Comparative anatomy vs mechanistic understanding: how to interpret the diameter-vulnerability link

IAWA Journal - KU Leuven/IAWA Journal, vol. 44, pp. 368–380

Abstract

Summary Results from comparative and ecological wood anatomy combined with a number of experimental studies on plant hydraulics have led to a pervasive and longstanding assumption that wider-diameter vessels are more vulnerable to drought-induced embolism than narrower vessels. Although we agree that wider vessels tend to be more vulnerable than narrower vessels within stems and within roots across most species, our current understanding of the diameter-vulnerability link does not offer a mechanistic explanation for why increased vessel diameter should consistently lead to greater vulnerability or vice versa. Causes of drought-induced embolism formation and spread likely operate at the nano-level, especially at gas-liquid-surfactant interfaces inside intervessel pit membranes. We evaluate here new perspectives on drought-induced embolism and its key anatomical and physico-chemical drivers, of which vessel diameter is one of the parameters involved, although its linkage to embolism vulnerability is likely indirect. As such, the diameter-vulnerability link does not imply that species with on average wider vessels are consistently more susceptible to drought-induced embolism compared to species with narrower vessels. Scientific priorities for future progress should focus on more accurate predictions of how water transport in plants is affected by drought, which requires a better mechanistic understanding of xylem network topology and biophysical processes at the nano-scale level in individual vessels that determine embolism formation and spread.

Authors 6

1. Frederic Lens Aachen Institute of Biology, Plant Sciences Naturalis Biodiversity Center

   Leiden University · Naturalis Biodiversity Center

   Affiliation as printed

   Institute of Biology, Plant Sciences, Leiden University, Sylviusweg 72, 2333 BE Leiden, The Netherlands

   Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The Netherlands

   Leiden University

2. Sean M. Gleason

   Agricultural Research Service · United States Department of Agriculture · Agricultural Research Service - Plains Area

   Affiliation as printed

   Water Management and Systems Research Unit, United States Department of Agriculture, Agricultural Research Service, Fort Collins, CO 80526, USA

   Agricultural Research Service

3. Giovanni Bortolami Aachen Naturalis Biodiversity Center

   Naturalis Biodiversity Center

   Affiliation as printed

   Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA Leiden, The Netherlands

4. Craig R. Brodersen

   Yale University

   Affiliation as printed

   School of the Environment, Yale University, New Haven, CT 06511, USA

   Yale University

5. Sylvain Delzon

   Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement · Université de Bordeaux · UMR BIOdiversity, GEnes & Communities

   Affiliation as printed

   INRAE, BIOGECO, University of Bordeaux, 33615 Pessac, France

   INRAE, BIOGECO

6. Steven Jansen

   Universität Ulm

   Affiliation as printed

   Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, D-89081, Ulm, Germany

   Ulm University