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Title:   Author  item
                                            LEE, ERIC - University Of Californiaitem
                                            MATTHEWS, MARK - University Of Californiaitem
                                            McElrone, Andrewitem
                                            PHILLIPS, RONALD - University Of Californiaitem
                                            SHACKEL, KENNETH - University Of Californiaitem
                                            BRODERSEN, CRAIG - University Of California
  Submitted to: Journal of Theoretical Biology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 5/23/2013
                                    Publication  Date: 6/4/2013
                                    Citation: Lee, E.F., Matthews, M.A., Mcelrone, A.J., Phillips, R.J., Shackel, K.A., Brodersen, C.R. 2013. Analysis of HRCT-derived xylem network reveals reverse flow in some vessels. Journal of Theoretical Biology. 333:146-155.Interpretive Summary: In order to better understand the dynamics of water transport within grapevine xylem, we used data generated from advanced visualization techniques (CT scans) to build a model that simulates flow based on actual anatomical data. These efforts revealed that water can actually flow in the opposite direction (i.e. towards the roots) when the bulk of water is flowing strongly towards the leaves.  This mechanism helps to partially explain how pathogens (like Xylella fastidiosa that cause Pierce’s disease in grapevines) could move against the flow of water in host plant vasculature.  We also built a life sized model to simulate and provided a supplemental movie to the journal to clearer illustrate this reverse flow mechanism.
                                Technical Abstract: Flow in xylem vessels is modeled based on constructions of three dimensional xylem networks derived from High Resolution Computed Tomography (HRCT) images of grapevine (Vitis vinifera) stems. Flow in 6-14% of the vessels was found to be oriented in the opposite direction to the bulk flow under normal transpiration conditions. Based on the calculated flow rates in the xylem network, the downward spread of Xylella fastidiosa bacteria in grape stems was modeled, and reverse flow was shown to provide an additional mechanism for the movement of bacteria to the trunk of grapevine.


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