The hydraulic architecture of Thuja occidentalis

1983 ◽  
Vol 61 (8) ◽  
pp. 2105-2111 ◽  
Author(s):  
M. T. Tyree ◽  
M. E. D. Graham ◽  
K. E. Cooper ◽  
L. J. Bazos
Keyword(s):  
Water Potential ◽  
Water Flow Rate ◽  
Potential Gradient ◽  
Pressure Potential ◽  
Thuja Occidentalis ◽  
Unit Leaf ◽  
Leaf Surface Area ◽  
Potential Gradients ◽  
Evaporative Flux ◽  
Stem Segments

Leaf specific conductivities (LSC's) were measured on stem segments excised from various points within the canopy of eastern white cedar trees, Thuja occidentalis L. LSC is defined as the water flow rate (kilograms per second) through a stem caused by a unit of pressure potential gradient (megapascals per metre) per unit leaf surface area supplied by the stem (square metres). LSC's were measured on stems of various diameters and were found to vary over a factor of 30 in magnitude from 1 × 10−5 kg s−1 m−1 MPa−1 for stems 1 mm in diameter to 3 × 10−4 kg s−1 m−1 MPa−1 for stems 100 mm in diameter. LSC was found to be related to stem diameter (D (millimetres)) by the following empirical formula: LSC = 9.58 × 10−6 × D0.727. LSC's measured on stem segments including a node had significantly lower LSC's than internodal stem segments of the same length. Various water relations parameters were measured on cedar trees on a diurnal basis including evaporative flux, leaf resistance to evaporation, shoot water potential, air temperature, and air humidity. Water potential isotherms were also measured on excised green shoots. From the above data, we estimate that about 15% of the total water evaporated from green shoots comes from stored water while the shoot water potentials are growing progressively negative. The typical peak evaporative flux in midday was 1.5 × 10−5 kg s−1 m−2; using this value and our measured LSC's we estimate that the pressure potential gradients in the stems must be 50 kPa m−1 in stems 100 mm in diameter and 1500 kPa m−1 in stems 1 mm in diameter. Pressure potential gradients were measured in stems 30 to 50 mm in diameter by the pressure bomb technique and were found to be 69 kPa m−1 during a typical afternoon and this confirms the accuracy of the above estimates.

Accuracy and Usefulness of Psychrometer and Pressure Chamber for Evaluating Water Potentials of Pinus radiata Needles

1982 ◽  
Vol 9 (5) ◽  
pp. 499 ◽  
Author(s):  
BD Millar
Keyword(s):  
Water Potential ◽  
Pinus Radiata ◽  
Xylem Sap ◽  
Pressure Chamber ◽  
Pressure Potential ◽  
Pine Trees ◽  
Average Water ◽  
Potential Gradients ◽  
Fundamental Uncertainty ◽  
The One

Pressure chamber evaluations of xylem sap pressure potential (P) and thermocouple psychrometric evaluations of average water potential (Ψl) in needles from both transpiring and non-transpiring pine trees (Pinus radiata D. Don) were compared in order to determine the relative accuracy and usefulness of these methods for assessing Ψl. Markedly different but linear P v. Ψl relationships were obtained for pine needles of different age and also for the case where resin exudation masked the xylem and led to a 'resin error'. Evidence suggests that these differences are mainly due to injection and resin errors in pressure chamber determinations totalling as much as 1 MPa (a 10 bar). The psychrometric method appears to be the much more accurate. Radial water potential gradients across leaves did not result in differences between evaluations of P and Ψl, at least in P. radiata. The need for multiple 'calibrations' of the pressure chamber and the fundamental uncertainty about the constancy of such calibrations on the one hand and the slowness of the excised-needle psychrometer on the other can restrict the usefulness of these methods.

