Browsing by Subject "respiration"

Now showing 1 - 5 of 5
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    Convergent acclimation of leaf photosynthesis and respiration to prevailing ambient temperatures under current and warmer climates in Eucalyptus tereticornis
    (2016) Aspinwall, Michael J; Drake, John E; Campany, Courtney; Vårhammar, Angelica; Ghannoum, Oula; Tissue, David T; Reich, Peter B; Tjoelker, Mark G
    Understanding physiological acclimation of photosynthesis and respiration is important in elucidating the metabolic performance of trees in a changing climate. Does physiological acclimation to climate warming mirror acclimation to seasonal temperature changes? We grew Eucalyptus tereticornis trees in the field for 14 months inside 9-m tall whole-tree chambers tracking ambient air temperature (Tair) or ambient Tair + 3°C (i.e. ‘warmed’). We measured light- and CO2-saturated net photosynthesis (Amax) and night-time dark respiration (R) each month at 25°C to quantify acclimation. Tree growth was measured, and leaf nitrogen (N) and total nonstructural carbohydrate (TNC) concentrations were determined to investigate mechanisms of acclimation. Warming reduced Amax and R measured at 25°C compared to ambient-grown trees. Both traits also declined as mean daily Tair increased, and did so in a similar way across temperature treatments. Amax and R (at 25°C) both increased as TNC concentrations increased seasonally; these relationships appeared to arise from source–sink imbalances, suggesting potential substrate regulation of thermal acclimation. We found that photosynthesis and respiration each acclimated equivalently to experimental warming and seasonal temperature change of a similar magnitude, reflecting a common, nearly homeostatic constraint on leaf carbon exchange that will be important in governing tree responses to climate warming.
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    Data supporting "Adverse impacts of hypoxia on aquatic invertebrates: A meta-analysis"
    (2018-10-29) Galic, Nika; Hawkins, Tanner; Forbes, Valery E.; nika.galic001@gmail.com; Galic, Nika; Department of Ecology, Evolution, and Behavior
    The data set on responses of aquatic invertebrates to hypoxia was created by extracting and digitizing data from published studies. The raw data were scaled to controls (i.e., high levels of oxygen).
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    Lack of functional redundancy in the relationship between microbial diversity and ecosystem functioning
    (Wiley, 2016) Delgado‐Baquerizo, Manuel; Giaramida, Luca; Reich, Peter B; Khachane, Amit N; Hamonts, Kelly; Edwards, Christine; Lawton, Linda A; Singh, Brajesh K
    Biodiversity is declining world-wide with detrimental effects on ecosystems. However, we lack a quantitative understanding of the shape of the relationship between microbial biodiversity and ecosystem function (BEF). This limits our understanding of how microbial diversity depletion can impact key functions for human well-being, including pollutant detoxification. Three independent microcosm experiments were conducted to evaluate the direction (i.e. positive, negative or null) and the shape of the relationships between bacterial diversity and both broad (i.e. microbial respiration) and specialized (i.e. toxin degradation) functions in five Australian and two UK freshwater ecosystems using next-generation sequencing platforms. Reduced bacterial diversity, even after accounting for biomass, caused a decrease in broad (i.e. cumulative microbial respiration) and specialized (biodegradation of two important toxins) functions in all cases. Unlike the positive but decelerating BEF relationship observed most frequently in plants and animals, most evaluated functional measurements were related to bacterial diversity in a non-redundant fashion (e.g. exponentially and/or linearly). Synthesis. Our results suggest that there is a lack of functional redundancy in the relationship between bacterial diversity and ecosystem functioning; thus, the consequences of declining microbial diversity on ecosystem functioning and human welfare have likely been considerably underestimated.
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    Seasonal Metabolism Of Brown Adipose Tissue And Brain Mitochondria In The Thirteen-Lined Ground Squirrel (Ictidomys tridecemlineatus)
    (2015-08) Ballinger, Mallory
    During the hibernation season, thirteen-lined ground squirrels (Ictidomys tridecemlineatus) regularly cycle between bouts of torpor and interbout arousal (IBA). This presents a unique seasonal change in energy requirements in both the brain and brown adipose tissue (BAT). We hypothesized that brain and BAT mitochondria undergo a seasonal change in function to accommodate the variable energy demands of hibernation. To test this hypothesis, we examined mitochondrial bioenergetics of brain and BAT in thirteen-lined ground squirrels across five time points: summer, fall, torpor, IBA and spring. Through various molecular and functional analyses, we found significant increases in mitochondrial oxidative capacities of both brain and BAT during torpor and IBA. Overall, brain and BAT mitochondrial bioenergetics are not static across the year, and our studies suggest that these two tissues function efficiently during the hibernation season, when extreme physiological changes are occurring. These studies provide improved understanding of the overall energy requirements of a hibernator.
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    Why are non-photosynthetic tissues generally 13C enriched compared with leaves in C3 plants? Review and synthesis of current hypotheses
    (CSIRO, 2009) Cernusak, Lucas A; Tcherkez, Guillaume; Keitel, Claudia; Cornwell, William K; Santiago, Louis S; Knohl, Alexander; Barbour, Margaret M; Williams, David G; Reich, Peter B; Ellsworth, David S; Dawson, Todd E; Griffiths, Howard G; Farquhar, Graham D; Wright, Ian J
    Non-photosynthetic, or heterotrophic, tissues in C3 plants tend to be enriched in 13C compared with the leaves that supply them with photosynthate. This isotopic pattern has been observed for woody stems, roots, seeds and fruits, emerging leaves, and parasitic plants incapable of net CO2 fixation. Unlike in C3 plants, roots of herbaceous C4 plants are generally not 13C-enriched compared with leaves. We review six hypotheses aimed at explaining this isotopic pattern in C3 plants: (1) variation in biochemical composition of heterotrophic tissues compared with leaves; (2) seasonal separation of growth of leaves and heterotrophic tissues, with corresponding variation in photosynthetic discrimination against 13C; (3) differential use of day v. night sucrose between leaves and sink tissues, with day sucrose being relatively 13C-depleted and night sucrose 13C-enriched; (4) isotopic fractionation during dark respiration; (5) carbon fixation by PEP carboxylase; and (6) developmental variation in photosynthetic discrimination against 13C during leaf expansion. Although hypotheses (1) and (2) may contribute to the general pattern, they cannot explain all observations. Some evidence exists in support of hypotheses (3) through to (6), although for hypothesis (6) it is largely circumstantial. Hypothesis (3) provides a promising avenue for future research. Direct tests of these hypotheses should be carried out to provide insight into the mechanisms causing within-plant variation in carbon isotope composition.