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Thermal Acclimation (thermal + acclimation)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Thermal acclimation of photosynthesis: a comparison of boreal and temperate tree species along a latitudinal transect

PLANT CELL & ENVIRONMENT, Issue 6 2010
DYLAN N. DILLAWAY
ABSTRACT Common gardens were established along a ,900 km latitudinal transect to examine factors limiting geographical distributions of boreal and temperate tree species in eastern North America. Boreal representatives were trembling aspen (Populus tremuloides Michx.) and paper birch (Betula papyrifera Marsh.), while temperate species were eastern cottonwood (Populus deltoides Bartr ex. Marsh var. deltoides) and sweetgum (Liquidambar styraciflua L.). The species were compared with respect to adjustments of leaf photosynthetic metabolism along the transect, with emphasis on temperature sensitivities of the maximum rate of ribulose bisphosphate (RuBP) carboxylation (EV) and regeneration (EJ). During leaf development, the average air temperature (Tgrowth) differed between the coolest and warmest gardens by 12 °C. Evidence of photosynthetic thermal acclimation (metabolic shifts compensating for differences in Tgrowth) was generally lacking in all species. Namely, neither EV nor EJ was positively related to Tgrowth. Correspondingly, the optimum temperature (Topt) of ambient photosynthesis (Asat) did not vary significantly with Tgrowth. Modest variation in Topt was explained by the combination of EV plus the slope and curvature of the parabolic temperature response of mesophyll conductance (gm). All in all, species differed little in photosynthetic responses to climate. Furthermore, the adaptive importance of photosynthetic thermal acclimation was overshadowed by gm's influence on Asat's temperature response. [source]

Inaccurate or disparate temperature cues?

FUNCTIONAL ECOLOGY, Issue 5 2010
Seasonal acclimation of terrestrial, aquatic locomotor capacity in newts
Summary 1.,Many organisms respond to seasonal temperature fluctuations by the reversible modification of whole-animal performance. Semiaquatic ectotherms, which possess this acclimatory capacity in swimming speed, lack the plastic response in terrestrial locomotor performance and vice versa. Theory predicts that the presence of reversible (seasonal) thermal acclimation or fixed phenotypes depends on the predictability of future thermal conditions (i.e. accuracy of temperature cues) in a given environment. Alternatively, comparative data suggest that thermal acclimation is induced by disparate temperature cues in water and on land. 2.,We tested both predictions by examining the seasonal acclimation response in thermal sensitivity of maximal swimming and running speed in adult alpine newts, Ichthyosaura (formerly Triturus) alpestris. 3.,Following the seasonal variation in environmental temperatures, we exposed newts to 5 °C from November to March and, after a gradual temperature increase, to either a constant (15 °C) or fluctuating (10,20 °C) thermal regime from May to June. At the end of each treatment, we measured newt swimming and running capacity at five temperatures (range 5,25 °C). In the field, hourly temperatures were recorded in various aquatic and terrestrial microhabitats to obtain information about the predictability of thermal conditions in both environments. 4.,Seasonal acclimation shaped the thermal sensitivity of swimming speed under both constant and fluctuating temperature treatments. Thermal sensitivity of running speed was markedly modified by a fluctuating thermal regime so that newts ran at the highest test temperature faster than cold-acclimated individuals. Natural thermal environment contained a similar proportion of predictable variation in water and on land. 5.,Complex seasonal acclimation of locomotor capacity in newts was influenced by the disparate thermal cues, i.e. mean acclimation temperature or diel temperature fluctuations, rather than by the different accuracy of these cues in water and on land. Future confrontations of theory with empirical data will require more attention not only on the assumptions of adaptive thermal acclimation but also on the ecologically relevant thermal conditions during acclimation experiments. [source]