Journal
PLANT CELL AND ENVIRONMENT
Volume 36, Issue 7, Pages 1268-1284Publisher
WILEY
DOI: 10.1111/pce.12057
Keywords
acclimation; Arrhenius; heat stress; leaves; Q10; respiration
Categories
Funding
- Australian Research Council [ARC FT0991448, DP0986823]
- Australian Research Council [DP0986823] Funding Source: Australian Research Council
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We tested whether snow gum (Eucalyptus pauciflora) trees growing in thermally contrasting environments exhibit generalizable temperature (T) response functions of leaf respiration (R) and fluorescence (Fo). Measurements were made on pot-grown saplings and field-grown trees (growing between 1380 and 2110m a.s.l.). Using a continuous, high-resolution protocol, we quantified T response curves of R and Fo - these data were used to identify an algorithm for modelling R-T curves at subcritical T's and establish variations in heat tolerance. For the latter, we quantified Tmax [T where R is maximal] and Tcrit [T where Fo rises rapidly]. Tmax ranged from 51 to 57 degrees C, varying with season (e.g. winter>summer). Tcrit ranged from 41 to 49 degrees C in summer and from 58 to 63 degrees C in winter. Thus, surprisingly, leaf energy metabolism was more heat-tolerant in trees experiencing ice-encasement in winter than warmer conditions in summer. A polynomial model fitted to log-transformed R data provided the best description of the T-sensitivity of R (between 10 and 45 degrees C); using these model fits, we found that the negative slope of the Q10-T relationship was greater in winter than in summer. Collectively, our results (1) highlight high-T limits of energy metabolism in E.pauciflora and (2) provide a framework for improving representation of T-responses of leaf R in predictive models.
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