Plant-PET to investigate phloem vulnerability to drought in<i>Populus tremula</i>under changing climate regimes

Hubeau, Michiel; Mincke, Jens; Vanhove, Christian; Courtyn, Jan; Vandenberghe, Stefaan; Steppe, Kathy

doi:10.1093/treephys/tpy131

Cited by 16 publications

(27 citation statements)

References 70 publications

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“…The indirect empirical evidence of phloem transport failure comes from detection of severe shrinkage of phloem tissue prior to mortality , indirect measurement of phloem turgor loss (Salmon et al unpublished data), lack of labelled carbohydrate detection in phloem sap and stem respiration after pulse labelling with either 13 C (Dannoura et al 2019) or 11 C (Hubeau et al 2019), total depletion of carbohydrates in the roots of Norway spruce, while the canopy does not suffer reserve depletion (Hartmann et al 2013b).…”

Section: Is the Phloem Involved In Drought-induced Mortality?mentioning

confidence: 99%

“…Similarly, even if evidence of reduced carbohydrate pools e.g. in root tissue indicate slow or no phloem transport (Hartmann et al 2013a;Hartmann et al 2013b), more direct measurements based on the detection of labelled carbohydrates (Dannoura et al 2019;Hubeau et al 2019) are needed to confirm cessation of transport in a wider range of tree species, and the possible reasons for it. Intriguingly, in at least some species the effect of carbohydrate reserves on plant survival time (O'Brien et al 2014) could arise from varying access to reserves or varying phloem transport capacity among plants in the same environment ).…”

Section: Is the Phloem Involved In Drought-induced Mortality?mentioning

confidence: 99%

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Drought impacts on tree phloem: from cell-level responses to ecological significance

et al. 2019

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On-going climate change is increasing the risk of drought stress across large areas worldwide. Such drought events decrease ecosystem productivity and have been increasingly linked to tree mortality. Understanding how trees respond to water shortage is key to predicting the future of ecosystem functions. Phloem is at the core of the tree functions, moving resources such as non-structural carbohydrates, nutrients, and defence and information molecules across the whole plant. Phloem function and ability to transport resources is tightly controlled by the balance of carbon and water fluxes within the tree. As such, drought is expected to impact phloem function by decreasing the amount of available water and new photoassimilates. Yet, the effect of drought on the phloem has received surprisingly little attention in the last decades. Here we review existing knowledge on drought impacts on phloem transport from loading and unloading processes at cellular level to possible effects on long-distance transport and consequences to ecosystems via ecophysiological feedbacks. We also point to new research frontiers that need to be explored to improve our understanding of phloem function under drought. In particular, we show how phloem transport is affected differently by increasing drought intensity, from no response to a slowdown, and explore how severe drought might actually disrupt the phloem transport enough to threaten tree survival. Because transport of resources affects other organisms interacting with the tree, we also review the ecological consequences of phloem response to drought and especially predatory, mutualistic and competitive relations. Finally, as phloem is the main path for carbon from sources to sink, we show how drought can affect biogeochemical cycles through changes in phloem transport. Overall, existing knowledge is consistent with the hypotheses that phloem response to drought matters for understanding tree and ecosystem function. However, future research on a large range of species and ecosystems is urgently needed to gain a comprehensive understanding of the question.

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Section: Is the Phloem Involved In Drought-induced Mortality?mentioning

confidence: 99%

Section: Is the Phloem Involved In Drought-induced Mortality?mentioning

confidence: 99%

Drought impacts on tree phloem: from cell-level responses to ecological significance

et al. 2019

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“…Woody tissue photosynthetic rates range between 0.5 and 9 μmol CO 2 m −2 s −1 , with median values of 1.9 μmol CO 2 m −2 s −1 , and are generally lower than those in leaves, with maximum values being up to 75% of leaf photosynthesis (Ávila et al, ; Pfanz et al, ). Nevertheless, P wt is an important local carbon source for plant functioning, especially during drought stress when leaf photosynthesis and phloem transport are limited following stomatal closure and phloem dysfunction, respectively (Cernusak & Cheesman, ; Hubeau et al, ; Steppe, Sterck, & Deslauriers, ; Vandegehuchte et al, ).…”

Section: Introductionmentioning

confidence: 99%

Woody tissue photosynthesis reduces stem CO₂ efflux by half and remains unaffected by drought stress in young Populus tremula trees

