Respiration is a core biological process that has important implications for the biochemistry, physiology, and ecology of plants. The study of plant respiration is thus conducted from several ...different perspectives by a range of scientific disciplines with dissimilar objectives, such as metabolic engineering, crop breeding, and climate-change modelling. One aspect in common among the different objectives is a need to understand and quantify the variation in respiration across scales of biological organization. The central tenet of this review is that different perspectives on respiration can complement each other when connected. To better accommodate interdisciplinary thinking, we identify distinct mechanisms which encompass the variation in respiratory rates and functions across biological scales. The relevance of these mechanisms towards variation in plant respiration are explained in the context of five core principles: (1) respiration performs three distinct functions; (2) metabolic pathway flexibility underlies respiratory performance; (3) supply and demand interact over time to set respiration rates; (4) acclimation involves adjustments in enzyme capacities; and (5) respiration is a complex trait that helps to define, and is impacted by, plant lifestyle strategies. We argue that each perspective on respiration rests on these principles to varying degrees and that broader appreciation of how respiratory variation occurs can unite research across scales.
BACKGROUND: Around the world, the frequency and intensity of droughts is increasing as a result of global climate change, with important consequences for the growth and survival of agricultural and ...native plant species. Understanding how plants respond to water stress is thus crucial for predicting the impacts of climate change on the crop productivity and ecosystem functioning. In contrast to the large number of studies assessing drought impacts on photosynthesis, relatively little attention has been devoted to understanding how mitochondrial respiratory metabolism is altered under water stress conditions. SCOPE: This review provides an overview of the impacts of water stress on mitochondrial respiration (R), combining studies at the whole-plant, individual organ, cellular and organelle levels. To establish whether there are clear patterns in the response of in vivo R to water stress, a wide range of root, leaf and whole-plant studies are reviewed. It is shown that water stress almost always inhibits R in actively growing roots and whole plants. However, in fully expanded, mature leaves the response is more variable, with water stress reducing R in near two-thirds of reported studies, with most of the remainder showing no change. Only a few studies reported increases in leaf R under severe water stress conditions. The mechanisms responsible for these variable responses are discussed. Importantly, the fact is highlighted that irrespective of whether drought increases or decreases respiration, overall the changes in R are minor compared with the large decreases in photosynthetic carbon gain in response to drought. Based on recent work highlighting the link between chloroplast and mitochondrial functions in leaves, we propose a model by which mitochondrial R enables survival and rapid recovery of productivity under water stress conditions. Finally, the effects of water stress on mitochondrial function, protein abundance and overall metabolism are reviewed.
Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global ...scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration—specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen (N
m
) and phosphorus (P
m
), we characterize how traits vary within and among over 50,000 ∼50 × 50-km cells across the entire vegetated land surface. We do this in several ways—without defining the PFT of each grid cell and using 4 or 14 PFTs; each model’s predictions are evaluated against out-of-sample data. This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than that in previous analyses. Our maps reveal that the most diverse grid cells possess trait variability close to the range of global PFT means.
Heatwaves are likely to increase in frequency and intensity with climate change, which may impair tree function and forest C uptake. However, we have little information regarding the impact of ...extreme heatwaves on the physiological performance of large trees in the field. Here, we grew Eucalyptus parramattensis trees for 1 year with experimental warming (+3°C) in a field setting, until they were greater than 6 m tall. We withheld irrigation for 1 month to dry the surface soils and then implemented an extreme heatwave treatment of 4 consecutive days with air temperatures exceeding 43°C, while monitoring whole‐canopy exchange of CO2 and H2O, leaf temperatures, leaf thermal tolerance, and leaf and branch hydraulic status. The heatwave reduced midday canopy photosynthesis to near zero but transpiration persisted, maintaining canopy cooling. A standard photosynthetic model was unable to capture the observed decoupling between photosynthesis and transpiration at high temperatures, suggesting that climate models may underestimate a moderating feedback of vegetation on heatwave intensity. The heatwave also triggered a rapid increase in leaf thermal tolerance, such that leaf temperatures observed during the heatwave were maintained within the thermal limits of leaf function. All responses were equivalent for trees with a prior history of ambient and warmed (+3°C) temperatures, indicating that climate warming conferred no added tolerance of heatwaves expected in the future. This coordinated physiological response utilizing latent cooling and adjustment of thermal thresholds has implications for tree tolerance of future climate extremes as well as model predictions of future heatwave intensity at landscape and global scales.
Heatwaves are likely to increase in frequency and intensity, but we know relatively little about how trees will respond. Here, we documented that large trees growing in the field responded to an extreme heatwave with a coordinated physiological response involving continued leaf cooling from transpiration and a rapid increase in leaf thermal tolerance. The Eucalyptus trees that we studied were remarkably capable of tolerating an extreme heatwave via mechanisms that have implications for future heatwave intensity and forest resilience in a warmer world.
Leaf day respiration Tcherkez, Guillaume; Gauthier, Paul; Buckley, Thomas N. ...
New phytologist,
December 2017, Letnik:
216, Številka:
4
Journal Article
Recenzirano
Odprti dostop
It has been 75 yr since leaf respiratory metabolism in the light (day respiration) was identified as a low-flux metabolic pathway that accompanies photosynthesis. In principle, it provides carbon ...backbones for nitrogen assimilation and evolves CO2 and thus impacts on plant carbon and nitrogen balances. However, for a long time, uncertainties have remained as to whether techniques used to measure day respiratory efflux were valid and whether day respiration responded to environmental gaseous conditions. In the past few years, significant advances have beenmade using carbon isotopes, ‘omics’ analyses and surveys of respiration rates in mesocosms or ecosystems. There is substantial evidence that day respiration should be viewed as a highly dynamic metabolic pathway that interacts with photosynthesis and photorespiration and responds to atmospheric CO2 mole fraction. The view of leaf day respiration as a constant and/or negligible parameter of net carbon exchange isnow outdated and it should now be regarded as a central actor of plant carbon-use efficiency.
