in the field) grown in glasshouses at 20/15, 25/20 and 30/25 °C (day/night). In the field, across all sites/seasons, variations in R25 (measured at 25 °C) and the leaf-T where R reached its maximum (Tmax ) were explained by growth-T (mean air-T of 30-days prior to measurement), solar irradiance and vapor pressure deficit, with growth-T having the strongest influence. R25 decreased and Tmax increased with rising growth-T across all sites and seasons with the single exception of winter at the cool-temperate rainforest site where irradiance was low. The glasshouse study confirmed that R25 and Tmax thermally acclimated. Collectively, the results suggest: (1) thermal acclimation of leaf R is common in most biomes; and, (2) the high-T threshold of respiration dynamically adjusts upward when plants are challenged with warmer and hotter climates.

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