The kinetics of rehydration of detached sunflower leaves from different initial water deficits

Tyree, Melvin T.; Cruiziat, P.; Benis, M.; LoGULLO, M. A.; Salleo, Sebastiano

doi:10.1111/1365-3040.ep11604553

Cited by 30 publications

(12 citation statements)

References 14 publications

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“…When an estimate of root fresh volume is derived from their dry mass, it is apparent that the total amount of water moved in the transient phase could be easily accounted for by changes in living tissue capacitance in our experiment. Nevertheless, we think that this was not the case: the kinetics of capacitive exchange are always considerably slower and the time constant greatly increases with tissue length and longitudinal resistance (Stroshine et al 1985;Tyree et al 1981). Similar results have been obtained by the cell pressureclamp technique.…”

Section: Discussionsupporting

confidence: 70%

Measurement of apoplasmic and cell-to-cell components of root hydraulic conductance by a pressure-clamp technique

Magnani

Centritto²,

Grace

1996

Planta

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Abstract.A pressure-clamp technique was devised for the direct measurement of cell-to-cell and apoplasmic components of root hydraulic conductance; the experimental results were analyzed in terms of a theoretical model of water and solute flow, based on a composite membrane model of the root. When water is forced under a constant pressure into a cut root system, an exponential decay of flow is observed, until a constant value is attained; when pressure is released, a reverse water flow out of the root system is observed which shows a similar exponential behavour. The model assumes that the transient flow occurs through a cell-to-cell pathway and the observed decrease is the result of accumulation of solutes in front of the root semi-permeable membrane, whilst the steadystate component results from the movement of water through the parallel apoplasmic pathway. Root conductance components are estimated by fitting the model to experimental data. The technique was applied to the root systems of potted cherry (Prunus avium L.) seedlings; average apoplasmic conductance was 15.5 x 10 -9 m 3. s -1' MPa -t, with values ranging from 12.0• 10 -9 to 18.5 x 10-9 m3.s-l-MPa-1; average cell-to-cell conductance was 11.7x 10 -9m3.s -~.MPa -~, with values ranging from 8.5 x 10 .9 to 15.3 x 10 -9 m3.s-l.MPa -1. Cell-to-cell conductance amounted on average to 43% of total root conductance, with values between 41 and 45%. Leaf specific conductance (conductance per unit of leaf area supported) of the root systems ranged from 2.7x10 -s to 5.6xl0-Sm's-l'MPa -t, with an average of 3.7 x 10 -8 m.s-l.MPa -~. The newly developed Abbreviations and symbols: A L 0 = root hydraulic conductance; AaL~ = root apoplasmic conductance; ACCL~, C = root cell-to-cell conductance; C~(t) = concentration of solutes in apical root compartment at time t; Jv = flow of water through the root; ja = apoplasmic flow of water; Jv ~c = cell-to-cell flow of water; LSC = leaf specific conductance of the root system; P = root hydrostatic pressure; P,ppt = applied pressure; n~(t) = root osmotic pressure at time t; rim, osmotic pressure of rooting medium; cr = reflection coefficient of root membrane; z = time constant of cell-to-cell flow decay Correspondence to: F. Magnani; Fax: 44 (31) 662 0478; Tel.: 44 (31) 650 5437; E-mail: fmagnani@srv0.bio.ed.ac.uk technique allows the interaction of mass flow of water and of solutes to be explored in the roots of soil-grown plants.

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Section: Discussionsupporting

confidence: 70%

Measurement of apoplasmic and cell-to-cell components of root hydraulic conductance by a pressure-clamp technique

Magnani

Centritto²,

Grace

1996

Planta

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“…The most detailed study so far (Tyree et al, 1981) was not able to reach a firm conclusion. Things are simpler in a larger leaf with greater volumes of homogeneous tissue like Agave, where Smith & Nobel (1986) were able to decide in favour of a cell to cell path.…”

Section: Historical -Explorations Of Water Paths In Leavesmentioning

confidence: 89%

“…The developments have been ably reviewed by Boyer (1985), himself responsible for emphasising the complications arising from nonreversible entrapment of water in tissues that are growing. The models have become greatly elaborated 1981, Molz & Ferrier, 1982, but the following considerable simplification has been distilled out of the complexities.…”

Section: Historical -Explorations Of Water Paths In Leavesmentioning

confidence: 99%

Tansley Review No. 22 What becomes of the transpiration stream?

