Plant hydraulic: new insights brought by HRCT

Recent advances in plant hydraulics have shed light on artifacts generated by hydraulic measurements, in interaction with wood anatomy (e.g. long-vesseled species). Such artifacts may have important implications in the assessment of plant drought vulnerabilities, and our understanding of the whole plant water balance. In this poster, we present how high resolution computed tomography (HRCT) -- a noninvasive method, which allows the detection of air and sap-filled xylem conducing elements in the wood of intact plants -- can provide non biased assessment of plants adaptation to drought: (i) we compared Vulnerability Curves to embolism (VC) assessed with classical hydraulic methods (Bench dehydration, Static centrifuge, Cavitron) and HRCT for species with different wood anatomies (i.e. ring-porous, diffuse porous, and tracheids). (ii) we compared safety margins for stomatal conductance and minimum water potential, based on HRCT VC (3 years-old intact seedlings), with previous safety margins for the well documented Mediterranean oak Q.ilex, (iii) we computed HRCT-based VC in two grapevine species (V. vinifera cv Cabernet- Sauvignon and V. riparia cv ‘Gloire de Montpellier’), and two organs (stems and petioles). Our results (i) confirmed the existence of strong bias in VC measurements obtained by classical methods in ring-porous species, (ii) demonstrated that the safety margin in Q.ilex is 2 to 4 MPa higher than previously described in the literature and (iii) highlighted the interspecific differences in stem drought vulnerability of grapevines, and assessed how this vulnerability could be distributed from the stem to the leaf. Altogether, these data demonstrate that HRCT is a useful tool to create a sound theory of plant hydraulic responses to drought