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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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Tarvainen L, Henriksson N, Näsholm T, Marshall JD. Among-species variation in sap pH affects the xylem CO 2 transport potential in trees. THE NEW PHYTOLOGIST 2023; 238:926-931. [PMID: 36683449 DOI: 10.1111/nph.18768] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 12/26/2022] [Indexed: 06/17/2023]
Affiliation(s)
- Lasse Tarvainen
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 461, Gothenburg, SE-405 30, Sweden
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83, Umeå, Sweden
| | - Nils Henriksson
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83, Umeå, Sweden
| | - Torgny Näsholm
- Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), Skogmarksgränd, SE-901 83, Umeå, Sweden
| | - 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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Ye C, Zeng Q, Hu K, Fang D, Hölscher D, Du H, Shi Y, Zhou Y, Berninger F, Mei T, Zhou G. Partitioning of respired CO 2 in newly sprouted Moso bamboo culms. FRONTIERS IN PLANT SCIENCE 2023; 14:1154232. [PMID: 37152132 PMCID: PMC10158728 DOI: 10.3389/fpls.2023.1154232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 03/30/2023] [Indexed: 05/09/2023]
Abstract
Stem respiration (R s) plays a vital role in ecosystem carbon cycling. However, the measured efflux on the stem surface (E s) is not always in situ R s but only part of it. A previously proposed mass balance framework (MBF) attempted to explore the multiple partitioning pathways of R s, including sap-flow-transported and internal storage of R s, in addition to E s. This study proposed stem photosynthesis as an additional partitioning pathway to the MBF. Correspondingly, a double-chamber apparatus was designed and applied on newly sprouted Moso bamboo (Phyllostachys edulis) in leafless and leaved stages. R s of newly sprouted bamboo were twice as high in the leafless stage (7.41 ± 2.66 μmol m-2 s-1) than in the leaved stage (3.47 ± 2.43 μmol m-2 s-1). E s accounted for ~80% of R s, while sap flow may take away ~2% of R s in both leafless and leaved stages. Culm photosynthesis accounted for ~9% and 13% of R s, respectively. Carbon sequestration from culm photosynthesis accounted for approximately 2% of the aboveground bamboo biomass in the leafless stage. High culm photosynthesis but low sap flow during the leafless stage and vice versa during the leaved stage make bamboo an outstanding choice for exploring the MBF.
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Affiliation(s)
- Chongyu Ye
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
| | - Qiangfa Zeng
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
| | - Keda Hu
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
| | - Dongming Fang
- Jiyang College, Zhejiang A&F University, Zhuji, Zhejiang, China
| | - Dirk Hölscher
- Tropical Silviculture and Forest Ecology, University of Göttingen, Göttingen, Germany
| | - Huaqiang Du
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
| | - Yongjun Shi
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
| | - Yufeng Zhou
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
| | - Frank Berninger
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Tingting Mei
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
- *Correspondence: Tingting Mei, ; Guomo Zhou,
| | - Guomo Zhou
- State Key Laboratory of Subtropical Silviculture, Zhejiang A&F University, Lin’an, Zhejiang, China
- Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration of Zhejiang Province, Zhejiang A&F University, Lin’an, Zhejiang, China
- College of Environmental and Resource Sciences, Zhejiang A&F University, Lin’an, Zhejiang, China
- *Correspondence: Tingting Mei, ; Guomo Zhou,
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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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Stutz SS, Anderson J. Inside out: Measuring the effect of wood anatomy on the efflux and assimilation of xylem-transported CO 2. PLANT, CELL & ENVIRONMENT 2021; 44:3490-3493. [PMID: 34424562 DOI: 10.1111/pce.14172] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 07/22/2021] [Accepted: 08/06/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Samantha S Stutz
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Jeremiah Anderson
- Department of Environmental and Climate Sciences, Brookhaven National Laboratory, Upton, New York, USA
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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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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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De Roo L, Salomón RL, Steppe K. Woody tissue photosynthesis reduces stem CO 2 efflux by half and remains unaffected by drought stress in young Populus tremula trees. PLANT, CELL & ENVIRONMENT 2020; 43:981-991. [PMID: 31884680 DOI: 10.1111/pce.13711] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/19/2019] [Accepted: 12/21/2019] [Indexed: 06/10/2023]
Abstract
A substantial portion of locally respired CO2 in stems can be assimilated by chloroplast-containing tissues. Woody tissue photosynthesis (Pwt ) therefore plays a major role in the stem carbon balance. To study the impact of Pwt on stem carbon cycling along a gradient of water availability, stem CO2 efflux (EA ), xylem CO2 concentration ([CO2 ]), and xylem water potential (Ψxylem ) were measured in 4-year-old Populus tremula L. trees exposed to drought stress and different regimes of light exclusion of woody tissues. Under well-watered conditions, local Pwt decreased EA up to 30%. Axial CO2 diffusion (Dax ) induced by distant Pwt caused an additional decrease in EA of up to 25% and limited xylem [CO2 ] build-up. Under drought stress, absolute decreases in EA driven by Pwt remained stable, denoting that Pwt was not affected by drought. At the end of the dry period, when transpiration was low, local Pwt and Dax offset 20% and 10% of stem respiration on a daily basis, respectively. These results highlight (a) the importance of Pwt for an adequate interpretation of EA measurements and (b) homeostatic Pwt along a drought stress gradient, which might play a crucial role to fuel stem metabolism when leaf carbon uptake and phloem transport are limited.
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Affiliation(s)
- Linus De Roo
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Roberto Luis Salomón
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Kathy Steppe
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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Salomón RL, De Roo L, Oleksyn J, De Pauw DJW, Steppe K. TReSpire - a biophysical TRee Stem respiration model. THE NEW PHYTOLOGIST 2020; 225:2214-2230. [PMID: 31494939 DOI: 10.1111/nph.16174] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 08/29/2019] [Indexed: 06/10/2023]
Abstract
Mechanistic models of plant respiration remain poorly developed, especially in stems and woody tissues where measurements of CO2 efflux do not necessarily reflect local respiratory activity. We built a process-based model of stem respiration that couples water and carbon fluxes at the organ level (TReSpire). To this end, sap flow, stem diameter variations, xylem and soil water potential, stem temperature, stem CO2 efflux and nonstructural carbohydrates were measured in a maple tree, while xylem CO2 concentration and additional stem and xylem diameter variations were monitored in an ancillary tree for model validation. TReSpire realistically described: (1) turgor pressure to differentiate growing from nongrowing metabolism; (2) maintenance expenditures in xylem and outer tissues based on Arrhenius kinetics and nitrogen content; and (3) radial CO2 diffusivity and CO2 solubility and transport in the sap solution. Collinearity issues with phloem unloading rates and sugar-starch interconversion rates suggest parallel submodelling to close the stem carbon balance. TReSpire brings a breakthrough in the modelling of stem water and carbon fluxes at a detailed (hourly) temporal resolution. TReSpire is calibrated from a sink-driven perspective, and has potential to advance our understanding on stem growth dynamics, CO2 fluxes and underlying respiratory physiology across different species and phenological stages.
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Affiliation(s)
- Roberto L Salomón
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, Ghent, 9000, Belgium
| | - Linus De Roo
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, Ghent, 9000, Belgium
| | - Jacek Oleksyn
- Polish Academy of Sciences, Institute of Dendrology, Parkowa 5, Kórnik, PL-62-035, Poland
| | - Dirk J W De Pauw
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, Ghent, 9000, Belgium
| | - Kathy Steppe
- Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, Ghent, 9000, Belgium
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