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 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 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 CATION TRANSPORT IN YEAST

1956 ◽  
Vol 39 (5) ◽  
pp. 687-704 ◽  
Author(s):  
Ernest C. Foulkes
Keyword(s):  
Cell Membrane ◽  
Dissociation Constant ◽  
Concentration Gradient ◽  
Cation Transport ◽  
K Uptake ◽  
Present Evidence ◽  
Inhibitor Complex ◽  
Maximum Value ◽  
Low Concentrations ◽  
K Transport

1. The distribution of azide added to suspensions of bakers' yeast was studied under various conditions. The recovery of azide was estimated in the volume of water into which low concentrations of electrolytes can readily diffuse (anion space). Considerable azide disappeared from this anion space. 2. The incomplete recovery of azide in the anion space is due to its uptake by the cells. This uptake occurs against a concentration gradient at 0°C., and is attributed to binding of azide by cell constituents. 3. Confirmatory evidence is presented that one such constituent is the K carrier in the cell membrane. The azide inhibition of K transport is not mediated by inhibition of cytochrome oxidase in the mitochondria. 4. From the amount of combined azide and the experimentally determined dissociation constant of the K carrier-inhibitor complex, the maximum value for the concentration of this carrier is calculated as 0.1 µM/gm. yeast. 5. The addition of glucose and PO4 causes a secondary K uptake which is not azide-sensitive and is clearly distinct from the primary, azide-sensitive mechanism. 6. The existence of a separate carrier responsible for Na extrusion is reconsidered. It is concluded that present evidence does not necessitate the assumption that such a carrier is active in yeast.

scholarly journals Influx and accumulation of Cs+ by the akt1 mutant of Arabidopsis thaliana (L.) Heynh. lacking a dominant K+ transport system

2001 ◽  
Vol 52 (357) ◽  
pp. 839-844 ◽  
Author(s):  
Martin R. Broadley ◽  
Abraham J. Escobar‐Gutiérrez ◽  
Helen C. Bowen ◽  
Neil J. Willey ◽  
Philip J. White
Keyword(s):  
Arabidopsis Thaliana ◽  
Transport System ◽  
K Transport

Ouabain-sensitive liver and diaphragm respiration in cold-acclimated hamster

1977 ◽  
Vol 42 (2) ◽  
pp. 150-153 ◽  
Author(s):  
B. A. Horwitz ◽  
M. Eaton
Keyword(s):  
Transport System ◽  
Cold Exposure ◽  
Driving Force ◽  
Energy Demands ◽  
Before And After ◽  
Ouabain Inhibition ◽  
K Transport

The in vitro respiratory rates of liver and diaphragm from hamsters were compared before and after prolonged cold exposure (5 degrees C, 3–4 wk). In the presence or absence of glucose, respiratory rates were elevated in both tissues from the cold-acclimated hamsters, and these cold-induced increases were significantly reduced by ouabain. This ouabain inhibition is consistent with the hypothesis that cold exposure of these rodents stimulates the energy demands of the Na+/K+ transport system in liver and diaphragm, with these demands providing a driving force, at least in part, for respiration and accompanying cellular thermogenesis.

Actions of adrenergic agonists on isolated excretory ducts of submandibular glands

1978 ◽  
Vol 235 (6) ◽  
pp. F548-F556 ◽  
Author(s):  
A. R. Denniss ◽  
L. H. Schneyer ◽  
C. Sucanthapree ◽  
J. A. Young
Keyword(s):  
Sympathetic Nerve Activity ◽  
Physiological Changes ◽  
Adrenergic Agonists ◽  
Nerve Activity ◽  
Bathing Medium ◽  
Submandibular Glands ◽  
Low Concentrations ◽  
K Secretion ◽  
Prior Administration

The effects of norepinephrine and isoproterenol on the transepithelial potential difference (PD) and the net transepithelial fluxes of Na, K, Cl, and HCO3 of the main ducts of the submandibular glands of rats and rabbits have been studied by microperfusion of ducts incubated in vitro in an artifical bathing medium. In the rabbit duct, both catecholamines caused depolarization and reduced transepithelial Na reabsorption at concentrations above 10(-29) M. In the rat duct, norepinephrine reduced PD and net Na reabsorption and, in addition, inhibited net K secretion at concentrations of 10(-7) M and above. Isoproterenol also depolarized the duct and reduced net K reabsorption, but at concentrations of 10(-9) M it stimulated net Na reabsorption, whereas at concentrations of 10(-4) M it inhibited Na reabsorption. The stimulation caused by isoproterenol at low concentrations could be blocked by prior administration of propranolol. The results suggest that electrolyte transport, by both rat and rabbit ducts, may be influenced not only by sympathetic nerve activity but also by physiological changes in the concentrations of circulating catecholamines. Inconsistencies in the literature regarding the sensitivity of the rabbit duct to catecholamines and the response of the rat duct to isoproterenol have now been resolved.

The Oligomeric Nature of Na/K-Transport ATPase

2001 ◽  
Vol 129 (3) ◽  
pp. 335-342 ◽  
Author(s):  
K. Taniguchi ◽  
S. Kaya ◽  
K. Abe ◽  
S. Mardh
Keyword(s):  
Transport Atpase ◽  
K Transport

The (Na++K+) activated enzyme system and its relationship to transport of sodium and potassium

1974 ◽  
Vol 7 (3) ◽  
pp. 401-434 ◽  
Author(s):  
Jens Chr. Skou
Keyword(s):  
Transport System ◽  
Enzyme System ◽  
Membrane Bound ◽  
Hydrolysis Of ◽  
Sodium And Potassium

It seems to be the membrane bound (Na++K+)-activated enzyme system which transforms the energy from a hydrolysis of ATP into a vectorial movement of sodium out and potassium into the cell against electrochemical gradients, i.e. this systems seems to be the transport system for sodium and potassium (see, for example, review by Skou, 1972; Hokin & Dahl, 1972).

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