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Smith-Martin CM, Johnson KM, Urquhart S, Carins-Murphy MR, Rodriguez-Dominguez CM, Lucani C, Corso D, Choat B, Gauthey A, Perez-Martinez LV, McAdam SAM, Werden LK, Brodribb TJ. Increasing air-filled vessels has little influence on vulnerability to drought-induced embolism in two species with long maximum xylem vessel length but low vessel connectivity. TREE PHYSIOLOGY 2025; 45:tpaf041. [PMID: 40188479 DOI: 10.1093/treephys/tpaf041] [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: 07/31/2024] [Revised: 02/18/2025] [Accepted: 03/19/2025] [Indexed: 04/08/2025]
Abstract
Perennial woody plants accumulate native xylem embolisms over time. However, whether this makes the water transport system more vulnerable to drought-induced dysfunction as the percentage of gas-filled vessels increases is unclear. We tested whether increasing the proportion of open (air-filled) vessels changes the overall embolism vulnerability in stems of angiosperm species with long maximum vessel lengths but relatively low vessel connectivity. Using optical vulnerability curves, we measured xylem vulnerability of 57 branches ranging in length from ~ 10 to over 300 cm, from two adult trees (Acacia mearnsii De Wild. and Eucalyptus globulus Labill.) known to have long maximum vessel length (>75 cm) but low vessel connectivity. The fraction of open vessels at different branch lengths was estimated by staining open vessels under suction and with X-ray micro-computed tomography (μCT). To relate this to native field conditions, the percentage of pre-existing native embolisms was measured with μCT on a different set of branches. Our results show that even when a large proportion (> 25%) of open (air-filled) vessels are present, the xylem-embolism thresholds (water potential at 12% (P12), 50% (P50) and 88% (P88) embolized xylem area) resemble those of branches with no open vessels. Scanning of native embolism with μCT revealed 10% (E. globulus) and 20% (A. mearnsii) native embolism under natural conditions. We conclude that even when approximately one-quarter of vessels are air-filled, there is no discernable effect on the overall xylem vulnerability of stem segments with long vessels and low vessel connectivity. Xylem vulnerability to embolism among all the branches measured from each of the two trees was relatively homogeneous with a ~10-20% variation. Our findings also suggest that the presence of pre-existing native embolisms, at the percentages observed in the field (<25%), would not increase vulnerability to xylem embolism in these species with largely isolated individual xylem vessels.
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Affiliation(s)
- Chris M Smith-Martin
- Department of Plant and Microbial Biology, University of Minnesota, 1475 Gortner Ave. St Paul, MN 55108, USA
| | - Kate M Johnson
- Ecological and Forestry Applications Research Centre (CREAF), Campus de Bellaterra, Cerdanyola del Vallès, 08193, Spain
| | - Shelley Urquhart
- School of Natural Sciences, University of Tasmania, Private Bag 55, Tas, Hobart 7001 Tasmania, Australia
| | - Madeline R Carins-Murphy
- School of Natural Sciences, University of Tasmania, Private Bag 55, Tas, Hobart 7001 Tasmania, Australia
| | - Celia M Rodriguez-Dominguez
- Plant Ecophysiology and Irrigation (ECOVER) Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Avenida Reina Mercedes, 10, 41012 Sevilla, Spain
| | - Christopher Lucani
- School of Natural Sciences, University of Tasmania, Private Bag 55, Tas, Hobart 7001 Tasmania, Australia
| | - Déborah Corso
- School of Natural Sciences, University of Tasmania, Private Bag 55, Tas, Hobart 7001 Tasmania, Australia
| | - Brendan Choat
- Hawkesbury Institute for the Environment, Western Sydney University, Bourke St, Richmond, NSW 2753, Australia
| | - Alice Gauthey
- The Birmingham Institute of Forest Research (BIFoR), University of Birmingham, Edgbaston Birmingham, B15 2TT, UK
| | | | - Scott A M McAdam
- Department of Botany and Plant Pathology, Purdue Center for Plant Biology, Purdue University, 610 Purdue Mall, West Lafayette, IN 47907, USA
| | - Leland K Werden
- Institute of Integrative Biology, ETH Zürich (Swiss Federal Institute of Technology), Universitätstrasse 16, 8092 Zürich, Switzerland
| | - Timothy J Brodribb
- School of Natural Sciences, University of Tasmania, Private Bag 55, Tas, Hobart 7001 Tasmania, Australia
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Petit G. An appreciation of apex-to-base variation in xylem traits will lead to more precise understanding of xylem phenotypic plasticity. THE NEW PHYTOLOGIST 2024; 244:1175-1180. [PMID: 39262308 DOI: 10.1111/nph.20109] [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: 03/14/2024] [Accepted: 08/22/2024] [Indexed: 09/13/2024]
Abstract
Xylem air embolism is the primary cause of drought-related tree mortality. Phenotypic plasticity of xylem traits is key for species acclimation to environmental variability and evolution. It is widely believed that plants increase xylem embolism resistance in response to drought. However, I argue that this hypothesis, based on extensive literature, relies on sampling methods that overlook predictable anatomical patterns, potentially biasing our understanding of acclimation and adaptation strategies.
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Affiliation(s)
- Giai Petit
- Dipartimento Territorio e Sistemi Agro-Forestali, University of Padua, Viale dell'Università 16, 35020, Legnaro, PD, Italy
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Keiser L, Dollet B, Marmottant P. Embolism propagation in Adiantum leaves and in a biomimetic system with constrictions. J R Soc Interface 2024; 21:20240103. [PMID: 39140327 PMCID: PMC11323083 DOI: 10.1098/rsif.2024.0103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 04/12/2024] [Accepted: 06/04/2024] [Indexed: 08/15/2024] Open
Abstract
Drought poses a significant threat to forest survival worldwide by potentially generating air bubbles that obstruct sap transport within plants' hydraulic systems. However, the detailed mechanism of air entry and propagation at the scale of the veins remains elusive. Building upon a biomimetic model of leaf which we developed, we propose a direct comparison of the air embolism propagation in Adiantum (maidenhair fern) leaves, presented in Brodribb et al. (Brodribb TJ, Bienaimé D, Marmottant P. 2016 Revealing catastrophic failure of leaf networks under stress. Proc. Natl Acad. Sci. USA 113, 4865-4869 (doi:10.1073/pnas.1522569113)) and in our biomimetic leaves. In particular, we evidence that the jerky dynamics of the embolism propagation observed in Adiantum leaves can be recovered through the introduction of micrometric constrictions in the section of our biomimetic veins, mimicking the nanopores present in the bordered pit membranes in real leaves. We show that the intermittency in the propagation can be retrieved by a simple model coupling the variations of pressure induced by the constrictions and the variations of the volume of the compliant microchannels. Our study marks a step with the design of a biomimetic leaf that reproduces particular aspects of embolism propagation in real leaves, using a minimal set of controllable and readily tunable components. This biomimetic leaf constitutes a promising physical analogue and sets the stage for future enhancements to fully embody the unique physical features of embolizing real leaves.
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