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Natale S, Peralta Ogorek LL, Caracciolo L, Morosinotto T, van Amerongen H, Casolo V, Pedersen O, Nardini A. Net O 2 exchange rates under dark and light conditions across different stem compartments. THE NEW PHYTOLOGIST 2024; 243:72-81. [PMID: 38703003 DOI: 10.1111/nph.19782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 04/02/2024] [Indexed: 05/06/2024]
Abstract
Woody plants display some photosynthetic activity in stems, but the biological role of stem photosynthesis and the specific contributions of bark and wood to carbon uptake and oxygen evolution remain poorly understood. We aimed to elucidate the functional characteristics of chloroplasts in stems of different ages in Fraxinus ornus. Our investigation employed diverse experimental approaches, including microsensor technology to assess oxygen production rates in whole stem, bark, and wood separately. Additionally, we utilized fluorescence lifetime imaging microscopy (FLIM) to characterize the relative abundance of photosystems I and II (PSI : PSII chlorophyll ratio) in bark and wood. Our findings revealed light-induced increases in O2 production in whole stem, bark, and wood. We present the radial profile of O2 production in F. ornus stems, demonstrating the capability of stem chloroplasts to perform light-dependent electron transport. Younger stems exhibited higher light-induced O2 production and dark respiration rates than older ones. While bark emerged as the primary contributor to net O2 production under light conditions, our data underscored that wood chloroplasts are also photosynthetically active. The FLIM analysis unveiled a lower PSI abundance in wood than in bark, suggesting stem chloroplasts are not only active but also acclimate to the spectral composition of light reaching inner compartments.
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Affiliation(s)
- Sara Natale
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy
- Dipartimento di Biologia, Università di Padova, Via Ugo Bassi 58B, Padova, 35121, Italy
| | - Lucas Léon Peralta Ogorek
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, Copenhagen, 2100, Denmark
- School of Biosciences, Sutton Bonington Campus, University of Nottingham, Loughborough, LE12 5RD, UK
| | - Ludovico Caracciolo
- Laboratory of Biophysics, Wageningen University & Research, PO Box 8128, 6700 ET, Wageningen, the Netherlands
| | - Tomas Morosinotto
- Dipartimento di Biologia, Università di Padova, Via Ugo Bassi 58B, Padova, 35121, Italy
| | - Herbert van Amerongen
- Laboratory of Biophysics, Wageningen University & Research, PO Box 8128, 6700 ET, Wageningen, the Netherlands
- MicroSpectroscopy Research Facility at Wageningen University & Research, Stippeneng 4, 6708 WE, Wageningen, the Netherlands
| | - Valentino Casolo
- Dipartimento di Scienze Agroalimentari, Ambientali e Animali, Università di Udine, Sezione di Biologia Vegetale, Via delle Scienze 91, Udine, 33100, Italy
| | - Ole Pedersen
- The Freshwater Biological Laboratory, Department of Biology, University of Copenhagen, Universitetsparken 4, Copenhagen, 2100, Denmark
- School of Biological Sciences, The University of Western Australia, Perth, WA, 6009, Australia
| | - Andrea Nardini
- Dipartimento di Scienze della Vita, Università di Trieste, Via L. Giorgieri 10, Trieste, 34127, Italy
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Salomón RL, Helm J, Gessler A, Grams TEE, Hilman B, Muhr J, Steppe K, Wittmann C, Hartmann H. The quandary of sources and sinks of CO2 efflux in tree stems-new insights and future directions. TREE PHYSIOLOGY 2024; 44:tpad157. [PMID: 38214910 DOI: 10.1093/treephys/tpad157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 12/12/2023] [Indexed: 01/13/2024]
Abstract
Stem respiration (RS) substantially contributes to the return of photo assimilated carbon to the atmosphere and, thus, to the tree and ecosystem carbon balance. Stem CO2 efflux (ECO2) is often used as a proxy for RS. However, this metric has often been challenged because of the uncertain origin of CO2 emitted from the stem due to post-respiratory processes. In this Insight, we (i) describe processes affecting the quantification of RS, (ii) review common methodological approaches to quantify and model RS and (iii) develop a research agenda to fill the most relevant knowledge gaps that we identified. Dissolution, transport and accumulation of respired CO2 away from its production site, reassimilation of respired CO2 via stem photosynthesis and the enzyme phosphoenolpyruvate carboxylase, axial CO2 diffusion in the gas phase, shifts in the respiratory substrate and non-respiratory oxygen (O2) consumption are the most relevant processes causing divergence between RS and measured stem gas exchange (ECO2 or O2 influx, IO2). Two common methodological approaches to estimate RS, namely the CO2 mass balance approach and the O2 consumption technique, circumvent some of these processes but have yielded inconsistent results regarding the fate of respired CO2. Stem respiration modelling has recently progressed at the organ and tree levels. However, its implementation in large-scale models, commonly operated from a source-driven perspective, is unlikely to reflect adequate mechanisms. Finally, we propose hypotheses and approaches to advance the knowledge of the stem carbon balance, the role of sap pH on RS, the reassimilation of respired CO2, RS upscaling procedures, large-scale RS modelling and shifts in respiratory metabolism during environmental stress.
