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Are needles of Pinus pinaster more vulnerable to xylem embolism than branches? New insights from X‐ray computed tomography
Author(s) -
Bouche Pauline S.,
Delzon Sylvain,
Choat Brendan,
Badel Eric,
Brodribb Timothy J.,
Burlett Regis,
Cochard Hervé,
CharraVaskou Katline,
Lavigne Bruno,
Li Shan,
Mayr Stefan,
Morris Hugh,
TorresRuiz José M.,
Zufferey Vivian,
Jansen Steven
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.12680
Subject(s) - xylem , tracheid , pinus pinaster , context (archaeology) , pinus <genus> , computed tomography , anatomy , botany , biology , medicine , radiology , paleontology
Plants can be highly segmented organisms with an independently redundant design of organs. In the context of plant hydraulics, leaves may be less embolism resistant than stems, allowing hydraulic failure to be restricted to distal organs that can be readily replaced. We quantified drought‐induced embolism in needles and stems of Pinus pinaster using high‐resolution computed tomography (HRCT). HRCT observations of needles were compared with the rehydration kinetics method to estimate the contribution of extra‐xylary pathways to declining hydraulic conductance. High‐resolution computed tomography images indicated that the pressure inducing 50% of embolized tracheids was similar between needle and stem xylem ( P 50 needle xylem = −3.62 MPa, P 50 stem xylem = −3.88 MPa). Tracheids in both organs showed no difference in torus overlap of bordered pits. However, estimations of the pressure inducing 50% loss of hydraulic conductance at the whole needle level by the rehydration kinetics method were significantly higher ( P 50 needle = −1.71 MPa) than P 50 needle xylem derived from HRCT. The vulnerability segmentation hypothesis appears to be valid only when considering hydraulic failure at the entire needle level, including extra‐xylary pathways. Our findings suggest that native embolism in needles is limited and highlight the importance of imaging techniques for vulnerability curves.