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.

An Arabidopsis Mitochondrial Uncoupling Protein Confers Tolerance to Drought and Salt Stress in Transgenic Tobacco Plants

“…The effects of drought stress on plant respiration vary according to the severity of the stress and also among species [52]. The increase in respiration observed in WT plants could reflect a strategy by the plant to increase ATP levels to repair the damage caused by drought and salt stress, as demonstrated by Slot et al [53] in drought-stressed Geum urbanum leaves. Considering that AtUCP1 overexpression reduced the deleterious effects of abiotic stress, the need for higher respiration rates was reduced, leading to higher biomass accumulation, which might also be enhanced by the higher photosynthesis under stress.…”

Characterizing the drivers of seedling leaf gas exchange responses to warming and altered precipitation: indirect and direct effects

“…This result may reflect a longer-term response to prolonged drought stress that increased the demand for maintenance respiration, as has been seen in other studies (Gratani et al . 2007; Slot et al . 2008; Atkin and Macherel 2009).…”

“…2006), but drought may also increase respiration as result of increased respiratory demand for ATP (Atkin and Macherel 2009) or increased maintenance respiration (Gratani et al . 2007; Slot et al . 2008).…”

Contrasting thermal acclimation of leaf dark respiration and photosynthesis of Antarctic vascular plant species exposed to nocturnal warming

“…Plant photosynthesis and respiration (R) are interdependent processes but are both dependent on leaf temperature. However, both processes respond differently and non‐linearly to environmental temperature (Slot et al ), with respiration being more sensitive to temperature (Amthor ), which may have a significant impact on plant carbon gain (Turnbull et al ). Turnbull et al () reported that nocturnal temperatures have a significant effect on the photosynthetic capacity of leaves during the subsequent day, through its impact on leaf respiration and carbohydrate status.…”