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Affiliation(s)
- Roberto L Salomón
- Universidad Politécnica de Madrid (UPM), Departamento de Sistemas y Recursos Naturales, Research Group FORESCENT, Antonio Novais 10, 28040, Madrid, Spain
- Department of Plants and Crops, Laboratory of Plant Ecology, Ghent University, Faculty of Bioscience Engineering, Coupure Links 653, 9000 Ghent, Belgium
| | - Juliane Helm
- Max-Planck-Institute for Biogeochemistry, Biogeochemical Processes, Hans-Knöll-Str. 10, 07743 Jena, Germany
- Department of Environmental Sciences - Botany, Basel University, Schönbeinstr. 6, Basel CH-4056, Switzerland
| | - Arthur Gessler
- Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zurcherstrasse 111, 8903 Birmensdorf, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zürich, Rämistrasse 101, 8902 Zurich, Switzerland
| | - Thorsten E E Grams
- Technical University of Munich, Ecophysiology of Plants, Land Surface - Atmosphere Interactions, Von-Carlowitz-Platz 2, 85354 Freising, Germany
| | - Boaz Hilman
- Max-Planck-Institute for Biogeochemistry, Biogeochemical Processes, Hans-Knöll-Str. 10, 07743 Jena, Germany
| | - Jan Muhr
- Department of Forest Botany and Tree Physiology, Laboratory for Radioisotopes, Georg-August Universität Göttingen, Büsgenweg 2, 37077 Göttingen, Germany
| | - Kathy Steppe
- Department of Plants and Crops, Laboratory of Plant Ecology, Ghent University, Faculty of Bioscience Engineering, Coupure Links 653, 9000 Ghent, Belgium
| | - Christiane Wittmann
- Faculty of Biology, Botanical Garden, University of Duisburg-Essen, Universitätsstrasse 5, 45117 Essen, Germany
| | - Henrik Hartmann
- Max-Planck-Institute for Biogeochemistry, Biogeochemical Processes, Hans-Knöll-Str. 10, 07743 Jena, Germany
- Institute for Forest Protection, Julius Kühn Institute Federal Research Centre for Cultivated Plants, Erwin-Baur-Straße 27, 06484 Quedlinburg, Germany
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3
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Jardine KJ, Lei J, Som S, Souza D, Clendinen CS, Mehta H, Handakumbura P, Bill M, Young RP. Light-Dependence of Formate (C1) and Acetate (C2) Transport and Oxidation in Poplar Trees. PLANTS 2022; 11:plants11162080. [PMID: 36015384 PMCID: PMC9413118 DOI: 10.3390/plants11162080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/05/2022] [Accepted: 08/05/2022] [Indexed: 11/16/2022]
Abstract
Although apparent light inhibition of leaf day respiration is a widespread reported phenomenon, the mechanisms involved, including utilization of alternate respiratory pathways and substrates and light inhibition of TCA cycle enzymes are under active investigation. Recently, acetate fermentation was highlighted as a key drought survival strategy mediated through protein acetylation and jasmonate signaling. Here, we evaluate the light-dependence of acetate transport and assimilation in Populus trichocarpa trees using the dynamic xylem solution injection (DXSI) method developed here for continuous studies of C1 and C2 organic acid transport and light-dependent metabolism. Over 7 days, 1.0 L of [13C]formate and [13C2]acetate solutions were delivered to the stem base of 2-year old potted poplar trees, while continuous diurnal observations were made in the canopy of CO2, H2O, and isoprene gas exchange together with δ13CO2. Stem base injection of 10 mM [13C2]acetate induced an overall pattern of canopy branch headspace 13CO2 enrichment (δ13CO2 +27‰) with a diurnal structure in δ13CO2 reaching a mid-day minimum followed by a maximum shortly after darkening where δ13CO2 values rapidly increased up to +12‰. In contrast, 50 mM injections of [13C]formate were required to reach similar δ13CO2 enrichment levels in the canopy with δ13CO2 following diurnal patterns of transpiration. Illuminated leaves of detached poplar branches pretreated with 10 mM [13C2]acetate showed lower δ13CO2 (+20‰) compared to leaves treated with 10 mM [13C]formate (+320‰), the opposite pattern observed at the whole plant scale. Following dark/light cycles at the leaf-scale, rapid, strong, and reversible enhancements in headspace δ13CO2 by up to +60‰ were observed in [13C2]acetate-treated leaves which showed enhanced dihydrojasmonic acid and TCA cycle intermediate concentrations. The results are consistent with acetate in the transpiration stream as an effective activator of the jasmonate signaling pathway and respiratory substrate. The shorter lifetime of formate relative to acetate in the transpiration stream suggests rapid formate oxidation to CO2 during transport to the canopy. In contrast, acetate is efficiently transported to the canopy where an increased allocation towards mitochondrial dark respiration occurs at night. The results highlight the potential for an effective integration of acetate into glyoxylate and TCA cycles and the light-inhibition of citrate synthase as a potential regulatory mechanism controlling the diurnal allocation of acetate between anabolic and catabolic processes.