Water relations and xylem anatomy of ferns

1985 ◽  
Vol 86 ◽  
pp. 81-92 ◽  
Author(s):  
A. C. Gibson ◽  
H. W. Calkin ◽  
D. O. Raphael ◽  
P. S. Nobel
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Water Relations ◽  
Unit Length ◽  
Potential Gradient ◽  
Hydraulic Conductance ◽  
Xylem Anatomy ◽  
Potential Gradients ◽  
Water Potential Gradient ◽  
Poiseuille Equation

SynopsisThe entire soil-plant-atmosphere continuum must be analysed to elucidate how xylem anatomy relates to water flow in plants. Measurements of water potential gradients and volume of water flow per unit time are needed to obtain values of hydraulic conductance per unit length. By comparing values of hydraulic conductance per unit length along the plant, the regions where xylem structure restricts water flow can be determined. Previous studies of fern water relations demonstrated that very large water potential gradients occurring in stipes of certain ferns were closely correlated with reduced conducting area of stipe xylem. A new study on Cyrtomium falcatum showed that the water potential gradient was relatively small and constant along the stipe and rachis; however, a much larger gradient occurred from the rachies into the pinnae. Hydraulic conductance per unit length varied with the leaf area to be supplied, leading to the fairly constant water potential gradient along the rachis.. The measured hydraulic conductance per unit length was only half the value predicted from the Hagen-Poiseuille equation. Although the Hagen-Poiseuille equation overestimated the measured value by a factor of 2, it did support the assumption that conduit number and lumen diameter are the principal determinants of water conductance in the xylem.

Measuring surface potential components necessary for transmembrane current computation using microfabricated arrays

2005 ◽  
Vol 289 (6) ◽  
pp. H2468-H2477 ◽  
Author(s):  
J. James Wiley ◽  
Raymond E. Ideker ◽  
William M. Smith ◽  
Andrew E. Pollard
Keyword(s):  
Spatial Resolution ◽  
Current Density ◽  
Potential Gradient ◽  
Electrode Spacing ◽  
Back Side ◽  
Transmembrane Current ◽  
Fine Wire ◽  
Microfabricated Arrays ◽  
Potential Gradients ◽  
Unipolar Electrograms

This study was designed to test the feasibility of using microfabricated electrodes to record surface potentials with sufficiently fine spatial resolution to measure the potential gradients necessary for improved computation of transmembrane current density. To assess that feasibility, we recorded unipolar electrograms from perfused rabbit right ventricular free wall epicardium ( n = 6) using electrode arrays that included 25-μm sensors fabricated onto a flexible substrate with 75-μm interelectrode spacing. Electrode spacing was therefore on the size scale of an individual myocyte. Signal conditioning adjacent to the sensors to control lead noise was achieved by routing traces from the electrodes to the back side of the substrate where buffer amplifiers were located. For comparison, recordings were also made using arrays built from chloridized silver wire electrodes of either 50-μm (fine wire) or 250-μm (coarse wire) diameters. Electrode separations were necessarily wider than with microfabricated arrays. Comparable signal-to-noise ratios (SNRs) of 21.2 ± 2.2, 32.5 ± 4.1, and 22.9 ± 0.7 for electrograms recorded using microfabricated sensors ( n = 78), fine wires ( n = 78), and coarse wires ( n = 78), respectively, were found. High SNRs were maintained in bipolar electrograms assembled using spatial combinations of the unipolar electrograms necessary for the potential gradient measurements and in second-difference electrograms assembled using spatial combinations of the bipolar electrograms necessary for surface Laplacian (SL) measurements. Simulations incorporating a bidomain representation of tissue structure and a two-dimensional network of guinea pig myocytes prescribed following the Luo and Rudy dynamic membrane equations were completed using 12.5-μm spatial resolution to assess contributions of electrode spacing to the potential gradient and SL measurements. In those simulations, increases in electrode separation from 12.5 to 75.0, 237.5, and 875.0 μm, which were separations comparable to the finest available with our microfabricated, fine wire, and coarse wire arrays, led to 10%, 42%, and 81% reductions in maximum potential gradients and 33%, 76%, and 96% reductions in peak-to-peak SLs. Maintenance of comparable SNRs for source electrograms was therefore important because microfabrication provides a highly attractive methods to achieve spatial resolutions necessary for improved computation of transmembrane current density.

