Storage Compartments for Capillary Water Rarely Refill in an Intact Woody Plant  

Abstract

Water storage is thought to play an integral role in the maintenance of whole-plant water balance. The contribution of both living and dead cells to water storage can be derived from rehydration and water-release curves on excised plant material, but the underlying tissue-specific emptying/refilling dynamics remain unclear. Here, we used x-ray computed microtomography to characterize the refilling of xylem fibers, pith cells, and vessels under both excised and in vivo conditions in In excised stems supplied with water, water uptake exhibited a biphasic response curve, and x-ray computed microtomography images showed that high water storage capacitance was associated with fiber and pith refilling as driven by capillary forces: fibers refilled more rapidly than pith cells, while vessel refilling was minimal. In excised stems that were sealed, fiber and pith refilling was associated with vessel emptying, indicating a link between tissue connectivity and water storage. In contrast, refilling of fibers, pith cells, and vessels was negligible in intact saplings over two time scales, 24 h and 3 weeks. However, those compartments did refill slowly when the shoot was covered to prevent transpiration. Collectively, our data (1) provide direct evidence that storage compartments for capillary water refill in excised stems but rarely under in vivo conditions, (2) highlight that estimates of capacitance from excised samples should be interpreted with caution, as certain storage compartments may not be utilized in the intact plant, and (3) question the paradigm that fibers play a substantial role in daily discharge/recharge of stem capacitance in an intact tree.

Insights from in vivo micro‐CT analysis: testing the hydraulic vulnerability segmentation in Acer pseudoplatanus and Fagus sylvatica seedlings

“…In the present study, this technique was used to compare the hydraulic vulnerability of stem, roots and leaves within intact seedlings, which had an age of only few months, while previous studies dealt with either saplings or detached organs of adult trees (e.g. Choat et al ., , ; Cochard et al ., ; Bouche et al ., ; Cuneo et al ., ; Knipfer et al ., , ; Ryu et al ., ; Nardini et al ., ; Nolf et al ., ; Scoffoni et al ., ). Interestingly, the mean vulnerability of seedling stems was lower than that of branches from adult trees of A. pseudoplatanus (Ψ 50 −1.60 and −2.2 MPa from Tissier et al ., and Lens et al ., ; respectively).…”

Over‐accumulation of abscisic acid in transgenic tomato plants increases the risk of hydraulic failure

“…The transgenic line was found to be 43% and 22% more vulnerable to xylem embolism in stems than the wild type after 90 and 120 days of growth, respectively. This is critical because direct, non‐invasive observations of embolism thresholds in plants subject to dehydration‐rehydration cycles have recently highlighted the lack of xylem embolism recovery under tension (Charrier et al, , in grapevine; Choat et al, , in eucalypts and pin oak; Johnson et al, , in wheat; Knipfer et al, , in laurel). Given that the sp12 transgenic plants showed a similar water potential threshold inducing stomatal closure to the wild type, their greater vulnerability to xylem embolism resulted in a reduced HSM and thereby increased vulnerability to hydraulic failure.…”

Water relations in silver birch during springtime: How is sap pressurised?

“…; Knipfer et al . ). In any case, ‘novel refilling’ (if it exists), root pressure and springtime pressurisation in deciduous trees all lead to embolism refilling and these have been suggested to occur through common mechanisms ( e.g .…”