1990

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SUMMARY Changes of view on the course of the transpiration stream beyond the veins in leaves are followed from the imbibition theory of Sachs, through the (symplastic) endosmotic theory of Pfeffer (which prevailed almost unquestioned until the late 1930s), to Strugger's experiments with fluorescent dye tracers and the epifluorescence microscope. This latter work persuaded many to return to the apoplastic‐(wall)‐path viewpoint, which, despite early and late criticisms that were never rebutted, is still widely held. Tracer experiments of the same kind are still frequently published without consideration of the evidence that they do not reveal the paths of water movement. Experiments on rehydration kinetics of leaves have not produced unequivocal evidence for either path. The detailed destinies of the solutes that reach the leaf in the transpiration stream have received little attention. Consideration of physical principles governing flow and evaporation in a transpiring leaf emphasizes that: (1) Diffusion over interveinal distances at the rates in water will account for substantial solute movement in a few minutes, even in the absence of flow. (2) Diffusion can occur also against opposing now. (3) Volume fluxes in veins are determined by the diameter of the largest leaves examined contain high conductance supply veins which are tapped into by low‐conductance distributing veins. (4) Edges and teeth of leaves will be places of especially rapid evaporation, and they often have high‐conductance veins leading to them. (5) Solutes in the stream will tend to accumulate at leaf margins. On the basis of recent work, the view is maintained that the water of the stream enters the symplast through cell membranes very close to tracheary elements. Also, that this occurs locally over a small area of membrane. Many solutes in the stream are left outside in the apoplast. This produces regions of high solute concentration in the apoplast and an enrichment of solutes in the stream as it perfuses the leaf. Solutes that enter the symplast are not so easily tracked. Suggestions about where some of them may go can be gained from a fluorescent probe that identifies particular cells (scavenging cells) as having H+‐ATPase porter systems to scrub selected solutes from the stream. Unpublished case‐histories are presented which illustrate many aspects of these processes and principles. These are: (1) Maize leaf veins, where the symplastic water path starts at the parenchyma sheath; (2) Lupin veins, where the symplastic path starts at the bundle sheath and where solutes are concentrated in blind terminations; (3) The edges of maize leaves where flow is enhanced by a large vein (open to the apoplast), and solutes are deposited in the apoplast by evaporation; (4) Poplar leaf teeth, which receive strong flows, and where the epithem cells are scavenging cells; (5) Mimosa leaf marginal hairs, which have scavenging cells at their base; (6) Active hydathodes, whose epithem cells are scavenging cells; (7) Pine needle transfusion tissue, which is a site...

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“…Apoplastic tracer studies (Canny, 1986) and the discovery of aquaporins (Agre et al, 1993;Chrispeels and Agre 1994) have promoted the view in recent years that transmembrane flow may dominate outside-xylem transport (Tyree et al, 1981(Tyree et al, , 1999Sack and Tyree, 2005), at least in the light, when aquaporins may be activated (Cochard et al, 2007). However, a theoretical study by Buckley (2015) that used membrane permeability values from published studies carried out on illuminated leaves concluded that apoplastic transport should dominate.…”

Section: Does Liquid Flow Outside the Xylem Follow Apoplastic And/or mentioning

confidence: 99%

How Does Leaf Anatomy Influence Water Transport outside the Xylem?

et al. 2015

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Leaves are arguably the most complex and important physicobiological systems in the ecosphere. Yet, water transport outside the leaf xylem remains poorly understood, despite its impacts on stomatal function and photosynthesis. We applied anatomical measurements from 14 diverse species to a novel model of water flow in an areole (the smallest region bounded by minor veins) to predict the impact of anatomical variation across species on outside-xylem hydraulic conductance (K ox ). Several predictions verified previous correlational studies: (1) vein length per unit area is the strongest anatomical determinant of K ox , due to effects on hydraulic pathlength and bundle sheath (BS) surface area; (2) palisade mesophyll remains well hydrated in hypostomatous species, which may benefit photosynthesis, (3) BS extensions enhance K ox ; and (4) the upper and lower epidermis are hydraulically sequestered from one another despite their proximity. Our findings also provided novel insights: (5) the BS contributes a minority of outside-xylem resistance; (6) vapor transport contributes up to two-thirds of K ox ; (7) K ox is strongly enhanced by the proximity of veins to lower epidermis; and (8) K ox is strongly influenced by spongy mesophyll anatomy, decreasing with protoplast size and increasing with airspace fraction and cell wall thickness. Correlations between anatomy and K ox across species sometimes diverged from predicted causal effects, demonstrating the need for integrative models to resolve causation. For example, (9) K ox was enhanced far more in heterobaric species than predicted by their having BS extensions. Our approach provides detailed insights into the role of anatomical variation in leaf function.

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The kinetics of rehydration of detached sunflower leaves from different initial water deficits

Cited by 30 publications

References 14 publications

Measurement of apoplasmic and cell-to-cell components of root hydraulic conductance by a pressure-clamp technique

Measurement of apoplasmic and cell-to-cell components of root hydraulic conductance by a pressure-clamp technique

Tansley Review No. 22 What becomes of the transpiration stream?

How Does Leaf Anatomy Influence Water Transport outside the Xylem?

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