A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species

Daniel M. Johnson, Remi Wortemann, Katherine A. McCulloh, Lionel Jordan-Meille, Eric Ward, Jeffrey M. Warren, Sari Palmroth, Jean Christophe Domec

Research output: Contribution to journalArticlepeer-review

147 Scopus citations

Abstract

Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are nonredundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf and xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. This study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.

Original languageEnglish
Pages (from-to)983-993
Number of pages11
JournalTree Physiology
Volume36
Issue number8
DOIs
StatePublished - Aug 2016

Funding

This research was supported by NSF (IOS-1146746, NSF-IOS-1549971) and a grant from USDA-AFRI (#2012-00857). J.-C.D. and L.J.-M. acknowledge support from the French Research Agency (projects MACACC ANR-13-AGRO-0005 and MARIS ANR-14-CE03-0007) as well as the Jacques et Fran-çoise Lescouzères Foundation and ‘la forêt-école des Agreaux’.

FundersFunder number
USDA-AFRI

    Keywords

    • Cavitation
    • Drought
    • Embolism
    • Transpiration
    • Water relations

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