Oscillations in Apparent Hydraulic Conductance of Cotton Plants

1985 ◽  
Vol 12 (5) ◽  
pp. 455 ◽  
Author(s):  
J.B Passioura ◽  
C.B Tanner
Keyword(s):  
Pressure Drop ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Pressure Chamber ◽  
Pressure Regulator ◽  
Pneumatic Pressure ◽  
Automatic Pressure ◽  
Cotton Plants ◽  
Damped Oscillation

Cotton plants were grown in pots that could be encased in a pressure chamber so that a pneumatic pressure could be applied to the roots while the shoot was enclosed in an unpressurized cuvette. Enough pressure (the 'balancing pressure') was applied to the roots to raise the pressure of the xylem sap in the shoot to that of the atmosphere, so that a cut in the xylem of the shoot was on the verge of bleeding. The balancing pressure was accurately maintained, despite any changes in the transpirational flux, by means of an automatic pressure regulator. When the transpirational flux was suddenly changed by changing the humidity in the cuvette, the balancing pressure started to oscillate even though flux was steady at its new level, i.e. the apparent hydraulic conductance (the ratio of transpirational flux to the pressure drop across the plant) oscillated. In plants that were phosphorus-deficient, the oscillations were large and had a period of 30-50 min; though damped, they persisted for several cycles. Phosphorussufficient plants gave one, critically-damped, oscillation.

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.

An Automatic Pressure Regulator.

1924 ◽  
Vol 16 (2) ◽  
pp. 160-161 ◽  
Author(s):  
Louis E. Dawson
Keyword(s):  
Pressure Regulator ◽  
Automatic Pressure

scholarly journals Testing for ion-mediated enhancement of the hydraulic conductance of the leaf xylem in diverse angiosperms

2017 ◽  
Vol 4 ◽  
pp. e004 ◽  
Author(s):  
Christine Scoffoni ◽  
Grace John ◽  
Herve Cochard ◽  
Lawren Sack
Keyword(s):  
Water Solution ◽  
Pure Water ◽  
Xylem Sap ◽  
Hydraulic Conductance ◽  
Membrane Pores ◽  
Whole Plant ◽  
Pit Membrane ◽  
Major Bottleneck ◽  
The Difference ◽  
Xylem Conduits

Replacing ultra-pure water solution with ion solution closer to the composition of natural xylem sap increases stem hydraulic conductance by up to 58%, likely due to changes in electroviscosity in the pit membrane pores. This effect has been proposed to contribute to the control of plant hydraulic and stomatal conductance and potentially to influence on carbon balance during dehydration. However, this effect has never been directly tested for leaf xylem, which constitutes a major bottleneck in the whole plant. We tested for an ion-mediated increase in the hydraulic conductance of the leaf xylem (Kx) for seven species diverse in phylogeny and drought tolerance. Across species, no significant changes in Kx were observed between 0 and 15 mM KCl. We further tested for an effect of ion solution during measurements of Kx vulnerability to dehydration in Quercus agrifolia and found no significant impact. These results for leaf xylem contrast with the often strong ion effect reported for stems, and we suggest several hypotheses to account for the difference, relating to the structure of xylem conduits across vein orders, and the ultrastructure of leaf xylem pores. A negligible ion response in leaves would weaken xylem sap ion-mediated control of plant hydraulic conductance, facilitating modeling of whole plant hydraulic behavior and its influence on productivity.

Abscisic Acid Levels in Nacl-Treated Barley, Cotton and Saltbush

1991 ◽  
Vol 18 (1) ◽  
pp. 17 ◽  
Author(s):  
Z Kefu ◽  
R Munns ◽  
RW King
Keyword(s):  
Abscisic Acid ◽  
Water Deficit ◽  
Water Status ◽  
Xylem Sap ◽  
Leaf Water ◽  
Leaf Water Status ◽  
Cotton Plants ◽  
Presence And Absence ◽  
Leaf Water Deficit

Exposing barley and cotton plants to 75 mol m-3 NaCl reduced transpiration and increased abscisic acid (ABA) levels in leaves, roots and xylem sap. Exposing saltbush (Atriplex spongiosa) plants to 75 mol m-3 NaCI, at which concentration they grow best, did not affect transpiration or ABA levels but when the NaCl was increased to 150 mol m-3 transpiration fell and ABA levels rose. ABA levels in leaves were high in salt-treated barley and saltbush even when the leaf water status was raised by pressurising the roots. These responses indicate that an increased leaf ABA level was not triggered by leaf water deficit, but by the root's response to the salinity. The flux of ABA in the xylem sap of the three species was more than enough to account for the amount of ABA in leaves, in the presence and absence of salinity. This suggests that the roots may be the source of at least part of the ABA found in leaves.

scholarly journals Nitrate Transport Rate in the Xylem of Tomato Plants Grafted onto a Vigorous Rootstock

Agronomy ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 182 ◽  
Author(s):  
Francisco Albornoz ◽  
Alonso G. Pérez-Donoso ◽  
Jorge Leigh Urbina ◽  
Matías Monasterio ◽  
Miguel Gómez ◽  
...  
Keyword(s):  
Water Uptake ◽  
N Uptake ◽  
Xylem Sap ◽  
Light Level ◽  
Hydraulic Conductance ◽  
Transport Rate ◽  
Nitrate Transport ◽  
Limited Information ◽  
Cross Sectional ◽  
Tomato Plants