Temperature-mediated changes in plant respiration (
R) are now accepted as an important component of the biosphere's response to global climate change. Here we discuss the underlying mechanisms ...responsible for the dynamic response of plant respiration to short and long-term temperature changes. The Q
10 is often assumed to be 2.0 (i.e.
R doubles per 10°C rise in temperature); however, the Q
10 is not constant (e.g. it declines near-linearly with increasing temperature). The temperature dependence of Q
10 is linked to shifts in the control exerted by maximum enzyme activity at low temperature and substrate limitations at high temperature. In the long term, acclimation of
R to temperature is common, in effect reducing the temperature sensitivity of
R to changes in thermal environment, with the temperature during plant development setting the maximal thermal acclimation of
R.
Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate (V
cmax). Estimating this parameter using A–C
i curves (net ...photosynthesis, A, vs intercellular CO2 concentration, C
i) is laborious, which limits availability of V
cmax data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO2 concentration (A
sat) measurements, from which V
cmax can be extracted using a ‘one-point method’.
We used a global dataset of A–C
i curves (564 species from 46 field sites, covering a range of plant functional types) to test the validity of an alternative approach to estimate V
cmax from A
sat via this ‘one-point method’.
If leaf respiration during the day (R
day) is known exactly, V
cmax can be estimated with an r
2 value of 0.98 and a root-mean-squared error (RMSE) of 8.19 μmolm−2 s−1. However, R
day typically must be estimated. Estimating R
day as 1.5% of V
cmax, we found that V
cmax could be estimated with an r
2 of 0.95 and an RMSE of 17.1 μmolm−2 s−1.
The one-point method provides a robust means to expand current databases of fieldmeasured V
cmax, giving new potential to improve vegetation models and quantify the environmental drivers of V
cmax variation.
Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate ...change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term temperature response, and even minor differences in the shape of the response curve can significantly impact estimates of ecosystem carbon release and/or storage. Given this, it is critical to establish whether there are predictable patterns in the shape of the respiration–temperature response curve, and thus in the intrinsic temperature sensitivity of respiration across the globe. Analyzing measurements in a comprehensive database for 231 species spanning 7 biomes, we demonstrate that temperature-dependent increases in leaf respiration do not follow a commonly used exponential function. Instead, we find a decelerating function as leaves warm, reflecting a declining sensitivity to higher temperatures that is remarkably uniform across all biomes and plant functional types. Such convergence in the temperature sensitivity of leaf respiration suggests that there are universally applicable controls on the temperature response of plant energy metabolism, such that a single new function can predict the temperature dependence of leaf respiration for global vegetation. This simple function enables straightforward description of plant respiration in the land-surface components of coupled earth system models. Our cross-biome analyses shows significant implications for such fluxes in cold climates, generally projecting lower values compared with previous estimates.
Understanding of the extent of acclimation of light‐saturated net photosynthesis (An) to temperature (T), and associated underlying mechanisms, remains limited. This is a key knowledge gap given the ...importance of thermal acclimation for plant functioning, both under current and future higher temperatures, limiting the accuracy and realism of Earth system model (ESM) predictions. Given this, we analysed and modelled T‐dependent changes in photosynthetic capacity in 10 wet‐forest tree species: six from temperate forests and four from tropical forests. Temperate and tropical species were each acclimated to three daytime growth temperatures (Tgrowth): temperate – 15, 20 and 25 °C; tropical – 25, 30 and 35 °C. CO2 response curves of An were used to model maximal rates of RuBP (ribulose‐1,5‐bisphosphate) carboxylation (Vcmax) and electron transport (Jmax) at each treatment's respective Tgrowth and at a common measurement T (25 °C). SDS‐PAGE gels were used to determine abundance of the CO2‐fixing enzyme, Rubisco. Leaf chlorophyll, nitrogen (N) and mass per unit leaf area (LMA) were also determined. For all species and Tgrowth, An at current atmospheric CO2 partial pressure was Rubisco‐limited. Across all species, LMA decreased with increasing Tgrowth. Similarly, area‐based rates of Vcmax at a measurement T of 25 °C (Vcmax25) linearly declined with increasing Tgrowth, linked to a concomitant decline in total leaf protein per unit leaf area and Rubisco as a percentage of leaf N. The decline in Rubisco constrained Vcmax and An for leaves developed at higher Tgrowth and resulted in poor predictions of photosynthesis by currently widely used models that do not account for Tgrowth‐mediated changes in Rubisco abundance that underpin the thermal acclimation response of photosynthesis in wet‐forest tree species. A new model is proposed that accounts for the effect of Tgrowth‐mediated declines in Vcmax25 on An, complementing current photosynthetic thermal acclimation models that do not account for T sensitivity of Vcmax25.
We analysed and modelled temperature‐dependent changes in photosynthetic capacity in 10 wet‐forest tree species; six from temperate forests and four from tropical forests. Area‐based rates of photosynthetic apacity (Vcmax) linearly declined with increasing growth temperature, linked to a concomitant decline in total leaf protein per unit leaf area and Rubisco as a percentage of leaf nitrogen. A new model is proposed that accounts for the effect of growth temperature‐mediated declines in Vcmax on photosynthesis.
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