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Affiliation(s)
- Kolby J. Jardine
- Lawrence Berkeley National Laboratory, Climate and Ecosystem Science Division, Berkeley, CA 94720, USA
- Correspondence:
| | - Joseph Lei
- Lawrence Berkeley National Laboratory, Climate and Ecosystem Science Division, Berkeley, CA 94720, USA
| | - Suman Som
- Lawrence Berkeley National Laboratory, Climate and Ecosystem Science Division, Berkeley, CA 94720, USA
| | - Daisy Souza
- Forest Management Laboratory, National Institute for Amazon Research, Manaus 69067-375, Brazil
| | - Chaevien S. Clendinen
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Hardeep Mehta
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Pubudu Handakumbura
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA
| | - Markus Bill
- Lawrence Berkeley National Laboratory, Climate and Ecosystem Science Division, Berkeley, CA 94720, USA
| | - Robert P. Young
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA
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4
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Salomón RL, De Roo L, Bodé S, Boeckx P, Steppe K. Efflux and assimilation of xylem-transported CO 2 in stems and leaves of tree species with different wood anatomy. PLANT, CELL & ENVIRONMENT 2021; 44:3494-3508. [PMID: 33822389 DOI: 10.1111/pce.14062] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 03/30/2021] [Accepted: 03/31/2021] [Indexed: 06/12/2023]
Abstract
Determining the fate of CO2 respired in woody tissues is necessary to understand plant respiratory physiology and to evaluate CO2 recycling mechanisms. An aqueous 13 C-enriched CO2 solution was infused into the stem of 3-4 m tall trees to estimate efflux and assimilation of xylem-transported CO2 via cavity ring-down laser spectroscopy and isotope ratio mass spectrometry, respectively. Different tree locations (lower stem, upper stem and leafy shoots) and tissues (xylem, bark and leaves) were monitored in species with tracheid, diffuse- and ring-porous wood anatomy (cedar, maple and oak, respectively). Radial xylem CO2 diffusivity and xylem [CO2 ] were lower in cedar relative to maple and oak trees, thereby limiting label diffusion. Part of the labeled 13 CO2 was assimilated in cedar (8.7%) and oak (20.6%) trees, mostly in xylem and bark tissues of the stem, while limited solution uptake in maple trees hindered the detection of label assimilation. Little label reached foliar tissues, suggesting substantial label loss along the stem-branch transition following reductions in the radial diffusive pathway. Differences in respiration rates and radial xylem CO2 diffusivity (lower in conifer relative to angiosperm species) might reconcile discrepancies in efflux and assimilation of xylem-transported CO2 so far observed between taxonomic clades.
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Affiliation(s)
- Roberto Luis Salomón
- Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
- Grupo de Investigación Sistemas Naturales e Historia Forestal, Universidad Politécnica de Madrid, Madrid, Spain
| | - Linus De Roo
- Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Samuel Bodé
- Isotope Bioscience Laboratory-ISOFYS, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Pascal Boeckx
- Isotope Bioscience Laboratory-ISOFYS, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Kathy Steppe
- Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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5
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Aubrey DP, Teskey RO. Xylem transport of root-derived CO 2 caused a substantial underestimation of belowground respiration during a growing season. GLOBAL CHANGE BIOLOGY 2021; 27:2991-3000. [PMID: 33792118 DOI: 10.1111/gcb.15624] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 03/28/2021] [Indexed: 06/12/2023]
Abstract
Previous research has indicated that a potentially large portion of root-respired CO2 can move internally through tree xylem, but these reports are relatively scarce and have generally been limited to short observations. Our main objective was to provide a continuous estimate of the quantity and variability of root-respired CO2 that moves either internally through the xylem (FT ) or externally through the soil to the atmosphere (FS ) over most of a growing season. Nine trees were measured in a Populus deltoides stand for 129 days from early June to mid-October. We calculated FT as the product of sap flow and dissolved [CO2 ] in the xylem (i.e., [CO2 *]) and calculated FS using the [CO2 ] gradient method. During the study, stem and soil CO2 concentrations, temperature, and sap flow were measured continuously. We determined that FT accounted for 33% of daily total belowground CO2 flux (i.e., FS + FT ; FB ) during our observation period that spanned most of a growing season. Cumulative daily FT was lower than FS 74% of the time, equivalent to FS 26% of the time, and never exceeded FS . One-third of the total CO2 released by belowground respiration over most of the growing season in this forest stand followed the FT pathway rather than diffusing into the soil. The magnitude of FT indicates that measurements of FS alone substantially underestimate total belowground respiration in some forest ecosystems by systematically underestimating belowground autotrophic respiration. The variability in FT observed during the growing season demonstrated the importance of making long-term, high-frequency measurements of different flux pathways to better understand physiological and ecological processes and their implications to global change.
