Control of Water Transport in Local Root Regions of Attached and Isolated Roots by Means of the Osmotic Pressure of the External Solution

Rosene, Hilda F.

doi:10.1002/j.1537-2197.1941.tb07987.x

Cited by 35 publications

(4 citation statements)

References 11 publications

(12 reference statements)

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“…Transpiration is a rough measure of water absorption and its reduction by 50% indicates that salinity reduces the transpiration rate. For other plant species, water uptake has been reported to stop at much lower salt concentration levels (Rosene, 1941).…”

Section: Effect Of Naci Concentration On Water Absorptionmentioning

confidence: 99%

Genotypic response to sodium chloride salinity of four major olive cultivars (Olea europea L.)

Therios

Misopolinos

1988

Plant Soil

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The relative tolerance to NaC1 of the olive cultivars 'Amphissis', 'Chondrolia Chalkidikis', 'Koroneiki' and 'Megaritiki' was studied in a nutrient-solution pot experiment. Three-year-old plants produced from cuttings were transplanted to sand-perlite (1/1) culture and irrigated with 1/2 strength Hoagland solution containing NaC1 at various levels, i.e. O, 15, 30, 45, 60 and 80meql -l in the first and 0, 30, 60, 90, 120 and 150meq 1 -I in the second experiment. The overall results indicate that NaCI application had a definite growth-reducing effect under the conditions of the experiment, but to a different extent in each cultivar.

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Section: Effect Of Naci Concentration On Water Absorptionmentioning

confidence: 99%

Genotypic response to sodium chloride salinity of four major olive cultivars (Olea europea L.)

Therios

Misopolinos

1988

Plant Soil

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“…Effects of axial polarity and axial differentiation of roots arose in experiments with excised segments from roots. Exudation from root segments without a root apex and with xylem vessels cut at both ends was demonstrated for onion roots in a saturated atmosphere with several potometers attached along the roots [10,11]. The 25 mm long onion root segments absorbed water from three attached potometers along the axis and then exuded at the basal end (distal to the original apex), while the direction of fluid flow (uptake or efflux) at the apical end depended on the length of removed apical tissue (Figure 4A).…”

Section: Exudation Of Root Segments Without Root Apex and Stem Exudationmentioning

confidence: 99%

A Quest for Mechanisms of Plant Root Exudation Brings New Results and Models, 300 Years after Hales

Volkov

Schwenke

2020

Plants

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The review summarizes some of our current knowledge on the phenomenon of exudation from the cut surface of detached roots with emphasis on results that were mostly established over the last fifty years. The phenomenon is quantitatively documented in the 18th century (by Hales in 1727). By the 19th century, theories mainly ascribed exudation to the secretion of living root cells. The 20th century favored the osmometer model of root exudation. Nevertheless, growing insights into the mechanisms of water transport and new or rediscovered observations stimulated the quest for a more adequate exudation model. The historical overview shows how understanding of exudation changed with time following experimental opportunities and novel ideas from different areas of knowledge. Later theories included cytoskeleton-dependent micro-pulsations of turgor in root cells to explain the observed water exudation. Recent progress in experimental biomedicine led to detailed study of channels and transporters for ion transport via cellular membranes and to the discovery of aquaporins. These universal molecular entities have been incorporated to the more complex models of water transport via plant roots. A new set of ideas and explanations was based on cellular osmoregulation by mechanosensitive ion channels. Thermodynamic calculations predicted the possibility of water transport against osmotic forces based on co-transport of water with ions via cation-chloride cotransporters. Recent observations of rhizodermis exudation, exudation of roots without an external aqueous medium, segments cut from roots, pulses of exudation, a phase shifting of water uptake and exudation, and of effects of physiologically active compounds (like ion channel blockers, metabolic agents, and cytoskeletal agents) will likely refine our understanding of the phenomenon. So far, it seems that more than one mechanism is responsible for root pressure and root exudation, processes which are important for refilling of embolized xylem vessels. However, recent advances in ion and water transport research at the molecular level suggest potential future directions to understanding of root exudation and new models awaiting experimental testing.

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“…There was good evidence that intact and excised roots of corresponding age and length showed similar behavior with respect to absolute rates and axial gradients of water uptake (Rosene, 1941a). Rosene (1941b) determined the driving force for water uptake by applying osmotic solutions to different root zones at concentrations just sufficient to stop the water flow. Taking into account a reflection coefficient of about 0.65 for the solute used (KNO,; our unpublished result), the driving force in the absorption experiment could be calculated to be about 0.4 MPa.…”

Section: Lprmentioning

confidence: 99%

“…However, it is doubtful whether RH really was 100% as stated by Rosene (1941b), so that even at near water saturation, transpiration (pressure)-driven water uptake could have substantially contributed to total water absorption. Therefore, the driving force in the experiments of Rosene (1937) may have been a mixed hydrostatic and osmotic gradient and the absolute value of Lp, would be, thus, understandable.…”

Section: Lprmentioning

confidence: 99%

Water Transport in Onion (Allium cepa L.) Roots (Changes of Axial and Radial Hydraulic Conductivities during Root Development)

Melchior¹,

Steudle²

1993

Plant Physiol.

100

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The hydraulic architecture of developing onion (Allium cepa L. cv Calypso) roots grown hydroponically was determined by measuring axial and radial hydraulic conductivities (equal to inverse of specific hydraulic resistances). In the roots, Casparian bands and suberin lamellae develop in the endodermis and exodermis (equal to hypodermis). Using the root pressure probe, changes of hydraulic conductivities along the developing roots were analyzed with high resolution. Axial hydraulic conductivity (L,) was also calculated from stained cross-sections according to Poiseuille's law.Near the base and the tip of the roots, measured and calculated 1, values were similar. However, at distances between 200 and 300 mm from the apex, measured values of L, were smaller by more than 1 order of magnitude than those calculated, probably because of remaining cross walls between xylem vessel members. During development of root xylem, L. increased by 3 orders of magnitude. In the apical 30 mm (tip region), axial resistance limited water transport, whereas in basal parts radial resistances (low radial hydraulic conductivity, Lp,) controlled the uptake. Because of the high axial hydraulic resistance in the tip region, this zone appeared to be "hydraulically isolated from the rest of the root. Changes of the Lp. of the roots were determined by measuring the hydraulic conductance of roots of different length and referring these data to unit surface area. At distances between 30 and 150 mm from the root tip, Lp, was fairly constant (1.4 X lO-' m s-' MPa-'). In more basal root zones, Lp, was considerably smaller and varied between roots. The low contribution of basal zones t o the overall water uptake indicated an influence of the exodermal Casparian bands and/or suberin lamellae in the endodermis or exodermis, which develop at distances larger than 50 to 60 mm from the root tip.

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Control of Water Transport in Local Root Regions of Attached and Isolated Roots by Means of the Osmotic Pressure of the External Solution

Cited by 35 publications

References 11 publications

Genotypic response to sodium chloride salinity of four major olive cultivars (Olea europea L.)

Genotypic response to sodium chloride salinity of four major olive cultivars (Olea europea L.)

A Quest for Mechanisms of Plant Root Exudation Brings New Results and Models, 300 Years after Hales

Water Transport in Onion (Allium cepa L.) Roots (Changes of Axial and Radial Hydraulic Conductivities during Root Development)

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