|Brodersen, Craig - University Of Florida|
|Choat, Brendan - Western Sydney University|
|Lee, Eric - University Of California|
|Shackel, Ken - University Of California|
|Matthews, Mark - University Of California|
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2013
Publication Date: 4/1/2013
Publication URL: http://www.plantphysiol.org/content/161/4/1820.full.pdf+html
Citation: Brodersen, C., Mcelrone, A.J., Choat, B., Lee, E., Shackel, K., Matthews, M. 2013. In vivo visualizations of drought-induced embol 35 ism spread in Vitis vinifera. Plant Physiology. 161(4):1820-1829.
Interpretive Summary: We used X-ray computed tomography (i.e. a type of CAT scan) to visualize the function of the water conducting tissue (xylem) of grapevines subjected to drought stress. Embolism started in all cases at the center of the stem and primarily spread outwards (similar to the spokes of a bicycle wheel). These data revealed in fine detail the pathways involved in vascular dysfunction induced by drought stress, and identified “xylem vessel relays” as an important component of this pathway- our group recently described this anatomical feature based on CT scan data.
Technical Abstract: Long distance water transport through plant xylem is vulnerable to hydraulic dysfunction during periods of increased tension on the xylem sap, often coinciding with drought. While the effects of local and systemic embolism on plant water transport and physiology are well documented, the spatial patterns of embolism formation and spread are not well understood. Using a recently developed non-destructive diagnostic imaging tool, high resolution X-ray computed tomography (HRCT), we documented the dynamics of drought-induced embolism in grapevine (Vitis vinifera) plants in vivo, producing the first three dimensional, high resolution, time-lapse observations of embolism spread. Embolisms formed first in the vessels surrounding the pith at stem water potentials of approximately -1.2 MPa in drought experiments. As stem water potential decreased, embolisms spread radially toward the epidermis within sectored vessel groupings via intervessel connections and conductive xylem relays, and infrequently (16 of 629 total connections) through lateral connections into adjacent vessel sectors. Theoretical loss of conductivity calculated from the HRCT images showed good agreement with previously published nuclear magnetic resonance imaging and hydraulic conductivity experiments also using V. vinifera. Overall, these data support a growing body of evidence that xylem organization is critically important to the isolation of drought-induced embolism spread, and confirm that air seeding through the pit membranes is the principle mechanism of embolism spread.