Vigorous interspecific rootstocks increase nitrogen (N) uptake in tomato plants but limited information is available on xylem transport rate. Non-grafted and self-grafted tomato plants cv. Attiya and plants grafted onto an interspecific hybrid, Kaiser, were grown under growth chamber conditions and subjected to two light levels, 400 or 800 µmol PAR m−2 s−1. Plant water uptake, xylem sap NO3− content, and stem hydraulic conductance (ks) were measured after two weeks of growth. Xylem vessel number and diameter were evaluated in cross-sectional stem cuts and the theoretical xylem hydraulic conductance (kh) was calculated. Only the light level modified the xylem NO3− content. Grafting reduced ks by 84% in comparison to non-grafted plants. The water uptake rate and xylem sap NO3− content were 4.02 ± 0.66 g H2O kg−1 DW h−1 and 12.78 ± 1.16 mM, respectively, across all grafting treatments. The rootstock has a higher kh because the vessel diameter is 79.3 ± 14.4 µm while in non-grafted plants it is 62.0 ± 10.1 µm. Nitrate concentration and transport rate changes accordingly to the plant’s growth rate. The vigorous rootstock relies on larger vessels to supply the required amounts of N.

Study on the Characteristics of a New Type Pneumatic Pressure Regulator

2013 ◽  
Vol 347-350 ◽  
pp. 157-161
Author(s):  
Jun Gong Ma ◽  
Xin Hua Chen
Keyword(s):  
Mechanical Valve ◽  
Pressure Control ◽  
Superior Performance ◽  
Mechanical Pressure ◽  
Pressure Regulator ◽  
Valve Body ◽  
Pneumatic Pressure ◽  
Output Pressure ◽  
Flow Disturbances ◽  
Downstream Flow

ressure regulators are very important elements in pneumatic systems. Purely mechanical pressure regulators are commonly used to control the supply pressure to the desired value. The intelligent pneumatic pressure regulator (IPPR) is designed as the demands of pressure control precision increase. Its prominent advantage is the ability to achieve accurate output pressure, remote control and centralized management. In this paper, the IPPR consists of a mechanical valve body, a stepping motor, a microcontroller, a pressure sensor. Herein, its pneumatic characteristics were analyzed, and the pressure control algorithm was presented. The superior performance of IPPR was shown in AMEsim simulation, especially in terms of avoiding affects from upstream pressure and downstream flow disturbances.

Effects of NaCl addition to the growing medium on plant hydraulics and water relations of tomato

2013 ◽  
Vol 40 (5) ◽  
pp. 459 ◽  
Author(s):  
Patrizia Trifilò ◽  
Maria Assunta Lo Gullo ◽  
Fabio Raimondo ◽  
Sebastiano Salleo ◽  
Andrea Nardini
Keyword(s):  
Xylem Sap ◽  
Hydraulic Conductance ◽  
In Planta ◽  
Plant Hydraulics ◽  
Solanum Lycopersicum L ◽  
Growing Medium ◽  
Moderate Salinity ◽  
Salinity Levels ◽  
Half Strength

This work reports on experimental evidence for the role of ion-mediated changes of xylem hydraulic conductivity in the functional response of Solanum lycopersicum L. cv. Naomi to moderate salinity levels. Measurements were performed in fully developed 12-week-old plants grown in half-strength Hoagland solution (control, C-plants) or in the same solution added with 35 mM NaCl (NaCl-plants). NaCl-plants produced a significantly less but heavier leaves and fruits but had similar gas-exchange rates as control plants. Moreover, NaCl-plants showed higher vessel multiple fraction (FVM) than control plants. Xylem sap potassium and sodium concentrations were significantly higher in NaCl-plants than in control plants. When stems were perfused with 10 mM NaCl or KCl, the hydraulic conductance of NaCl plants was nearly 1.5 times higher than in control plants. Accordingly, stem hydraulic conductance measured in planta was higher in NaCl- than in control plants. Our data suggest that tomato plants grown under moderate salinity upregulate xylem sap [Na+] and [K+], as well as sensitivity of xylem hydraulics to sap ionic content, thus, increasing water transport capacity.

Water transfer in a mature oak stand (Quercuspetraea): seasonal evolution and effects of a severe drought

1993 ◽  
Vol 23 (6) ◽  
pp. 1136-1143 ◽  
Author(s):  
N. Bréda ◽  
H. Cochard ◽  
E. Dreyer ◽  
A. Granier
Keyword(s):  
Stomatal Conductance ◽  
Potential Evapotranspiration ◽  
Stomatal Closure ◽  
Time Lag ◽  
Xylem Sap ◽  
Water Shortage ◽  
Hydraulic Conductance ◽  
Canopy Conductance ◽  
Severe Drought ◽  
Order Of Magnitude

The reactions of sessile oak (Quercuspetraea (Mattuschka) Liebl.) to drought were studied under natural conditions in a 32-year-old stand near Nancy (northeastern France) during the summers of 1989 (strongly rain deficient) and 1990. A plot of five trees was subjected to imposed water shortage, while a group of irrigated trees was used as a control. Measurements of xylem sap flows and water potential enabled the computation of plot transpiration, canopy conductance, and specific hydraulic conductance in the soil–tree continuum. Stomatal conductance was measured directly with a porometer. Specific hydraulic conductance of our oaks was of the same order of magnitude as that reported for other species. It decreased significantly during spring because of a time lag between cambial growth and leaf area expansion. Measured transpiration was close to potential evapotranspiration, except during days with high vapor pressure deficits, which promoted stomatal closure in the absence of soil water deficits. Imposed drought caused predawn leaf water potentials to reach values as low as −2.0 MPa and a progressive decline in hydraulic conductance, which was probably attributable to modifications in hydraulic properties at the soil–root interface. This gradual decline in conductance was attributed to their deep rooting (1.40 m). This study revealed that Q. petraea may be considered as drought tolerant because of adaptations like deep rooting, efficient and safe xylem sap transport, maintenance of significant stomatal conductance, and significant transpiration, even during strong drought stress.

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