scholarly journals Root uptake under mismatched distributions of water and nutrients in the root zone

2020 ◽  
Author(s):  
Jing Yan ◽  
Nathaniel A. Bogie ◽  
Teamrat Ghezzehei
Keyword(s):  
Water Potential ◽  
Nutrient Availability ◽  
Nutrient Management ◽  
Root Zone ◽  
Soil Water Potential ◽  
Potential Gradient ◽  
Hydraulic Redistribution ◽  
Natural Environments ◽  
Water Release ◽  
Dry Soil

Abstract. Most plants derive their water and nutrient needs from soils, where the resources are often scarce, patchy, and ephemeral. In natural environments, it is not uncommon for plant roots to encounter mismatched patches of water-rich and nutrient-rich regions. Such an uneven distribution of resources necessitates plants to rely on strategies that allow them to explore and acquire nutrients from relatively dry patches. We conducted a laboratory study to provide a mechanistic understanding of the biophysical factors that enable this adaptation. We grew plants in split-root pots that permitted precisely controlled spatial distributions of resources. The results demonstrated that spatial mismatch of water and nutrient availability does not cost plant productivity compared to matched distributions. Specifically, we showed that nutrient uptake is not reduced by overall soil dryness, provided that the whole plant has access to sufficient water elsewhere in the root zone. Essential strategies include extensive root proliferation towards nutrient-rich dry soil patches that allows rapid nutrient capture from brief pulses. Using high-frequency water potential measurements, we also observed nocturnal water release by roots that inhabit dry and nutrient-rich soil patches. Soil water potential gradient is the primary driver of this transfer of water from wet to dry soil parts of the root zone, which is commonly known as hydraulic redistribution (HR). The occurrence of HR prevents the soil drying from approaching the permanent wilting point, and thus supports root functions and enhance nutrient availability. Our results indicate that roots facilitate HR by increasing root-hair density and length and deposition of organic coatings that alter water retention. Therefore, we conclude that biologically-controlled root adaptation involves multiple strategies that compensate for nutrient acquisition under mismatched resource distributions. Based on our findings, we proposed a nature-inspired nutrient management strategy for significantly curtailing water pollution from intensive agricultural systems.

Effect of Interspecific Interference, Light Intensity, and Soil Moisture on Soybean (Glycine max), Common Cocklebur (Xanthium strumarium), and Sicklepod (Cassia obtusifolia) Water Uptake

Weed Science ◽  
1993 ◽  
Vol 41 (4) ◽  
pp. 534-540 ◽  
Author(s):  
Ronald E. Jones ◽  
Robert H. Walker
Keyword(s):  
Soil Moisture ◽  
Light Intensity ◽  
Leaf Area ◽  
Water Uptake ◽  
Root Weight ◽  
Pressure Potential ◽  
Unit Leaf Area ◽  
Unit Leaf ◽  
Shoot Weight ◽  
The Relationship

Greenhouse and growth chamber experiments with potted plants were conducted to determine the effects of interspecific root and canopy interference, light intensity, and soil moisture on water uptake and biomass of soybean, common cocklebur, and sicklepod. Canopy interference and canopy plus root interference of soybean with common cocklebur increased soybean water uptake per plant and per unit leaf area. Root interference with soybean decreased common cocklebur water uptake per plant. Canopy interference of soybean with sicklepod increased soybean water uptake per unit leaf area, while root interference decreased uptake per plant. Combined root and canopy interference with soybean decreased water uptake per plant for sicklepod. Soybean leaf area and shoot weight were reduced by root interference with both weeds. Common cocklebur and sicklepod leaf area and shoot weight were reduced by root and canopy interference with soybeans. Only common cocklebur root weight decreased when canopies interfered and roots did not. The relationship between light intensity and water uptake per unit leaf area was linear in both years with water uptake proportional to light intensity. In 1991 water uptake response to tight was greater for common cocklebur than for sicklepod. The relationship between soil moisture level and water uptake was logarithmic. Common cocklebur water uptake was two times that of soybean or sicklepod at −2 kPa of pressure potential. In 1991 common cocklebur water uptake decreased at a greater rate than soybean or sicklepod in response to pressure potential changes from −2 to −100 kPa.

