Patterns and dynamics of canopy–root coupling in tropical tree saplings vary with light intensity but not with root depth

Israel Oren; Neringa Mannerheim; Rita Dumbur; Andreas Fangmeier; Nina Buchmann; José M. Grünzweig

doi:10.1111/nph.16153

Patterns and dynamics of canopy–root coupling in tropical tree saplings vary with light intensity but not with root depth

Israel Oren, Neringa Mannerheim, Rita Dumbur, Andreas Fangmeier, Nina Buchmann, José M. Grünzweig^*

^*Corresponding author for this work

Institute of Plant Sciences and Genetics in Agriculture

Research output: Contribution to journal › Article › peer-review

4 Scopus citations

Abstract

Carbon (C) dynamics in canopy and roots influence whole-tree carbon fluxes, but little is known about canopy regulation of tree-root activity. Here, the patterns and dynamics of canopy–root C coupling are assessed in tropical trees. Large aeroponics facility was used to study the root systems of Ceiba pentandra and Khaya anthotheca saplings directly at different light intensities. In Ceiba, root respiration (R_r) co-varied with photosynthesis (A_n) in large saplings (3-to-7-m canopy–root axis) at high-light, but showed no consistent pattern at low-light. At medium-light and in small saplings (c. 1-m axis), R_r tended to decrease transiently towards midday. Proximal roots had higher R_r and nonstructural carbohydrate concentrations than distal roots, but canopy–root coupling was unaffected by root location. In medium-sized Khaya, no R_r pattern was observed, and in both species, R_r was unrelated to temperature. The early-afternoon increase in R_r suggests that canopy–root coupling is based on mass flow of newly fixed C in the phloem, whereas the early-morning rise in R_r with A_n indicates an additional coupling signal that travels faster than the phloem sap. In large saplings and potentially also in higher trees, light and possibly additional environmental factors control the diurnal patterns of canopy–root coupling, irrespective of root location.

Original language	American English
Pages (from-to)	727-739
Number of pages	13
Journal	New Phytologist
Volume	225
Issue number	2
DOIs	https://doi.org/10.1111/nph.16153
State	Published - 1 Jan 2020

Bibliographical note

Funding Information:
The authors acknowledge Riccardo Valentini for raising the basic idea of this research, Ein Gedi Botanical Gardens for providing Ceiba pentandra seeds, Xavier Draye and Simone Fatichi for advice on the statistical models, Amram Eshel for sharing his expertise in aeroponics, and the student helpers who made the measurements possible. Financial support was granted by the Swiss National Foundation, the Ring Family Foundation, and the Ministry for Science, Research and the Arts of Baden-Württemberg (Rehovot-Hohenheim Partnership Program). IO was supported by the Robert H. Smith Prizes for Excellence in Agriculture.

Funding Information:
The authors acknowledge Riccardo Valentini for raising the basic idea of this research, Ein Gedi Botanical Gardens for providing seeds, Xavier Draye and Simone Fatichi for advice on the statistical models, Amram Eshel for sharing his expertise in aeroponics, and the student helpers who made the measurements possible. Financial support was granted by the Swiss National Foundation, the Ring Family Foundation, and the Ministry for Science, Research and the Arts of Baden‐Württemberg (Rehovot‐Hohenheim Partnership Program). IO was supported by the Robert H. Smith Prizes for Excellence in Agriculture. Ceiba pentandra

Publisher Copyright:
© 2019 The Authors. New Phytologist © 2019 New Phytologist Trust

Keywords

Ceiba pentandra
Khaya anthotheca
canopy–root coupling mechanisms
nonstructural carbohydrates
phloem sap flow velocity
photosynthesis
pressure concentration wave
root respiration

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10.1111/nph.16153

Cite this

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title = "Patterns and dynamics of canopy–root coupling in tropical tree saplings vary with light intensity but not with root depth",

abstract = "Carbon (C) dynamics in canopy and roots influence whole-tree carbon fluxes, but little is known about canopy regulation of tree-root activity. Here, the patterns and dynamics of canopy–root C coupling are assessed in tropical trees. Large aeroponics facility was used to study the root systems of Ceiba pentandra and Khaya anthotheca saplings directly at different light intensities. In Ceiba, root respiration (Rr) co-varied with photosynthesis (An) in large saplings (3-to-7-m canopy–root axis) at high-light, but showed no consistent pattern at low-light. At medium-light and in small saplings (c. 1-m axis), Rr tended to decrease transiently towards midday. Proximal roots had higher Rr and nonstructural carbohydrate concentrations than distal roots, but canopy–root coupling was unaffected by root location. In medium-sized Khaya, no Rr pattern was observed, and in both species, Rr was unrelated to temperature. The early-afternoon increase in Rr suggests that canopy–root coupling is based on mass flow of newly fixed C in the phloem, whereas the early-morning rise in Rr with An indicates an additional coupling signal that travels faster than the phloem sap. In large saplings and potentially also in higher trees, light and possibly additional environmental factors control the diurnal patterns of canopy–root coupling, irrespective of root location.",

keywords = "Ceiba pentandra, Khaya anthotheca, canopy–root coupling mechanisms, nonstructural carbohydrates, phloem sap flow velocity, photosynthesis, pressure concentration wave, root respiration",

author = "Israel Oren and Neringa Mannerheim and Rita Dumbur and Andreas Fangmeier and Nina Buchmann and Gr{\"u}nzweig, {Jos{\'e} M.}",