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Affiliation(s)
- Doug P Aubrey
- Savannah River Ecology Lab, University of Georgia, Aiken, SC, USA
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA
| | - Robert O Teskey
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA
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6
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Gimeno TE, Campany CE, Drake JE, Barton CVM, Tjoelker MG, Ubierna N, Marshall JD. Whole-tree mesophyll conductance reconciles isotopic and gas-exchange estimates of water-use efficiency. THE NEW PHYTOLOGIST 2021; 229:2535-2547. [PMID: 33217000 DOI: 10.1111/nph.17088] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 11/07/2020] [Indexed: 06/11/2023]
Abstract
Photosynthetic water-use efficiency (WUE) describes the link between terrestrial carbon (C) and water cycles. Estimates of intrinsic WUE (iWUE) from gas exchange and C isotopic composition (δ13 C) differ due to an internal conductance in the leaf mesophyll (gm ) that is variable and seldom computed. We present the first direct estimates of whole-tree gm , together with iWUE from whole-tree gas exchange and δ13 C of the phloem (δ13 Cph ). We measured gas exchange, online 13 C-discrimination, and δ13 Cph monthly throughout spring, summer, and autumn in Eucalyptus tereticornis grown in large whole-tree chambers. Six trees were grown at ambient temperatures and six at a 3°C warmer air temperature; a late-summer drought was also imposed. Drought reduced whole-tree gm . Warming had few direct effects, but amplified drought-induced reductions in whole-tree gm . Whole-tree gm was similar to leaf gm for these same trees. iWUE estimates from δ13 Cph agreed with iWUE from gas exchange, but only after incorporating gm . δ13 Cph was also correlated with whole-tree 13 C-discrimination, but offset by -2.5 ± 0.7‰, presumably due to post-photosynthetic fractionations. We conclude that δ13 Cph is a good proxy for whole-tree iWUE, with the caveats that post-photosynthetic fractionations and intrinsic variability of gm should be incorporated to provide reliable estimates of this trait in response to abiotic stress.
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Affiliation(s)
- Teresa E Gimeno
- Basque Centre for Climate Change (BC3), Leioa, 48940, Spain
- IKERBASQUE, Basque Foundation for Science, Bilbao, 48008, Spain
| | - Courtney E Campany
- Department of Biology, Shepherd University, Shepherdstown, WV, 25443, USA
| | - John E Drake
- Forest and Natural Resources Management, SUNY-ESF, Syracuse, NY, 132110, USA
| | - Craig V M Barton
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Mark G Tjoelker
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, 2751, Australia
| | - Nerea Ubierna
- Research School of Biology, The Australian National University, Acton, ACT, 2601, Australia
| | - John D Marshall
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogsmarksgränd 17, 907 36, Umeå, Sweden
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7
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Tarvainen L, Wallin G, Linder S, Näsholm T, Oren R, Ottosson Löfvenius M, Räntfors M, Tor-Ngern P, Marshall JD. Limited vertical CO2 transport in stems of mature boreal Pinus sylvestris trees. TREE PHYSIOLOGY 2021; 41:63-75. [PMID: 32864696 DOI: 10.1093/treephys/tpaa113] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Accepted: 08/25/2020] [Indexed: 05/14/2023]
Abstract
Several studies have suggested that CO2 transport in the transpiration stream can considerably bias estimates of root and stem respiration in ring-porous and diffuse-porous tree species. Whether this also happens in species with tracheid xylem anatomy and lower sap flow rates, such as conifers, is currently unclear. We infused 13C-labelled solution into the xylem near the base of two 90-year-old Pinus sylvestris L. trees. A custom-built gas exchange system and an online isotopic analyser were used to sample the CO2 efflux and its isotopic composition continuously from four positions along the bole and one upper canopy shoot in each tree. Phloem and needle tissue 13C enrichment was also evaluated at these positions. Most of the 13C label was lost by diffusion within a few metres of the infusion point indicating rapid CO2 loss during vertical xylem transport. No 13C enrichment was detected in the upper bole needle tissues. Furthermore, mass balance calculations showed that c. 97% of the locally respired CO2 diffused radially to the atmosphere. Our results support the notion that xylem CO2 transport is of limited magnitude in conifers. This implies that the concerns that stem transport of CO2 derived from root respiration biases chamber-based estimates of forest carbon cycling may be unwarranted for mature conifer stands.
