Xylem water potentials and hydraulic conductances in eight species of ferns

1985 ◽  
Vol 63 (3) ◽  
pp. 632-637 ◽  
Author(s):  
Howard W. Calkin ◽  
Arthur C. Gibson ◽  
Park S. Nobel
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Morphology ◽  
Close Agreement ◽  
Flow Rates ◽  
Xylem Structure ◽  
Physical Constraints ◽  
Intact Plants ◽  
Water Potentials ◽  
Potential Gradients

Water potentials, flow rates, and anatomy of xylary elements were studied in eight species of ferns to assess the physical constraints that xylem structure presents to water flow. Comparisons were made among ferns of different leaf morphology as well as between a fern with vessels and ferns with tracheids only. Hydraulic conductance was measured by forcing a solution through excised plant segments. These hydraulic conductances were in close agreement with conductances calculated from water potential gradients and flows measured in intact plants. In three species, backflushing excised segments by forcing a basipetal flow increased subsequently measured conductances two- to six-fold, indicating that the xylem of these three species was partially blocked in intact plants. Hagen–Poiseuille estimates of conductance based on xylary element diameters were 1.8–2.7 times the conductances measured for excised segments. Hydraulic conductances of tracheids and vessels of ferns thus deviate from those of ideal capillaries of similar diameter to about the same extent as has been reported for tracheids in conifers and for vessels in dicotyledons.

STEADY STATE RESISTANCE TO WATER FLOW IN CORN UNDER WELL WATERED CONDITIONS

1975 ◽  
Vol 55 (4) ◽  
pp. 941-948 ◽  
Author(s):  
P. A. DUBÉ ◽  
K. R. STEVENSON ◽  
G. W. THURTELL ◽  
H. H. NEUMANN
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Leaf Water Potential ◽  
Water Movement ◽  
Leaf Water ◽  
In Vivo Detection ◽  
Staining Techniques ◽  
Total Plant ◽  
Potential Gradients

Determinations of plant resistance to water flow from measurements of leaf water potential at steady transpiration rates were made on different lines of corn (Zea mays L.). Two inbreds, Q188, a wilting mutant, and DR1, an inbred line shown to have at least some heat and drought tolerance under field conditions, were compared to a commercial single-cross hybrid, United 106. The purpose of the experiment was to isolate the cause of the wilting characteristic of Q188. A linear relationship was found between leaf water potential and transpiration rate for all lines. No water potential gradients were found at zero transpiration. Low total plant resistances were observed in United 106 and DR1, with the major resistance being in the root system in both genotypes. Although the resistance to water movement through the roots and lower stalk in Q188 did not appear to differ from those of the other lines, a much larger resistance was found in the upper stalk of Q188; resistance to water movement through the lower stalk (up to node 5) decreased as the plants matured from 55 to 70 days of age but no comparable changes occurred in the upper portions of the stem. In vivo detection of the xylem vessels with staining techniques confirmed the observed differences in resistances.

Impact of soil water potential pattern on root water uptake distribution and leaf water potential

2021 ◽  
Author(s):  
Ali Mehmandoost Kotlar ◽  
Mathieu Javaux
Keyword(s):  
Water Potential ◽  
Root System ◽  
Soil Water ◽  
Water Flow ◽  
Water Uptake ◽  
Leaf Water Potential ◽  
Root Water Uptake ◽  
Leaf Water ◽  
Hydraulic Lift ◽  
Water Potentials

<p>Root water uptake is a major process controlling water balance and accounts for about 60% of global terrestrial evapotranspiration. The root system employs different strategies to better exploit available soil water, however, the regulation of water uptake under the spatiotemporal heterogeneous and uneven distribution of soil water is still a major question. To tackle this question, we need to understand how plants cope with this heterogeneity by adjustment of above ground responses to partial rhizosphere drying. Therefore, we use R-SWMS simulating soil water flow, flow towards the roots, and radial and the axial flow inside the root system to perform numerical experiments on a 9-cell gridded rhizotrone (50 cm×50 cm). The water potentials in each cell can be varied and fixed for the period of simulation and no water flow is allowed between cells while roots can pass over the boundaries. Then a static mature maize root architecture to different extents invaded in all cells is subjected to the various arrangements of cells' soil water potentials. R-SWMS allows determining possible hydraulic lift in drier areas. With these simulations, the variation of root water and leaf water potential will be determined and the role of root length density in each cell and corresponding average soil-root water potential will be statistically discussed.</p>

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.

scholarly journals Evidence for a multicellular symplasmic water pumping mechanism across vascular plant roots

2021 ◽  
Author(s):  
Valentin Couvreur ◽  
Adrien Heymans ◽  
Guillaume Lobet ◽  
Xavier Draye
Keyword(s):  
Water Potential ◽  
Water Flow ◽  
Land Surface ◽  
Vascular Plant ◽  
Plant Water ◽  
Plant Hydraulics ◽  
Water Pumping ◽  
Potential Gradients ◽  
Water Tension ◽  
The Impact

