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In the present study we investigated variations in leaf respiration in darkness (RD) and light (RL), and associated traits in response to season, and along a gradient of soil moisture, in Mediterranean woodland dominated by holm oak (Quercus ilex L.) in central and north-eastern Spain respectively. On seven occasions during the year in the central Spain site, and along the soil moisture gradient in north-eastern Spain, we measured rates of leaf RD, RL (using the Kok method), light-saturated photosynthesis (A) and related light response characteristics, leaf mass per unit area (MA) and leaf nitrogen (N) content. At the central Spain site, significant seasonal changes in soil water content and ambient temperature (T) were associated with changes in MA, foliar N, A and stomatal conductance. RD measured at the prevailing daily T and in instantaneous R-T responses, displayed signs of partial acclimation and was not significantly affected by time of year. RL was always less than, and strongly related to, RD, and RL/RD did not vary significantly or systematically with seasonal changes in T or soil water content. Averaged over the year, RL/RD was 0.66±0.05 s.e. (n = 14) at the central Spain site. At the north-eastern Spain site, the soil moisture gradient was characterised by increasing MA and RD, and reduced foliar N, A, and stomatal conductance as soil water availability decreased. Light inhibition of R occurred across all sites (mean RL/RD= 0.69±0.01 s.e. (n = 18)), resulting in ratios of RL/A being lower than for RD/A. Importantly, the degree of light inhibition was largely insensitive to changes in soil water content. Our findings provide evidence for a relatively constrained degree of light inhibition of R (RL/RD ~ 0.7, or inhibition of ~30%) across gradients of water availability, although the combined impacts of seasonal changes in both T and soil water content increase the range of values expressed. The findings thus have implications in terms of the assumptions made by predictive models that seek to account for light inhibition of R, and for our understanding of how environmental gradients impact on leaf trait relationships in Mediterranean plant communities. [ABSTRACT FROM AUTHOR]

The leaf respiration (RD) of grapevine (Vitis vinifera 'Chasselas') was measured under field conditions during the growing season in leaves of different physiological ages in relation to the temperature and plant water status. RD increased with the temperature and was particularly high in young growing leaves on primary and lateral shoots. The RD response to the temperature evolved over the season according to the type and age of the leaves and their phenology. Leaf aging (senescence) induced a decrease in RD at the end of the season. At constant temperatures (20 °C), the highest RD rates were measured during the rapid plant growth phase (the Q10 values were also the highest), and they progressively decreased to reach their lowest rates at the end of the growing season. The lowest RD values were measured on leaves that were inserted opposite the clusters of primary shoots at any period during the season. Water stress led to a reduction in RD, especially when the leaf temperature was above 20 °C. The nocturnal RD evolution showed that the RD rates were greatest at nightfall when the nocturnal temperatures were still high and leaf carbohydrate availability was at its highest; the rates gradually decreased to reach the lowest RD values just before dawn. [ABSTRACT FROM AUTHOR]

Accurate evaluation of dark respiration of plants is important for estimation of the plant carbon budget. The response of leaf dark respiration of winter wheat to changes in CO concentration and temperature was studied, using an open top chamber during 2011-2012, to understand how leaf dark respiration of winter wheat will respond to climate change. The results indicated that leaf dark respiration decreased linearly with increased CO concentration. Dark respiration decreased by about 11% under 560 μmol mol CO compared with that under 390 μmol mol CO. Leaf dark respiration showed an exponential relationship with temperature, and the temperature constant ( Q) was close to 2. Moreover, the responses of leaf dark respiration to CO concentration and temperature were independent. A leaf dark respiration model based on CO concentration and temperature responses was developed. This model provides a method for estimation of the leaf dark respiration rate of winter wheat under future climate change and guidance for establishment of crop carbon countermeasures. [ABSTRACT FROM AUTHOR]