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Affiliation(s)
- Lasse Tarvainen
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83 Umeå, Sweden
- Department of Biological and Environmental Sciences, University of Gothenburg, Carl Skottsbergs gata 22B, SE-405 30 Gothenburg, Sweden
- Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, Linnaeus väg 6, SE-901 87 Umeå, Sweden
| | - Göran Wallin
- Department of Biological and Environmental Sciences, University of Gothenburg, Carl Skottsbergs gata 22B, SE-405 30 Gothenburg, Sweden
| | - Sune Linder
- Southern Swedish Forest Research Centre, SLU, PO Box 49, SE-230 53, Alnarp, Sweden
| | - Torgny Näsholm
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83 Umeå, Sweden
| | - Ram Oren
- Nicholas School of the Environment, Duke University, Grainger Hall, 9 Circuit Drive, Box 90328, Durham, NC 27708-0328, USA
- Pratt School of Engineering, Duke University, 305 Teer Building, Box 90271, Durham, NC 27708-0271, USA
- Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, Box 27, FI-00014 Helsinki, Finland
| | - Mikaell Ottosson Löfvenius
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83 Umeå, Sweden
| | - Mats Räntfors
- Department of Biological and Environmental Sciences, University of Gothenburg, Carl Skottsbergs gata 22B, SE-405 30 Gothenburg, Sweden
| | - Pantana Tor-Ngern
- Department of Environmental Science, Faculty of Science, Chulalongkorn University, 254 Phayathai Rd, Wang Mai, Pathum Wan District, 10330 Bangkok, Thailand
- Environment, Health and Social Data Analytics Research Group, Chulalongkorn University, 254 Phayathai Rd, Wang Mai, Pathum Wan District, 10330 Bangkok, Thailand
| | - John D Marshall
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83 Umeå, Sweden
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Mincke J, Courtyn J, Vanhove C, Vandenberghe S, Steppe K. Studying in vivo dynamics of xylem-transported 11CO2 using positron emission tomography. TREE PHYSIOLOGY 2020; 40:1058-1070. [PMID: 32333788 DOI: 10.1093/treephys/tpaa048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 04/20/2020] [Indexed: 05/26/2023]
Abstract
Respired CO2 in woody tissues can build up in the xylem and dissolve in the sap solution to be transported through the plant. From the sap, a fraction of the CO2 can either be radially diffuse to the atmosphere or be assimilated in chloroplasts present in woody tissues. These processes occur simultaneously in stems and branches, making it difficult to study their specific dynamics. Therefore, an 11C-enriched aqueous solution was administered to young branches of Populus tremula L., which were subsequently imaged by positron emission tomography (PET). This approach allows in vivo visualization of the internal movement of CO2 inside branches at high spatial and temporal resolution, and enables direct measurement of the transport speed of xylem-transported CO2 (vCO2). Through compartmental modeling of the dynamic data obtained from the PET images, we (i) quantified vCO2 and (ii) proposed a new method to assess the fate of xylem-transported 11CO2 within the branches. It was found that a fraction of 0.49 min-1 of CO2 present in the xylem was transported upwards. A fraction of 0.38 min-1 diffused radially from the sap to the surrounding parenchyma and apoplastic spaces (CO2,PA) to be assimilated by woody tissue photosynthesis. Another 0.12 min-1 of the xylem-transported CO2 diffused to the atmosphere via efflux. The remaining CO2 (i.e., 0.01 min-1) was stored as CO2,PA, representing the build-up within parenchyma and apoplastic spaces to be assimilated or directed to the atmosphere. Here, we demonstrate the outstanding potential of 11CO2-based plant-PET in combination with compartmental modeling to advance our understanding of internal CO2 movement and the respiratory physiology within woody tissues.
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Affiliation(s)
- Jens Mincke
- Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
- MEDISIP-INFINITY, Department of Electronics and Information Systems, Faculty of Engineering and Architecture, Ghent University, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Jan Courtyn
- Medical Molecular Imaging and Therapy, Department of Radiology and Nuclear Medicine, Ghent University Hospital, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Christian Vanhove
- MEDISIP-INFINITY, Department of Electronics and Information Systems, Faculty of Engineering and Architecture, Ghent University, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Stefaan Vandenberghe
- MEDISIP-INFINITY, Department of Electronics and Information Systems, Faculty of Engineering and Architecture, Ghent University, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Kathy Steppe
- Laboratory of Plant Ecology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000 Ghent, Belgium
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Stutz SS, Hanson DT. Contribution and consequences of xylem-transported CO 2 assimilation for C 3 plants. THE NEW PHYTOLOGIST 2019; 223:1230-1240. [PMID: 31081546 DOI: 10.1111/nph.15907] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 05/03/2019] [Indexed: 06/09/2023]
Abstract
Traditionally, leaves were thought to be supplied with CO2 for photosynthesis by the atmosphere and respiration. Recent studies, however, have shown that the xylem also transports a significant amount of inorganic carbon into leaves through the bulk flow of water. However, little is known about the dynamics and proportion of xylem-transported CO2 that is assimilated, vs simply lost to transpiration. Cut leaves of Populus deltoides and Brassica napus were placed in either KCl or one of three [NaH13 CO3 ] solutions dissolved in water to simultaneously measure the assimilation and the efflux of xylem-transported CO2 exiting the leaf across light and CO2 response curves in real-time using a tunable diode laser absorption spectroscope. The rates of assimilation and efflux of xylem-transported CO2 increased with increasing xylem [13 CO2 *] and transpiration. Under saturating irradiance, rates of assimilation using xylem-transported CO2 accounted for c. 2.5% of the total assimilation in both species in the highest [13 CO2 *]. The majority of xylem-transported CO2 is assimilated, and efflux is small compared to respiration. Assimilation of xylem-transported CO2 comprises a small portion of total photosynthesis, but may be more important when CO2 is limiting.
