scholarly journals The Regulation of Stomatal Aperture in Tobacco Leaf Epidermal Strips I. The Effect of Ions

1970 ◽  
Vol 23 (4) ◽  
pp. 961 ◽  
Author(s):  
DA Thomas
Keyword(s):  
Flow Rate ◽  
Stomatal Opening ◽  
Stomatal Aperture ◽  
Bathing Solution ◽  
Saturation Curve ◽  
Bathing Medium ◽  
Simple Apparatus ◽  
Similar Shape ◽  
Maximal Opening ◽  
Opening And Closing

A simple apparatus has been developed whereby the extent of stomatal opening on isolated epidermal strips can be monitored by measuring the flow rate of bathing solution through the stomata. This apparatus has been used to study the opening and closing response of stomata to various treatments. A supply of ions, particularly K+, was found necessary to initiate and maintain the opening of stomata in the light. In the presence of K+ stomata could be opened in the light and closed in the dark. This cycle could be repeated. The pattern of stomatal opening in the light and closing in the dark showed a similar shape with time to that shown for stomata on leaves. Similar results could be obtained in a bathing medium consisting of KH2P04-Na2HP04 buffer. The best pH found for opening was 8� O. No specificity of stomatal opening was found for the anion associated with K +. The addition of Ca2+ or Mg2+ to the bathing medium caused reductions in aperture. The extent of stomatal opening in response to the concentration of K+ in the range 0-10 mM gave a saturation curve with a concentration for half maximal opening of O� 32 mM. Increasing the concentration of K+ past 10 mM resulted in reductions of aperture.

scholarly journals The Regulation of Stomatal Aperture in Tobacco Leaf Epidermal Strips

1972 ◽  
Vol 25 (5) ◽  
pp. 877 ◽  
Author(s):  
DA Thomas
Keyword(s):  
Guard Cell ◽  
Cell Membranes ◽  
Guard Cells ◽  
Stomatal Opening ◽  
Stomatal Aperture ◽  
Bathing Solution ◽  
Bathing Medium ◽  
Tobacco Leaf ◽  
Phosphoenol Pyruvate

Stepwise decreases in the stomatal aperture of tobacco leaf epidermal strips followed stepwise increases in the concentration of KHCOa added to bathing solutions. Removal of KHCOa from the bathing solution resulted in a rapid increase in aperture. The reduction in aperture caused by KHCO., both in the light and dark, can be reversed by the addition of ATP or phosphoenol pyruvate to the bathing solution. The stomatal opening, supported by a NaCl bathing medium, is reduced by the addition of NaHCOa? From the results it is suggested that HCO;/C02t increases the permeability of guard cell membranes causing a net efflux of water or ions or both from the guard cells.

scholarly journals The Regulation of Stomatal Aperture in Tobacco Leaf Epidermal Strips II. The Effect of Ouabain

1970 ◽  
Vol 23 (4) ◽  
pp. 981 ◽  
Author(s):  
DA Thomas
Keyword(s):  
Transport System ◽  
Stomatal Opening ◽  
Stomatal Aperture ◽  
Excitable Cells ◽  
Bathing Medium ◽  
Transport Atpase ◽  
Low Concentrations ◽  
Membrane Bound ◽  
The Times ◽  
K Transport

The K+-dependent, light-stimulated opening of stomata on tobacco and V icia faba epidermal strips was found to be rapidly reduced by low concentrations of ouabain. On removing ouabain stomatal aperture rapidly increased. This suggests that the influx of K+ into the guard cells is associated with a membrane�bound transport ATPase. Experiments with 10-5M p.chloromercuribenzoate (PCMB) and ouabain indicate that the considered transport ATPase is not markedly affected by PCMB. The stomatal opening obtained in the presence of Na+ alone is also decreased on the addition of ouabain, though ouabain does not prevent the longer-term stomatal opening which occurs in the dark in the presence of N a + alone. In the light, recovery of stomatal opening on the removal of ouabain from the bathing medium only occurred in the presence of K+. It is considered that an ATPase�linked K+ transport system could give the rapid rate of influx that would be necessary to bring about stomatal opening in the times observed. The presence of an ATPase transport system would give an evolutionary link between the stomatal control mechanism and that associated with the function of other excitable cells such as nerve and muscle.

scholarly journals Research on a Piezoelectric Pump with Flexible Valves

2021 ◽  
Vol 11 (7) ◽  
pp. 2909
Author(s):  
Weiqing Huang ◽  
Liyi Lai ◽  
Zhenlin Chen ◽  
Xiaosheng Chen ◽  
Zhi Huang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Fluid Transport ◽  
Smooth Transition ◽  
Driving Voltage ◽  
Piezoelectric Pump ◽  
Venous Valve ◽  
Output Pressure ◽  
Small Flow ◽  
Working Principle ◽  
Opening And Closing

Imitating the structure of the venous valve and its characteristics of passive opening and closing with changes in heart pressure, a piezoelectric pump with flexible valves (PPFV) was designed. Firstly, the structure and the working principle of the PPFV were introduced. Then, the flexible valve, the main functional component of the pump, was analyzed theoretically. Finally, an experimental prototype was manufactured and its performance was tested. The research proves that the PPFV can achieve a smooth transition between valved and valveless by only changing the driving signal of the piezoelectric (PZT) vibrator. The results demonstrate that when the driving voltage is 100 V and the frequency is 25 Hz, the experimental flow rate of the PPFV is about 119.61 mL/min, and the output pressure is about 6.16 kPa. This kind of pump can realize the reciprocal conversion of a large flow rate, high output pressure, and a small flow rate, low output pressure under the electronic control signal. Therefore, it can be utilized for fluid transport and pressure transmission at both the macro-level and the micro-level, which belongs to the macro–micro combined component.