With global warming, climate zones are projected to shift poleward, and the frequency and intensity of droughts to increase, driving threats to crop production and ecosystems. Plant hydraulic traits play major roles in coping with such droughts, and process-based plant hydraulics (water flowing along decreasing pressure or total water potential gradients) has newly been implemented in land surface models. An enigma reported for the past 35 years is the observation of water flowing along increasing water potential gradients across roots. By combining the most advanced modelling tool from the emerging field of plant micro-hydrology with pioneering cell solute mapping data, we found that the current paradigm of water flow across roots of all vascular plants is incomplete: it lacks the impact of solute concentration (and thus negative osmotic potential) gradients across living cells. This gradient acts as a water pump as it reduces water tension without loading solutes in plant vasculature (xylem). Importantly, water tension adjustments in roots may have large impacts in leaves due to the tension-cavitation feedback along stems. Here, we mathematically demonstrate the water pumping mechanism by solving water flow equations analytically on a triple-cell system. Then we show that the simplistic upscaled equations hold in 2- and 3-D maize, grapevine and Arabidopsis complex hydraulic anatomies, and that water may flow uphill of water potential gradients toward xylem as observed experimentally. Besides its contribution to the fundamental understanding of plant water relations, this study lays new foundations for future multidisciplinary research encompassing plant physiology and ecohydrology, and has the ambition to mathematically capture a keystone process for the accurate forecasting of plant water status in crop models and LSMs.

Hydraulic Conductance and Xylem Structure in Tracheid-Bearing Plants

IAWA Journal ◽  
1985 ◽  
Vol 6 (4) ◽  
pp. 293-302 ◽  
Author(s):  
Arthur C. Gibson ◽  
Howard W. Calkin ◽  
Park S. Nobel
Keyword(s):  
Water Flow ◽  
Unit Length ◽  
Hydraulic Conductance ◽  
Distal Portion ◽  
Pteris Vittata ◽  
Root Tips ◽  
Xylem Structure ◽  
Pit Membrane ◽  
Potential Gradients ◽  
Uniform Diameter

To understand water flow in tracheary elements, hydraulic conductances per unit length were measured and then compared with theoretical values calculated from xylem anatomical measurements using the Hagen -Poiseuille relation for nine species of pteridophytes, including Psilotum and eight species of ferns. In ferns the water potential gradients were essentially constant from the root tips to the distal portion of the leaf rachises, although somewhat larger gradients were found from the petiolule onward. Although tracheid number and diameter apparently controlled water flow in xylem, estimates of hydraulic conductance per unit length predicted from tracheid numbers and diameters were generally twice those actually measured from plants under steady-state conditions. A model was developed to account for this discrepancy for Pteris vittata, indicating that pit membrane resistances may contribute 70% of the total resistance to water flow in this fern. This may account for the generally observed deviation of tracheid performance from that predicted for ideal capillaries of uniform diameter.

scholarly journals An Apparatus For Measuring Water Potentials in the Xylem of Intact Plants

1965 ◽  
Vol 18 (3) ◽  
pp. 487 ◽  
Author(s):  
ARG Lang ◽  
HD Barrs
Keyword(s):  
Water Potential ◽  
New Method ◽  
Intact Plants ◽  
Water Potentials ◽  
Pepper Plants

A new method and apparatus for estimating water potentials in the xylem of intact plants are described. The apparatus is based on the thermocouple psychro-meter method of measuring water potentials, but measurements are made on leaves which remain attached to plants. Illustrative experiments are described, in which continuous records of the estimated water potential in the xylem of cotton and pepper plants are given for periods of up to 10 hr.

scholarly journals Geometrical Optimization of a Venturi-Type Microbubble Generator Using CFD Simulation and Experimental Measurements

Designs ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 4
Author(s):  
Dillon Alexander Wilson ◽  
Kul Pun ◽  
Poo Balan Ganesan ◽  
Faik Hamad
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Cfd Simulation ◽  
Air Flow ◽  
Bubble Diameter ◽  
Diameter Ratio ◽  
Experimental Measurements ◽  
Cfd Model ◽  
Flow Rates ◽  
Throat Diameter

Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture and engineering to medical applications. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and computational Fluid Dynamics (CFD) simulation are performed for three water flow rates and three with three different air flow rates. The experimental data presented in the paper are used to validate the CFD model. Then, the CFD model is used to study the effect of diverging angle and throat length/throat diameter ratio on the size of the microbubble produced by the Venturi-type microbubble generator. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubbles. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.