note = "Funding Information: The authors acknowledge Riccardo Valentini for raising the basic idea of this research, Ein Gedi Botanical Gardens for providing Ceiba pentandra seeds, Xavier Draye and Simone Fatichi for advice on the statistical models, Amram Eshel for sharing his expertise in aeroponics, and the student helpers who made the measurements possible. Financial support was granted by the Swiss National Foundation, the Ring Family Foundation, and the Ministry for Science, Research and the Arts of Baden-W{\"u}rttemberg (Rehovot-Hohenheim Partnership Program). IO was supported by the Robert H. Smith Prizes for Excellence in Agriculture. Funding Information: The authors acknowledge Riccardo Valentini for raising the basic idea of this research, Ein Gedi Botanical Gardens for providing seeds, Xavier Draye and Simone Fatichi for advice on the statistical models, Amram Eshel for sharing his expertise in aeroponics, and the student helpers who made the measurements possible. Financial support was granted by the Swiss National Foundation, the Ring Family Foundation, and the Ministry for Science, Research and the Arts of Baden‐W{\"u}rttemberg (Rehovot‐Hohenheim Partnership Program). IO was supported by the Robert H. Smith Prizes for Excellence in Agriculture. Ceiba pentandra Publisher Copyright: {\textcopyright} 2019 The Authors. New Phytologist {\textcopyright} 2019 New Phytologist Trust",

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AU - Oren, Israel

AU - Mannerheim, Neringa

AU - Dumbur, Rita

AU - Fangmeier, Andreas

AU - Buchmann, Nina

AU - Grünzweig, José M.

N1 - Funding Information: The authors acknowledge Riccardo Valentini for raising the basic idea of this research, Ein Gedi Botanical Gardens for providing Ceiba pentandra seeds, Xavier Draye and Simone Fatichi for advice on the statistical models, Amram Eshel for sharing his expertise in aeroponics, and the student helpers who made the measurements possible. Financial support was granted by the Swiss National Foundation, the Ring Family Foundation, and the Ministry for Science, Research and the Arts of Baden-Württemberg (Rehovot-Hohenheim Partnership Program). IO was supported by the Robert H. Smith Prizes for Excellence in Agriculture. Funding Information: The authors acknowledge Riccardo Valentini for raising the basic idea of this research, Ein Gedi Botanical Gardens for providing seeds, Xavier Draye and Simone Fatichi for advice on the statistical models, Amram Eshel for sharing his expertise in aeroponics, and the student helpers who made the measurements possible. Financial support was granted by the Swiss National Foundation, the Ring Family Foundation, and the Ministry for Science, Research and the Arts of Baden‐Württemberg (Rehovot‐Hohenheim Partnership Program). IO was supported by the Robert H. Smith Prizes for Excellence in Agriculture. Ceiba pentandra Publisher Copyright: © 2019 The Authors. New Phytologist © 2019 New Phytologist Trust

PY - 2020/1/1

Y1 - 2020/1/1

N2 - Carbon (C) dynamics in canopy and roots influence whole-tree carbon fluxes, but little is known about canopy regulation of tree-root activity. Here, the patterns and dynamics of canopy–root C coupling are assessed in tropical trees. Large aeroponics facility was used to study the root systems of Ceiba pentandra and Khaya anthotheca saplings directly at different light intensities. In Ceiba, root respiration (Rr) co-varied with photosynthesis (An) in large saplings (3-to-7-m canopy–root axis) at high-light, but showed no consistent pattern at low-light. At medium-light and in small saplings (c. 1-m axis), Rr tended to decrease transiently towards midday. Proximal roots had higher Rr and nonstructural carbohydrate concentrations than distal roots, but canopy–root coupling was unaffected by root location. In medium-sized Khaya, no Rr pattern was observed, and in both species, Rr was unrelated to temperature. The early-afternoon increase in Rr suggests that canopy–root coupling is based on mass flow of newly fixed C in the phloem, whereas the early-morning rise in Rr with An indicates an additional coupling signal that travels faster than the phloem sap. In large saplings and potentially also in higher trees, light and possibly additional environmental factors control the diurnal patterns of canopy–root coupling, irrespective of root location.

AB - Carbon (C) dynamics in canopy and roots influence whole-tree carbon fluxes, but little is known about canopy regulation of tree-root activity. Here, the patterns and dynamics of canopy–root C coupling are assessed in tropical trees. Large aeroponics facility was used to study the root systems of Ceiba pentandra and Khaya anthotheca saplings directly at different light intensities. In Ceiba, root respiration (Rr) co-varied with photosynthesis (An) in large saplings (3-to-7-m canopy–root axis) at high-light, but showed no consistent pattern at low-light. At medium-light and in small saplings (c. 1-m axis), Rr tended to decrease transiently towards midday. Proximal roots had higher Rr and nonstructural carbohydrate concentrations than distal roots, but canopy–root coupling was unaffected by root location. In medium-sized Khaya, no Rr pattern was observed, and in both species, Rr was unrelated to temperature. The early-afternoon increase in Rr suggests that canopy–root coupling is based on mass flow of newly fixed C in the phloem, whereas the early-morning rise in Rr with An indicates an additional coupling signal that travels faster than the phloem sap. In large saplings and potentially also in higher trees, light and possibly additional environmental factors control the diurnal patterns of canopy–root coupling, irrespective of root location.

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KW - Khaya anthotheca

KW - canopy–root coupling mechanisms

KW - nonstructural carbohydrates

KW - phloem sap flow velocity

KW - photosynthesis

KW - pressure concentration wave

KW - root respiration

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Patterns and dynamics of canopy–root coupling in tropical tree saplings vary with light intensity but not with root depth

Abstract

Bibliographical note

Keywords

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