|SCOFFONI, CHRISTINE - University Of California
|ALBUQUERQUE, CAETANO - University Of California
|BRODERSEN, CRAIG - Yale University
|TOWNES, SHATARA - University Of California
|JOHN, GRACE - University Of California
|COCHARD, HERVE - Inra, Génétique Animale Et Biologie Intégrative , Jouy-En-josas, France
|BUCKLEY, THOMAS - University Of Sydney
|SACK, LAWREN - University Of California
Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2016
Publication Date: 2/1/2017
Citation: Scoffoni, C., Albuquerque, C., Brodersen, C., Townes, S., John, G., Cochard, H., Buckley, T., McElrone, A.J., Sack, L. 2017. Leaf vein xylem conduit diameter influences susceptibility to embolism and hydraulic decline. New Phytologist. 213(3):1076-1092. https://doi.org/10.1111/nph.14256.
Interpretive Summary: Water scarcity threatens plant growth in natural and agricultural ecosystems worldwide. We studied how drought induced water stress alters the ability of leaf xylem to transport water. Using a variety of techniques including x-ray micro computed tomography, we found that leaf xylem becomes blocked by gas emboli under severe stress conditions and originated in the larger vessels contained in the midrib vein and petiole (i.e. leaf stalk) of several species.
Technical Abstract: Ecosystems worldwide are facing increasingly severe and prolonged droughts during which hydraulic failure from drought-induced embolism can lead to organ or whole plant death. Understanding the determinants of xylem failure across species is critical especially in leaves, the engine of plant growth. According to the vulnerability segmentation hypothesis, higher order veins, most terminal in the plant hydraulic system should be more susceptible to embolism, to protect the rest of the water transport system. Strongest vulnerability in the higher order veins would also be consistent with these experiencing the strongest tensions in the plant xylem during drought. To test this hypothesis, we combined X-ray micro-computed tomography imaging, hydraulic experiments, cross-sectional anatomy, and 3D physiological modelling to investigate how embolisms spread across petioles and vein orders during leaf dehydration and its relationship to conduit dimensions. Decline of leaf xylem hydraulic conductance (Kx) during dehydration was driven by embolism initiating in petioles and midribs, across species, Kx vulnerability was strongly correlated to midrib and petiole conduit dimensions. However, we found no relationship across species of Kx vulnerability with midrib or petiole diameter. Our results point to the critical importance of leaf xylem conduit diameter dimensions in maintaining xylem safety across species and habitats.