Showing papers by "Owen K. Atkin published in 2008"

Using temperature-dependent changes in leaf scaling relationships to quantitatively account for thermal acclimation of respiration in a coupled global climate-vegetation model

Abstract: The response of plant respiration (R) to temperature is an important component of the biosphere's response to climate change. At present, most global models assume that R increases exponentially wi ...

Dynamic changes in the mitochondrial electron transport chain underpinning cold acclimation of leaf respiration.

Abstract: We examined the effect of short- and long-term changes in temperature on gene expression, protein abundance, and the activity of the alternative oxidase and cytochrome oxidase pathways (AOP and COP, respectively) in Arabidopsis thaliana. The AOP was more sensitive to short-term changes in temperature than the COP, with partitioning to the AOP decreasing significantly below a threshold temperature of 20 °C. AOP activity was increased in leaves, which had been shifted to the cold for several days, but this response was transient, with AOP activity subsiding (and COP activity increasing) following the development of leaves in the cold. The transient increase in AOP activity in 10-d cold-shifted leaves was not associated with an increase in alternative oxidase (AOX) protein or AOX1a transcript abundance. By contrast, the amount of uncoupling protein was significantly increased in cold-developed leaves. In conjunction with this, transcript levels of the uncoupling protein-encoding gene UCP1 and the external NAD(P)H dehydrogenase-encoding gene NDB2 exhibited sustained increases following growth in the cold. The data suggest a role for each of these alternative non-phosphorylating bypasses of mitochondrial electron transport at different points in time following exposure to cold, with increased AOP activity being important only in the early stages of cold treatment.

Transient shade and drought have divergent impacts on the temperature sensitivity of dark respiration in leaves of Geum urbanum.

Abstract: The respiratory response of plants to temperature is a critical biotic feedback in the study of global climate change. Few studies, however, have investigated the effects of environmental stresses on the short-term temperature response of dark respiration (Rdark) at the leaf level. We investigated the effect of shade and transient drought on the temperature sensitivity (Q10; the proportional increase in respiration per 10°C increase in temperature) of Rdark of Geum urbanum L. in controlled experiments. Shade effects were most pronounced following sustained, near-darkness, when rates of leaf Rdark at a set measuring temperature (25°C) and the Q10 of Rdark were both reduced. By contrast, rates of leaf Rdark and the Q10 of Rdark both increased in response to the onset of severe water stress. Water stress was associated with a rapid (but reversible) decline in rates of light-saturated photosynthesis (Psat), stomatal closure (gs) and progressive wilting. Re-watering resulted in a rapid recovery of Psat, gs and a decline in the Q10 of Rdark (due to larger proportional reductions in the rate of Rdark measured at 25°C compared with those measured at 14°C). The concentration of soluble sugars in leaves did not decline during drought (5-7 day cycles) or shading, but during drought the starch concentration dropped, suggesting starch to sugar conversion helped to maintain homeostatic concentrations of soluble sugars. Thus, the drought and shade induced changes in Rdark were unlikely to be due to stress-induced changes in substrate supply. Collectively, the data highlight the dynamic responses of respiratory Q10 values to changes in water supply and sustained reductions in growth irradiance. If widespread, such changes in the Q10 of leaf respiration could have important implications for predicted rates of ecosystem carbon exchange in the future, particularly in areas that experience more frequent droughts.