The Performance Simulation of One-Way Inlet Valve of Reflux Scavenging Free Piston Engine

2013 ◽  
Vol 694-697 ◽  
pp. 582-587
Author(s):  
Zhen Xin Li ◽  
Zhao Cheng Yuan ◽  
Jia Yi Ma ◽  
Shi Yu Li
Keyword(s):  
Flow Rate ◽  
Spring Constant ◽  
Air Flow Rate ◽  
Inlet Valve ◽  
Free Piston ◽  
Performance Simulation ◽  
Bottom Dead Center ◽  
Free Piston Engine ◽  
Opening And Closing ◽  
Stroke Engine

The performance of one-way inlet valve directly impacts the effect of the reflux scavenging two-stroke engine intake. It’s discovered that the intake air flow rate, the weight of valve and the spring constant have the greatest impact on the opening, closing and the lift change of one-way inlet valve, by simulating the movement of piston and valve using CFD software. The greater the flow rate, the smaller the weight of valve, or the smaller the spring constant, then the faster the opening of valve. Meanwhile, in order to ensure that the valve quickly returns, the bigger of spring constant is the better. The phases of opening and closing of valve lag fall behind the phases of piston getting to bottom dead center (BDC) and top dead center (TDC).

The Theoretical Volumetric Displacement of a Check-Valve Type, Digital Displacement Pump

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Noah Manring ◽  
Christopher Williamson
Keyword(s):  
Bulk Modulus ◽  
Flow Rate ◽  
Modulus Of Elasticity ◽  
Check Valve ◽  
Volumetric Flow Rate ◽  
Theoretical Explanation ◽  
Residual Volume ◽  
Displacement Pump ◽  
Opening And Closing ◽  
Piston Chamber

This paper has been written to develop closed-form equations for describing the theoretical displacement of a check-valve type, digital displacement pump. In theory, the digital displacement pump is used to alter the apparent volumetric displacement of the machine by short circuiting the flow path for reciprocating pistons within the machine that would ordinarily deliver a full volumetric flow rate to the discharge side of the pump. The short circuiting for the pistons is achieved by opening and closing a digital valve connected to each piston chamber at a desired time during the kinematic cycle for each reciprocating piston. Experience with these machines has shown that the expected volumetric displacement for the machine tends to decrease with pressure. This paper presents a theoretical explanation for the reduced volumetric displacement of the pump and quantifies the expected behavior based upon the digital valve command, the residual volume of fluid within a single piston chamber, and the fluid bulk modulus-of-elasticity. In summary, it shown that the apparent volumetric displacement of the machine may be reduced by as much as 10% for high-displacement commands and by as much as 30% for low-displacement commands.

The Sensitivity of the Pedal Ganglion of the Slug to Osmotic Pressure Changes

1956 ◽  
Vol 33 (3) ◽  
pp. 493-501
Author(s):  
G. A. KERKUT ◽  
B. J. R. TAYLOR
Keyword(s):  
Osmotic Pressure ◽  
Ionic Concentration ◽  
The Body ◽  
Bathing Solution ◽  
Pedal Ganglion ◽  
Bathing Medium ◽  
Rates Of Change ◽  
Fluid Concentration ◽  
Locke Solution ◽  
Pressure Changes

1. The effects of different dilutions of Locke solution on the electrical activity of the isolated pedal ganglion of the slug can be reproduced by adding different concentrations of glucose of mannitol to a given concentration of Locke. 2. This indicates that certain cells in the pedal ganglion are sensitive to the osmotic pressure of the solution and not its ionic concentration. 3. The preparation is sensitive to slow changes in the concentration of the bathing medium. The cells increased their activity when the bathing solution was slowly changed from 0.7 Locke to 0.6 Locke, the change taking 43 min. This corresponds approximately to a change of 1% of the body fluid concentration over 4 min. Such rates of change are found in the normal intact animal. 4. The sensitivity of the preparation compares well with that of the mammalian osmoreceptors.