scholarly journals Growth Dynamics and Water Potential Components of Three Summer Squash (Cucurbita pepo L.) Cultivars

2015 ◽  
Vol 43 (2) ◽  
pp. 420-425 ◽  
Author(s):  
Alejo RODRÍGUEZ-BURGOS ◽  
Armando CARRILLO-LÓPEZ ◽  
Tomás OSUNA-ENCISO ◽  
Manuel BÁEZ-SAÑUDO ◽  
Adriana SAÑUDO-BARAJAS ◽  
...  
Keyword(s):  
Water Potential ◽  
Histological Analysis ◽  
Growth Dynamics ◽  
Titratable Acidity ◽  
Soluble Solids ◽  
Pressure Potential ◽  
Horticultural Crop ◽  
Total Soluble Solids ◽  
Summer Squash ◽  
Postharvest Life

Summer squash fruit is a horticultural crop that possesses a very short postharvest life due to its high rates of metabolism and transpirationalong with a low cuticle resistance exhibited mainly when the fruit is harvested at horticultural maturity. This research was realized following thefruit growth of the summer squash cultivars: ‘Enterprise’, ‘Pascola’ and ‘Hurakan F1’, whose seeds were germinated in polystyrene trays and theirseedlings were subsequently transferred to pots for optimum growth under greenhouse conditions. Fruits were sampled at 3, 5, 7 and 9 days afteranthesis (DAA). Physical (weight, diameter, and length of fruit), chemical (pH, titratable acidity and total soluble solids), hydric status (water,osmotic and pressure potentials), and histological analysis were done. The highest number of fruits having marketing quality were shown in both‘Pascola’ and ‘Hurakan F1’ cultivars at 7 DAA, whereas, in ‘Enterprise’ was shown at 9 DAA. Marketing quality fruits from the three cultivarsshowed similarities on pH (about 6.6), titratable acidity (TA) decreases in ‘Enterprise’ and ‘Hurakan F1’, whereas total soluble solids (TSS)decreases in ‘Pascola’ and ‘Hurakan F1’ (pJ 0.5). From 3 to 9 DAA, in all cultivars, the water potential was close to -1.0 MPa, the osmoticpotential showed an increasing pattern ranging between -1.59 and -1.15 MPa, and the pressure potential remained in the positive range. Tissuewater stability was histologically related to a well-defined parenchyma tissue showing thin-walled, polygonal, intact and turgid cells during fruitgrowth.

Comparative analysis reveals gravity is involved in the MIZ1-regulated root hydrotropism

2020 ◽  
Vol 71 (22) ◽  
pp. 7316-7330
Author(s):  
Ying Li ◽  
Wei Yuan ◽  
Luocheng Li ◽  
Hui Dai ◽  
Xiaolin Dang ◽  
...  
Keyword(s):  
Water Potential ◽  
Double Mutant ◽  
Root Elongation ◽  
Vertical Orientation ◽  
Tomato Plants ◽  
Oblique Orientation ◽  
Experimental Systems ◽  
Potential Gradients ◽  
Insight Into