NITROGEN TRANSFORMATIONS NEAR UREA IN SOIL WITH DIFFERENT WATER POTENTIALS

1988 ◽  
Vol 68 (3) ◽  
pp. 569-576 ◽  
Author(s):  
YADVINDER SINGH ◽  
E. G. BEAUCHAMP
Keyword(s):  
Water Potential ◽  
Soil Water ◽  
Incubation Period ◽  
Relative Rate ◽  
Soil Water Potential ◽  
Nitrification Inhibitor ◽  
Silt Loam ◽  
Nitrogen Transformations ◽  
Water Potentials ◽  
Initial Soil

Two laboratory incubation experiments were conducted to determine the effect of initial soil water potential on the transformation of urea in large granules to nitrite and nitrate. In the first experiment two soils varying in initial soil water potentials (− 70 and − 140 kPa) were incubated with 2 g urea granules with and without a nitrification inhibitor (dicyandiamide) at 15 °C for 35 d. Only a trace of [Formula: see text] accumulated in a Brookston clay (pH 6.0) during the transformation of urea in 2 g granules. Accumulation of [Formula: see text] was also small (4–6 μg N g−1) in Conestogo silt loam (pH 7.6). Incorporation of dicyandiamide (DCD) into the urea granule at 50 g kg−1 urea significantly reduced the accumulation of [Formula: see text] in this soil. The relative rate of nitrification in the absence of DCD at −140 kPa water potential was 63.5% of that at −70 kPa (average of two soils). DCD reduced the nitrification of urea in 2 g granules by 85% during the 35-d period. In the second experiment a uniform layer of 2 g urea was placed in the center of 20-cm-long cores of Conestogo silt loam with three initial water potentials (−35, −60 and −120 kPa) and the soil was incubated at 15 °C for 45 d. The rate of urea hydrolysis was lowest at −120 kPa and greatest at −35 kPa. Soil pH in the vicinity of the urea layer increased from 7.6 to 9.1 and [Formula: see text] concentration was greater than 3000 μg g−1 soil. There were no significant differences in pH or [Formula: see text] concentration with the three soil water potential treatments at the 10th day of the incubation period. But, in the latter part of the incubation period, pH and [Formula: see text] concentration decreased with increasing soil water potential due to a higher rate of nitrification. Diffusion of various N species including [Formula: see text] was probably greater with the highest water potential treatment. Only small quantities of [Formula: see text] accumulated during nitrification of urea – N. Nitrification of urea increased with increasing water potential. After 35 d of incubation, 19.3, 15.4 and 8.9% of the applied urea had apparently nitrified at −35, −60 and −120 kPa, respectively. Nitrifier activity was completely inhibited in the 0- to 2-cm zone near the urea layer for 35 days. Nitrifier activity increased from an initial level of 8.5 to 73 μg [Formula: see text] in the 3- to 7-cm zone over the 35-d period. Nitrifier activity also increased with increasing soil water potential. Key words: Urea transformation, nitrification, water potential, large granules, nitrifier activity, [Formula: see text] production

scholarly journals Comparison of Optimization-Regulation Algorithms for Secondary Cooling in Continuous Steel Casting

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 237
Author(s):  
Michal Brezina ◽  
Tomas Mauder ◽  
Lubomir Klimes ◽  
Josef Stetina
Keyword(s):  
Convergence Rate ◽  
Water Flow ◽  
Steel Casting ◽  
Casting Process ◽  
Continuous Steel Casting ◽  
Continuous Steel ◽  
Cooling Zone ◽  
Secondary Cooling ◽  
Flow Rates ◽  
Secondary Cooling Zone

The paper presents the comparison of optimization-regulation algorithms applied to the secondary cooling zone in continuous steel casting where the semi-product withdraws most of its thermal energy. In steel production, requirements towards obtaining defect-free semi-products are increasing day-by-day and the products, which would satisfy requirements of the consumers a few decades ago, are now far below the minimum required quality. To fulfill the quality demands towards minimum occurrence of defects in secondary cooling as possible, some regulation in the casting process is needed. The main concept of this paper is to analyze and compare the most known metaheuristic optimization approaches applied to the continuous steel casting process. Heat transfer and solidification phenomena are solved by using a fast 2.5D slice numerical model. The objective function is set to minimize the surface temperature differences in secondary cooling zones between calculated and targeted surface temperatures by suitable water flow rates through cooling nozzles. Obtained optimization results are discussed and the most suitable algorithm for this type of optimization problem is identified. Temperature deviations and cooling water flow rates in the secondary cooling zone, together with convergence rate and operation times needed to reach the stop criterium for each optimization approach, are analyzed and compared to target casting conditions based on a required temperature distribution of the strand. The paper also contains a brief description of applied heuristic algorithms. Some of the algorithms exhibited faster convergence rate than others, but the optimal solution was reached in every optimization run by only one algorithm.

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.

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