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New Phytol. 2016 Jan;209(1):123-36. doi: 10.1111/nph.13646. Epub 2015 Sep 17.

Weak tradeoff between xylem safety and xylem-specific hydraulic efficiency across the world's woody plant species.

Author information

1
Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
2
USDA-ARS, Water Management Research, 2150 Center Ave, Build D, Suite 320, Fort Collins, CO, 80526, USA.
3
Institute of Systematic Botany and Ecology, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
4
Hawkesbury Institute for the Environment, Western Sydney University, Richmond, NSW, 2753, Australia.
5
Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2E3, Canada.
6
Department of Biology, California State University, Bakersfield, CA, 93311, USA.
7
Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, PA, 19041, USA.
8
School of Biological Sciences, University of Tasmania, Hobart, Tasmania, 7001, Australia.
9
Grupo de Estudios Biofísicos y Eco-fisiológicos (GEBEF), Universidad Nacional de la Patagonia San Juan Bosco, 9000, Comodoro Rivadavia, Argentina.
10
Plant Ecophysiology and Evolution Group, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, and College of Forestry, Guangxi University, Daxuedonglu 100, Nanning, Guangxi, 530004, China.
11
INRA, UMR547 PIAF, F-63100, Clermont-Ferrand, France.
12
Clermont Université, Université Blaise Pascal, UMR547 PIAF, F-63000, Clermont-Ferrand, France.
13
INRA, University of Bordeaux, UMR BIOGECO, F-33450, Talence, France.
14
Bordeaux Sciences AGRO, UMR1391 ISPA INRA, 1 Cours du général de Gaulle, 33175, Gradignan Cedex, France.
15
Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA.
16
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China.
17
School of Marine and Tropical Biology, James Cook University, Townsville, Qld, 4811, Australia.
18
Department of Forest, Rangeland and Fire Sciences, University of Idaho, Moscow, ID, 83844, USA.
19
Naturalis Biodiversity Center, Leiden University, PO Box 9517, 2300RA, Leiden, the Netherlands.
20
Department of Integrative Biology, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
21
CREAF, Cerdanyola del Vallès, E-08193, Barcelona, Spain.
22
ICREA at CREAF, Cerdanyola del Vallès, E-08193, Barcelona, Spain.
23
Department of Botany, University of Innsbruck, Sternwartestr. 15, 6020, Innsbruck, Austria.
24
Department of Botany, University of Wisconsin-Madison, Madison, WI, 53705, USA.
25
School of GeoSciences, University of Edinburgh, Crew Building, West Mains Road, Edinburgh, EH9 3FF, UK.
26
CSIRO Land and Water Flagship, Sandy Bay, Tasmania, 7005, Australia.
27
Dipartimento Scienze della Vita, Università Trieste, Via L. Giorgieri 10, 34127, Trieste, Italy.
28
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, 95064, USA.
29
Department of Biology, University of Utah, 257S 1400E, Salt Lake City, UT, 84112, USA.
30
Department of Biological Sciences, George Washington University, Science and Engineering Hall, 800 22nd Street NW, Suite 6000, Washington, DC, 20052, USA.

Abstract

The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem conduits, thus impeding sap transport to the leaves. A well-known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety-efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r(2)  < 0.086), no species had high efficiency and high safety, supporting the idea for a safety-efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r(2)  < 0.02 in most cases) with higher wood density, lower leaf- to sapwood-area and shorter stature. There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem.

KEYWORDS:

cavitation; embolism; hydraulic conductivity; mean annual precipitation; mean annual temperature; xylem

PMID:
26378984
DOI:
10.1111/nph.13646
[Indexed for MEDLINE]
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