Roo

Salomón

Steppe

2020

Plant Cell & Environment

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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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“…The potential of 11 C-positron emission tomography ( 11 C-PET) in plant studies remains largely untapped (Hubeau and Steppe, 2015). In past studies, 11 C-tracing has been used to study the transport speed of phytomolecules such as plant hormones (e.g., methyl jasmonate in Thorpe et al, 2007) and photoassimilates (Kikuchi et al, 2008), and 11 C-imaging has been used to visualize the phloem pathway for part of the plant (Kawachi et al, 2006;Jahnke et al, 2009;De Schepper et al, 2013;Hubeau et al, 2019a) or the entire plant (Kawachi et al, 2011). The acquired tracer profiles can be implemented in mathematical models to study sugar loading, sugar translocation, radial sugar leakage and sugar unloading (Bühler et al, 2011(Bühler et al, , 2014Minchin, 2012;Hubeau et al, 2019a).…”

Section: The Power Of Imaging 11 C-labeled Compounds In Plant Researchmentioning

confidence: 99%

“…Also, the 20 min halflife of 11 C limits its use to short-term processes, in contrast to the longer-lived carbon isotope 14 C (half-life of 5,730 years). On the positive side, 11 C-tracing allows an in vivo observation of tracer movement, which has led to significant research progress in topics such as phloem sectoriality (De Schepper et al, 2013), unloading characteristics (Jahnke et al, 2009), leakage-retrieval of photoassimilates along the transport pathway (Thorpe and Minchin, 1991), phloem functioning under changing climate regimes (Hubeau et al, 2019a) and carbon allocation to root and fruit parts (Jahnke et al, 2009;Wang et al, 2014). Importantly, non-invasive measurements allow dynamic aspects of a process to be studied, and 11 C therefore provides a powerful tool to reveal the mechanisms of physiological processes (Minchin and Thorpe, 2003;Jahnke et al, 2009;Bühler et al, 2011;Hubeau et al, 2019a).…”

Section: Introductionmentioning

confidence: 99%

High-Resolution in vivo Imaging of Xylem-Transported CO2 in Leaves Based on Real-Time 11C-Tracing

Hubeau

Thorpe

Mincke

et al. 2019

Front. For. Glob. Change

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Plant studies using the short-lived isotope 11 C to label photosynthate via atmospheric carbon dioxide (CO 2 ), have greatly advanced our knowledge about the allocation of recent photosynthate from leaves to sinks. However, a second source for photosynthesis is CO 2 in the transpiration stream, coming from respiration in plant tissues. Here, we use in vivo tracing of xylem-transported 11 CO 2 to increase our knowledge on whole plant carbon cycling. We developed a new method for in vivo tracing of xylem-transported CO 2 in excised poplar leaves using 11 C in combination with positron emission tomography (PET) and autoradiography. To show the applicability of both measurement techniques in visualizing and quantifying CO 2 transport dynamics, we administered the tracer via the cut petiole and manipulated the transport by excluding light or preventing transpiration. Irrespective of manipulation, some tracer was found in main and secondary veins, little of it was fixed in minor veins or mesophyll, while most of it diffused out the leaf. Transpiration, phloem loading and CO 2 recycling were identified as mechanisms that could be responsible for the transport of internal CO 2 . Both 11 C-PET and autoradiography can be successfully applied to study xylem-transported CO 2 , toward better understanding of leaf and plant carbon cycling, and its importance in different growing conditions.

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Plant-PET to investigate phloem vulnerability to drought inPopulus tremulaunder changing climate regimes

Cited by 16 publications

References 70 publications

Drought impacts on tree phloem: from cell-level responses to ecological significance

Drought impacts on tree phloem: from cell-level responses to ecological significance

Woody tissue photosynthesis reduces stem CO₂ efflux by half and remains unaffected by drought stress in young Populus tremula trees

High-Resolution in vivo Imaging of Xylem-Transported CO2 in Leaves Based on Real-Time 11C-Tracing

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Plant-PET to investigate phloem vulnerability to drought inPopulus tremulaunder changing climate regimes

Cited by 16 publications

References 70 publications

Drought impacts on tree phloem: from cell-level responses to ecological significance

Drought impacts on tree phloem: from cell-level responses to ecological significance

Woody tissue photosynthesis reduces stem CO2 efflux by half and remains unaffected by drought stress in young Populus tremula trees

High-Resolution in vivo Imaging of Xylem-Transported CO2 in Leaves Based on Real-Time 11C-Tracing

Contact Info

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Resources

About

Woody tissue photosynthesis reduces stem CO₂ efflux by half and remains unaffected by drought stress in young Populus tremula trees