Recovery of Transmembrane Potentials in Plants Resistant to Aryloxyphenoxypropanoate Herbicides: A Phenomenon Awaiting Explanation

Weed Science ◽  
1994 ◽  
Vol 42 (2) ◽  
pp. 293-301 ◽  
Author(s):  
Joseph A. M. Holtum ◽  
Rainer E. Häusler ◽  
Malcolm D. Devine ◽  
Stephen B. Powles
Keyword(s):  
Plasma Membrane ◽  
Single Gene ◽  
Membrane Vesicles ◽  
Bathing Solution ◽  
Root Tips ◽  
Plasma Membrane Vesicles ◽  
Bathing Medium ◽  
Transmembrane Potentials ◽  
Wild Oats ◽  
Rigid Ryegrass

Aryloxyphenoxypropanoate (APP) herbicides, such as diclofop, depolarize membranes in parenchyma cells of coleoptiles and root tips, and isolated tonoplast or plasma membrane vesicles from a variety of plant species. Some APP-resistant biotypes of rigid ryegrass and wild oat repolarize membranes after removal of herbicide from a bathing medium. The repolarization ability does not require presence of either APP-insensitive acetyl coenzyme A carboxylase or an increased capacity for herbicide detoxification. The kinetics of depolarization and repolarization depend upon the herbicide, the herbicide concentration, the biotype, and the pH of the bathing solution. For rigid ryegrass, depolarization in the presence of diclofop acid is more rapid than in the presence of diclofop-methyl, and 50% depolarization required about 4 μM diclofop acid. Both the nonherbicidal S(–) and the herbicidal R(+) enantiomers of diclofop acid depolarized membranes in susceptible and resistant ryegrass. Susceptible biotypes regenerated transmembrane potentials following removal of the S(–) but not the R(+) enantiomer, whereas resistant biotypes repolarized following exposure to either enantiomer or a mixture of the two. The herbicide 2,4-D affected, in a complex manner, the ability of both susceptible and resistant ryegrass biotypes to depolarize and repolarize. It is postulated that the intracellular concentration of diclofop acid in susceptible and resistant plants is not the same due to differences in the partitioning of diclofop acid between the extracellular spaces and the cytoplasm. The mechanism producing the postulated difference is unknown, but observations on the proton extrusion capacity of both ryegrass and wild oats, the responses of ryegrass to [K+] and PCMBS, and the single-gene inheritance pattern of resistance in wild oats indicate that changes in the diclofop sensitivity of a plasma membrane protein involved in the generation of proton or ion gradients may be involved.

Hydraulic Circulation Test and CFD Analysis of Prestressed Cementing Unit Earth Anchor

2014 ◽  
Vol 1006-1007 ◽  
pp. 156-159
Author(s):  
Ding Li
Keyword(s):  
Flow Rate ◽  
Discharge Coefficient ◽  
Drilling Fluid ◽  
Critical Value ◽  
Thermal Recovery ◽  
Differential Pressure ◽  
Cfd Analysis ◽  
Fluid Flow Rate ◽  
Casing Pipe ◽  
Opening And Closing

In the process of thickened oil thermal recovery, the pre-stress cementing needs to be anchored at the bottom of the casing pipe. And the reliable opening and closing of anchor flukes directly influence the anchoring. In allusion to the problems of how to get the critical value of drilling fluid flow rate of when the anchor flukes begin to open, completely open, begin to close and completely close, whether different nozzles can open or close reliably, getting the corresponding differential pressure and discharge coefficient of the different nozzles, this paper conducts a study from both theory and experiment to obtain the relevant parameters. By simulating the anchor in actual work and dealing with the data, we conclude that: (1) The fluke can open smoothly when the flow rate reaches a certain flow and it can also close smoothly when the flow rate declines. (2) The critical flow rate of the flukes, when two kinds of anchors are with different nozzles, has been acquired. (3) Corresponding differential pressure and discharge coefficient of the different nozzles in different flow rate have been ascertained.

scholarly journals Evaluation of the Influence of the Supply Pressure on Functional Parameters of the Impulse Low-Pressure Gas-Phase Injector

2020 ◽  
Vol 14 (4) ◽  
pp. 180-185
Author(s):  
Dariusz Szpica ◽  
Andrzej Borawski ◽  
Grzegorz Mieczkowski ◽  
Michał Kusznier ◽  
Mohamed M. Awad ◽  
...  
Keyword(s):  
Gas Phase ◽  
Flow Rate ◽  
Volumetric Flow Rate ◽  
Low Pressure ◽  
Closing Time ◽  
Functional Parameters ◽  
Functional Relationships ◽  
Supply Pressure ◽  
Indirect Evaluation ◽  
Opening And Closing

Abstract The article presents research results referring to the influence of supply pressure on the functional parameters of the impulse low-pressure gas-phase injector. The study was done on the original stand for flow test of gas-phase injectors. In the indirect evaluation, with the initial parameters and the length of the forced impulse, the current line, acceleration and pressure sensor courses were used. Apart from the volumetric flow rate, the analysed parameters were the time periods of the injector opening and closing process. Those time segments were composed of response time and opening/closing time, the sum of which gives time of full opening. Functional relationships describing the volumetric flow rate, time of full opening and closing are presented, which are helpful not only in comparative tests of different injectors, but also in modelling the operation of gas injector or algorithms of gas supply control system. The reference to the volumetric flow rate allowed to indicate possible causes of variability of this parameter depending on the supply pressure.

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