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Affiliation(s)
- Samantha S Stutz
- Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA
| | - David T Hanson
- Department of Biology, University of New Mexico, Albuquerque, NM, 87131, USA
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10
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Salomón RL, De Roo L, Bodé S, Boeckx P, Steppe K. Isotope ratio laser spectroscopy to disentangle xylem-transported from locally respired CO2 in stem CO2 efflux. TREE PHYSIOLOGY 2019; 39:819-830. [PMID: 30726992 DOI: 10.1093/treephys/tpy152] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 12/18/2018] [Accepted: 01/02/2019] [Indexed: 06/09/2023]
Abstract
Respired CO2 in woody tissues radially diffuses to the atmosphere or it is transported upward with the transpiration stream, making the origin of CO2 in stem CO2 efflux (EA) uncertain, which may confound stem respiration (RS) estimates. An aqueous 13C-enriched solution was infused into stems of Populus tremula L. trees, and real-time measurements of 13C-CO2 and 12C-CO2 in EA were performed via Cavity Ring Down Laser Spectroscopy (CRDS). The contribution of locally respired CO2 (LCO2) and xylem-transported CO2 (TCO2) to EA was estimated from their different isotopic composition. Mean daily values of TCO2/EA ranged from 13% to 38%, evidencing the notable role that xylem CO2 transport plays in the assessment of stem respiration. Mean daily TCO2/EA did not differ between treatments of drought stress and light exclusion of woody tissues, but they showed different TCO2/EA dynamics on a sub-daily time scale. Sub-daily CO2 diffusion patterns were explained by a light-induced axial CO2 gradient ascribed to woody tissue photosynthesis, and the resistance to radial CO2 diffusion determined by bark water content. Here, we demonstrate the outstanding potential of CRDS paired with 13C-CO2 labelling to advance in the understanding of CO2 movement at the plant-atmosphere interface and the respiratory physiology in woody tissues.
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Affiliation(s)
- Roberto L Salomón
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Linus De Roo
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Samuel Bodé
- Isotope Bioscience Laboratory - ISOFYS, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
| | - Pascal Boeckx
- Isotope Bioscience Laboratory - ISOFYS, Faculty of Bioscience Engineering, Ghent University, Gent, Belgium
| | - Kathy Steppe
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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Wittmann C, Pfanz H. More than just CO 2 -recycling: corticular photosynthesis as a mechanism to reduce the risk of an energy crisis induced by low oxygen. THE NEW PHYTOLOGIST 2018; 219:551-564. [PMID: 29767842 DOI: 10.1111/nph.15198] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 03/19/2018] [Indexed: 06/08/2023]
Abstract
Reassimilation of internal CO2 via corticular photosynthesis (PScort ) has an important effect on the carbon economy of trees. However, little is known about its role as a source of O2 supply to the stem parenchyma and its implications in consumption and movement of O2 within trees. PScort of young Populus nigra (black poplar) trees was investigated by combining optical micro-optode measurements with monitoring of stem chlorophyll fluorescence. During times of zero sap flow in spring, stem oxygen concentrations (cO2 ) exhibited large temporal changes. In the sapwood, over 80% of diurnal changes in cO2 could be explained by respiration rates (Rd(mod) ). In the cortex, photosynthetic oxygen release during the day altered this relationship. With daytime illumination, oxygen levels in the cortex steadily increased from subambient and even exhibited a diel period of superoxia of up to 110% (% air sat.). By contrast, in the sapwood, cO2 never reached ambient levels; the diurnal oxygen deficit was up to 25% of air saturation. Our results confirm that PScort is not only a CO2 -recycling mechanism, it is also a mechanism to actively raise the cortical O2 concentration and counteract temporal/spatial hypoxia inside plant stems.
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Affiliation(s)
- Christiane Wittmann
- Department of Applied Botany and Volcano Biology, University of Duisburg-Essen, Essen, 45117, Germany
| | - Hardy Pfanz
- Department of Applied Botany and Volcano Biology, University of Duisburg-Essen, Essen, 45117, Germany
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Yang J, He Y, Aubrey DP, Zhuang Q, Teskey RO. Global patterns and predictors of stem CO2 efflux in forest ecosystems. GLOBAL CHANGE BIOLOGY 2016; 22:1433-1444. [PMID: 26667780 DOI: 10.1111/gcb.13188] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Revised: 10/30/2015] [Accepted: 11/29/2015] [Indexed: 06/05/2023]
Abstract
Stem CO2 efflux (ES) plays an important role in the carbon balance of forest ecosystems. However, its primary controls at the global scale are poorly understood and observation-based global estimates are lacking. We synthesized data from 121 published studies across global forest ecosystems and examined the relationships between annual ES and biotic and abiotic factors at individual, biome, and global scales, and developed a global gridded estimate of annual ES . We tested the following hypotheses: (1) Leaf area index (LAI) will be highly correlated with annual ES at biome and global scales; (2) there will be parallel patterns in stem and root CO2 effluxes (RA) in all forests; (3) annual ES will decline with forest age; and (4) LAI coupled with mean annual temperature (MAT) and mean annual precipitation (MAP) will be sufficient to predict annual ES across forests in different regions. Positive linear relationships were found between ES and LAI, as well as gross primary production (GPP), net primary production (NPP), wood NPP, soil CO2 efflux (RS), and RA . Annual ES was correlated with RA in temperate forests after controlling for GPP and MAT, suggesting other additional factors contributed to the relationship. Annual ES tended to decrease with stand age. Leaf area index, MAT and MAP, predicted 74% of variation in ES at global scales. Our statistical model estimated a global annual ES of 6.7 ± 1.1 Pg C yr(-1) over the period of 2000-2012 with little interannual variability. Modeled mean annual ES was 71 ± 43, 270 ± 103, and 420 ± 134 g C m(2) yr(-1) for boreal, temperate, and tropical forests, respectively. We recommend that future studies report ES at a standardized constant temperature, incorporate more manipulative treatments, such as fertilization and drought, and whenever possible, simultaneously measure both aboveground and belowground CO2 fluxes.
