Ascent of Sap

Dixon, Henry H.; Joly, J. Swift

doi:10.1038/062572a0

Cited by 124 publications

(138 citation statements)

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“…Los eventos de congelamiento-descongelamiento inducen embolismo debido a que el aire no es soluble en el hielo, generándose burbujas durante el congelamiento, las que pueden expandirse durante el descongelamiento, conduciendo a la cavitación (Mayr & Cochard 2003). Los embolismos disminuyen el flujo de agua a través de los conductos xilemáticos (Boehm 1893, Dixon & Joly 1894, Richter 1972, Jackson & Grace 1994, llegando a ser letales en algunos casos (Mayr et al 2014).…”

Section: Introductionunclassified

Conductancia hidráulica foliar y vulnerabilidad a la cavitación disminuyen con la altitud en Phacelia secunda J.F. Gmel. (Boraginaceae)

2015

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High mountain ecosystems are characterized by freezing temperatures. Freeze-thaw events can induce embolism in plant xylem. The risk of embolism increases with the conduit diameter, because wider xylem vessels can contain larger amounts of dissolved gas that after water freeze may form big bubbles producing cavitation. Thus smaller vessels could be advantageous in habitats prone to freezing events. However, smaller conduits decrease hydraulic conductance. The leaf hydraulic conductance (Kf) is a measure of the efficiency in the water transport across the leaf, and it is defined as the ratio between the water flux across the leaf and the difference of hydraulic potential across the leaf. Apparently, Kf is a bottleneck for hydraulic conductance of the whole plant and probably also a crucial factor in gas exchange. In this work we evaluated how the elevational origin of P. secunda can affect the hydraulic conductance of the leaf and the cavitation vulnerability of the vessels. We postulate that plants of P. secunda from higher elevations, as exposed to higher frequency of freezing events, have minor vessels diameter and lower Kf than plants from lower elevations. To test our hypothesis, we determined under field conditions the leaf hydraulic conductance (Kf), in plants from an altitudinal gradient (1,600, 2,800 and 3,600 m) in the Gayana Bot. 72(1): [84][85][86][87][88][89][90][91][92][93] 2015

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Section: Introductionunclassified

Conductancia hidráulica foliar y vulnerabilidad a la cavitación disminuyen con la altitud en Phacelia secunda J.F. Gmel. (Boraginaceae)

2015

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“…It is well structured around two main axes: the cohesion-tension theory [37,38,92] of the ascent of sap which deals with the physics of the sap movement, and the electrical analogy used for modeling water transport within the tree and in the soil-plant water continuum, using resistances, capacitances, water potentials, flow. Presentation of the cohesion-tension theory and its current controversies have been presented in many recent papers [26,33,82,113,135].…”

Section: Introductionmentioning

confidence: 99%

Hydraulic architecture of trees: main concepts and results

2002

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-Since about twenty years, hydraulic architecture (h.a.) is, doubtless, the major trend in the domain of plants (and especially trees) water relations. This review encompasses the main concepts and results concerning the hydraulic of architecture of trees. After a short paragraph about the definition of the h.a., the qualitative and quantitative characteristics of the h.a. are presented. This is an occasion to discuss the pipe model from the h.a. point of view. The second part starts with the central concept of embolism and give a review of important experimental results and questions concerning summer and winter embolism. The last part deals with the coupling between hydraulic and stomatal conductances. It discusses the theoretical and experimental relationships between transpiration and leaf water potential during a progressive soil drought, the increase of soil-root resistance and its consequences in term of xylem vulnerability, the factors controlling the daily maximum transpiration and how stomates can prevent "run away embolism". In conclusion different kinds of unsolved questions of h.a., which can be a matter of future investigations, are presented in addition with a classification of trees behaviour under drought conditions. To end, an appendix recalls the notions of water potential, pressure and tension.hydraulic architecture / cohesion-tension theory / summer embolism / winter embolism / drought resistance Résumé -Architecture hydraulique des arbres : concepts principaux et résultats. Sans aucun doute, depuis une vingtaine d'années, l'architecture hydraulique (a.h.) est devenue une approche majeure dans le domaine des relations plantes-eau (et particulièrement pour les arbres). Cette revue présente les principaux concepts et résultats concernant l'a.h. Après un bref paragraphe sur la définition de l'a.h., les caractéristiques qualitatives et quantitatives définissant l'a.h. sont passées en revue. À cette occasion le « pipe model » est discuté du point de vue de l'a.h. La seconde partie commence avec le concept central d'embolie et continue avec une présentation des principaux résultats et questions touchant l'embolie estivale et l'embolie hivernale. La dernière partie analyse le « couplage » entre les conductances hydraulique et stomatique. Il y est discuté des relations théoriques et expérimentales entre la transpiration et le potentiel hydrique foliaire durant la mise en place d'une sécheresse progressive du sol, de l'augmentation de la résistance sol-racines et de ses conséquences en terme de vulnérabilité du xylème, des facteurs contrôlant la transpiration maximale journalière et de quelle manière les stomates peuvent prévenir l'emballement de l'embolie. La conclusion fait état de différentes questions non résolues, qui pourraient faire l'objet de recherches futures et esquisse une classification du comportement des arbres vis-à-vis de la sécheresse. Pour finir, un appendice rappelle les notions de potentiel hydrique, de pression et de tension.architecture hydraulique / théorie de la cohé...

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“…Water is transported through the xylem under tension and in a metastable state, making it inherently vulnerable to cavitation, the rapid phase change of liquid water to vapor (Dixon and Joly, 1895;Hayward, 1971;Tyree and Sperry, 1989). The resulting gas embolisms block water transport in the affected xylem vessel.…”

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confidence: 99%

In Vivo Visualizations of Drought-Induced Embolism Spread in Vitis vinifera

et al. 2013

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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 nondestructive diagnostic imaging tool, high-resolution x-ray computed tomography, we documented the dynamics of drought-induced embolism in grapevine (Vitis vinifera) plants in vivo, producing the first three-dimensional, highresolution, time-lapse observations of embolism spread. Embolisms formed first in the vessels surrounding the pith at stem water potentials of approximately -1.2 megapascals 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 high-resolution x-ray computed tomography images showed good agreement with previously published nuclear magnetic resonance imaging and hydraulic conductivity experiments also using grapevine. 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.

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Ascent of Sap

Cited by 124 publications

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Conductancia hidráulica foliar y vulnerabilidad a la cavitación disminuyen con la altitud en Phacelia secunda J.F. Gmel. (Boraginaceae)

Conductancia hidráulica foliar y vulnerabilidad a la cavitación disminuyen con la altitud en Phacelia secunda J.F. Gmel. (Boraginaceae)

Hydraulic architecture of trees: main concepts and results

In Vivo Visualizations of Drought-Induced Embolism Spread in Vitis vinifera

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