Abstract Hydrotropism is the directed growth of roots toward the water found in the soil. However, mechanisms governing interactions between hydrotropism and gravitropism remain largely unclear. In this study, we found that an air system and an agar–sorbitol system induced only oblique water-potential gradients; an agar–glycerol system induced only vertical water-potential gradients; and a sand system established both oblique and vertical water-potential gradients. We employed obliquely oriented and vertically oriented experimental systems to study hydrotropism in Arabidopsis and tomato plants. Comparative analyses using different hydrotropic systems showed that gravity hindered the ability of roots to search for obliquely oriented water, whilst facilitating roots’ search for vertically oriented water. We found that the gravitropism-deficient mutant aux1 showed enhanced hydrotropism in the oblique orientation but impaired root elongation towards water in the vertical orientation. The miz1 mutant exhibited deficient hydrotropism in the oblique orientation but normal root elongation towards water in the vertical orientation. Importantly, in contrast to miz1, the miz1/aux1 double mutant exhibited hydrotropic bending in the oblique orientation and attenuated root elongation towards water in the vertical orientation. Our results suggest that gravitropism is required for MIZ1-regulated root hydrotropism in both the oblique orientation and the vertical orientation, providing further insight into the role of gravity in root hydrotropism.

scholarly journals Molecular mechanisms mediating root hydrotropism: what we have observed since the rediscovery of hydrotropism

2019 ◽  
Vol 133 (1) ◽  
pp. 3-14
Author(s):  
Yutaka Miyazawa ◽  
Hideyuki Takahashi
Keyword(s):  
Arabidopsis Thaliana ◽  
Water Potential ◽  
Water Availability ◽  
Molecular Mechanisms ◽  
Current Knowledge ◽  
Potential Gradient ◽  
Regulatory Mechanisms ◽  
Directional Growth ◽  
Plant Adaptation ◽  
Water Potential Gradient

AbstractRoots display directional growth toward moisture in response to a water potential gradient. Root hydrotropism is thought to facilitate plant adaptation to continuously changing water availability. Hydrotropism has not been as extensively studied as gravitropism. However, comparisons of hydrotropic and gravitropic responses identified mechanisms that are unique to hydrotropism. Regulatory mechanisms underlying the hydrotropic response appear to differ among different species. We recently performed molecular and genetic analyses of root hydrotropism in Arabidopsis thaliana. In this review, we summarize the current knowledge of specific mechanisms mediating root hydrotropism in several plant species.

A New Explanation for the Osmotic Activity and Ionic Composition of Gastric Juice

1957 ◽  
Vol 192 (1) ◽  
pp. 14-22 ◽  
Author(s):  
Warren S. Rehm ◽  
Warren H. Dennis ◽  
William A. Brodsky
Keyword(s):  
Osmotic Pressure ◽  
Gastric Juice ◽  
Chemical Potential ◽  
Ionic Composition ◽  
Potential Gradient ◽  
Inorganic Ions ◽  
Parietal Cells ◽  
Inorganic Ion ◽  
Potential Gradients ◽  
Osmotic Activity

In an attempt to extend a previously proposed theory of gastric HCl production, the possibility is considered that the surface epithelial cells secrete H+ ions and the parietal cells Cl– ions and water. It is postulated that water is transported as a result of its chemical potential gradient between the interstitial fluid and the canalicular lumen of the parietal cells. It is shown that this scheme can quantitatively explain, without further postulates, the high normalities of secretion found in the glycine experiments of Teorell. However, the scheme predicts for pure gastric juice a higher osmotic pressure than that found. Furthermore, the scheme does not offer an explanation for the presence of the other inorganic ions of gastric juice. In an attempt to account for the observed osmotic pressure and the inorganic ion content of gastric juice, the implications are developed of the assumption that the Na+ ions, K+ ions and some of the secreted Cl– ions are transported across the mucosa in the direction of their electrochemical potential gradients. It is shown that the resulting scheme can account for the composition and osmotic pressure of gastric juice at least as well as any of the schemes proposed by other workers. The implications of the present scheme with respect to the problem of the production of hypertonic and hypotonic secretions are discussed.

Sign in / Sign up

Export Citation Format

Share Document