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Affiliation(s)
- Jinyan Yang
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA
| | - Yujie He
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 47907, USA
- Department of Earth System Science, University of California Irvine, Irvine, CA, 92697, USA
| | - Doug P Aubrey
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA
- Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, 29802, USA
| | - Qianlai Zhuang
- Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN, 47907, USA
- Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA
| | - Robert O Teskey
- Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30602, USA
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Bloemen J, Bauweraerts I, De Vos F, Vanhove C, Vandenberghe S, Boeckx P, Steppe K. Fate of xylem-transported 11C- and 13C-labeled CO2 in leaves of poplar. PHYSIOLOGIA PLANTARUM 2015; 153:555-64. [PMID: 25142926 DOI: 10.1111/ppl.12262] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 07/02/2014] [Indexed: 05/26/2023]
Abstract
In recent studies, assimilation of xylem-transported CO2 has gained considerable attention as a means of recycling respired CO2 in trees. However, we still lack a clear and detailed picture on the magnitude of xylem-transported CO2 assimilation, in particular within leaf tissues. To this end, detached poplar leaves (Populus × canadensis Moench 'Robusta') were allowed to take up a dissolved (13)CO2 label serving as a proxy of xylem-transported CO2 entering the leaf from the branch. The uptake rate of the (13)C was manipulated by altering the vapor pressure deficit (VPD) (0.84, 1.29 and 1.83 kPa). Highest tissue enrichments were observed under the highest VPD. Among tissues, highest enrichment was observed in the petiole and the veins, regardless of the VPD treatment. Analysis of non-labeled leaves showed that some (13)C diffused from the labeled leaves and was fixed in the mesophyll of the non-labeled leaves. However, (13)C leaf tissue enrichment analysis with elemental analysis coupled to isotope ratio mass spectrometry was limited in spatial resolution at the leaf tissue level. Therefore, (11)C-based CO2 labeling combined with positron autoradiography was used and showed a more detailed spatial distribution within a single tissue, in particular in secondary veins. Therefore, in addition to (13)C, (11) C-based autoradiography can be used to study the fate of xylem-transported CO2 at leaf level, allowing the acquisition of data at a yet unprecedented resolution.
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Affiliation(s)
- Jasper Bloemen
- Laboratory of Plant Ecology, Ghent University, 9000, Gent, Belgium
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Trumbore SE, Angert A, Kunert N, Muhr J, Chambers JQ. What's the flux? Unraveling how CO₂ fluxes from trees reflect underlying physiological processes. THE NEW PHYTOLOGIST 2013; 197:353-355. [PMID: 23253327 DOI: 10.1111/nph.12065] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Affiliation(s)
| | - Alon Angert
- The Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Norbert Kunert
- Max-Planck Institute for Biogeochemistry, Jena, 07745, Germany
| | - Jan Muhr
- Max-Planck Institute for Biogeochemistry, Jena, 07745, Germany
| | - Jeffrey Q Chambers
- Climate Sciences Department, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
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Bloemen J, McGuire MA, Aubrey DP, Teskey RO, Steppe K. Transport of root-respired CO₂ via the transpiration stream affects aboveground carbon assimilation and CO₂ efflux in trees. THE NEW PHYTOLOGIST 2013; 197:555-565. [PMID: 23057485 DOI: 10.1111/j.1469-8137.2012.04366.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 08/31/2012] [Indexed: 05/23/2023]
Abstract
Upward transport of CO₂ via the transpiration stream from belowground to aboveground tissues occurs in tree stems. Despite potentially important implications for our understanding of plant physiology, the fate of internally transported CO₂ derived from autotrophic respiratory processes remains unclear. We infused a ¹³CO₂-labeled aqueous solution into the base of 7-yr-old field-grown eastern cottonwood (Populus deltoides) trees to investigate the effect of xylem-transported CO₂ derived from the root system on aboveground carbon assimilation and CO₂ efflux. The ¹³C label was transported internally and detected throughout the tree. Up to 17% of the infused label was assimilated, while the remainder diffused to the atmosphere via stem and branch efflux. The largest amount of assimilated ¹³C was found in branch woody tissues, while only a small quantity was assimilated in the foliage. Petioles were more highly enriched in ¹³C than other leaf tissues. Our results confirm a recycling pathway for respired CO₂ and indicate that internal transport of CO₂ from the root system may confound the interpretation of efflux-based estimates of woody tissue respiration and patterns of carbohydrate allocation.
