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Grapevine petioles are more sensitive to drought induced embolism than stems: evidence from in vivo MRI and microcomputed tomography observations of hydraulic vulnerability segmentation
Author(s) -
Hochberg Uri,
Albuquerque Caetano,
Rachmilevitch Shimon,
Cochard Herve,
DavidSchwartz Rakefet,
Brodersen Craig R.,
McElrone Andrew,
Windt Carel W.
Publication year - 2016
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/pce.12688
Subject(s) - xylem , petiole (insect anatomy) , hydraulic conductivity , in vivo , vitis vinifera , magnetic resonance imaging , water stress , water transport , drought stress , embolism , vascular bundle , biology , anatomy , horticulture , medicine , botany , radiology , geology , water flow , surgery , soil science , ecology , hymenoptera , microbiology and biotechnology , soil water
The ‘hydraulic vulnerability segmentation’ hypothesis predicts that expendable distal organs are more susceptible to water stress‐induced embolism than the main stem of the plant. In the current work, we present the first in vivo visualization of this phenomenon. In two separate experiments, using magnetic resonance imaging or synchrotron‐based microcomputed tomography, grapevines ( Vitis vinifera ) were dehydrated while simultaneously scanning the main stems and petioles for the occurrence of emboli at different xylem pressures (Ψ x ). Magnetic resonance imaging revealed that 50% of the conductive xylem area of the petioles was embolized at a Ψ x of −1.54 MPa, whereas the stems did not reach similar losses until −1.9 MPa. Microcomputed tomography confirmed these findings, showing that approximately half the vessels in the petioles were embolized at a Ψ x of −1.6 MPa, whereas only few were embolized in the stems. Petioles were shown to be more resistant to water stress‐induced embolism than previously measured with invasive hydraulic methods. The results provide the first direct evidence for the hydraulic vulnerability segmentation hypothesis and highlight its importance in grapevine responses to severe water stress. Additionally, these data suggest that air entry through the petiole into the stem is unlikely in grapevines during drought.