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Affiliation(s)
- Jasper Bloemen
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Gent, Belgium
| | - Mary Anne McGuire
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 East Green St, Athens, GA, 30602-2152, USA
| | - Doug P Aubrey
- Department of Biology, Georgia Southern University, PO Box 8042, Statesboro, GA, 30460-8042, USA
| | - Robert O Teskey
- Warnell School of Forestry and Natural Resources, University of Georgia, 180 East Green St, Athens, GA, 30602-2152, USA
| | - Kathy Steppe
- Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000, Gent, Belgium
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Churchland C, Weatherall A, Briones MJI, Grayston SJ. Stable-isotope labeling and probing of recent photosynthates into respired CO2, soil microbes and soil mesofauna using a xylem and phloem stem-injection technique on Sitka spruce (Picea sitchensis). RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2012; 26:2493-2501. [PMID: 23008066 DOI: 10.1002/rcm.6368] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
RATIONALE Here we report on the successful application of a novel stem-injection stable-isotope-labeling and probing technique in mature trees to trace the spatial and temporal distribution of rhizosphere carbon belowground. METHODS Three 22-year-old Sitka spruce trees were injected with 6.66 g of (13)C-labeled aspartic acid. Over the succeeding 30 days, soil CO(2) efflux, phospholipid fatty-acid (PLFA) microbial biomarkers and soil invertebrates (mites, collembolans and enchytraeids) were analyzed along a 50 m transect from each tree to determine the temporal and spatial patterns in the translocation of recently fixed photosynthates belowground. RESULTS Soil δ(13)CO(2) values peaked 13-23 days after injection, up to 5 m from the base of the injected tree and was, on average, 3.5‰ enriched in (13)C relative to the baseline. Fungal PLFA biomarkers peaked 2-4 days after stem-injection, up to 20 m from the base of the injected tree and were (13)C-enriched by up to 50‰. Significant (13)C enrichment in mites and enchytraeids occurred 4-6 days after injection (by, on average, 1.5‰). CONCLUSIONS Stem injection of large trees with (13)C-enriched compounds is a successful tool to trace C-translocation belowground. In particular, the significant (13)C enrichment of CO(2) and enchytraeids near the base of the tree and the significant (13)C enrichment of PLFAs up to 20 m away indicate that mature Sitka spruce (Picea sitchensis) have the capacity to support soil communities over large distances.
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Affiliation(s)
- Carolyn Churchland
- Belowground Ecosystem Group, Department of Forest Sciences, University of British Columbia, Vancouver, B.C., Canada.
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Epron D, Bahn M, Derrien D, Lattanzi FA, Pumpanen J, Gessler A, Högberg P, Maillard P, Dannoura M, Gérant D, Buchmann N. Pulse-labelling trees to study carbon allocation dynamics: a review of methods, current knowledge and future prospects. TREE PHYSIOLOGY 2012; 32:776-98. [PMID: 22700544 DOI: 10.1093/treephys/tps057] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Pulse-labelling of trees with stable or radioactive carbon (C) isotopes offers the unique opportunity to trace the fate of labelled CO(2) into the tree and its release to the soil and the atmosphere. Thus, pulse-labelling enables the quantification of C partitioning in forests and the assessment of the role of partitioning in tree growth, resource acquisition and C sequestration. However, this is associated with challenges as regards the choice of a tracer, the methods of tracing labelled C in tree and soil compartments and the quantitative analysis of C dynamics. Based on data from 47 studies, the rate of transfer differs between broadleaved and coniferous species and decreases as temperature and soil water content decrease. Labelled C is rapidly transferred belowground-within a few days or less-and this transfer is slowed down by drought. Half-lives of labelled C in phloem sap (transfer pool) and in mature leaves (source organs) are short, while those of sink organs (growing tissues, seasonal storage) are longer. (13)C measurements in respiratory efflux at high temporal resolution provide the best estimate of the mean residence times of C in respiratory substrate pools, and the best basis for compartmental modelling. Seasonal C dynamics and allocation patterns indicate that sink strength variations are important drivers for C fluxes. We propose a conceptual model for temperate and boreal trees, which considers the use of recently assimilated C versus stored C. We recommend best practices for designing and analysing pulse-labelling experiments, and identify several topics which we consider of prime importance for future research on C allocation in trees: (i) whole-tree C source-sink relations, (ii) C allocation to secondary metabolism, (iii) responses to environmental change, (iv) effects of seasonality versus phenology in and across biomes, and (v) carbon-nitrogen interactions. Substantial progress is expected from emerging technologies, but the largest challenge remains to carry out in situ whole-tree labelling experiments on mature trees to improve our understanding of the environmental and physiological controls on C allocation.
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Affiliation(s)
- Daniel Epron
- Université de Lorraine, UMR 1137, Ecologie et Ecophysiologie Forestières, Faculté des Sciences, F-54500 Vandoeuvre-les-Nancy, France.
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