The Use of Short-Term and Quasi-Steady Influx in Estimating Plasmalemma and Tonoplast Influx in Barley Root Cells at Various External and Internal Chloride Concentrations

Cram, W. J.; Gg, Laties

doi:10.1071/bi9710633

Cited by 72 publications

(25 citation statements)

References 21 publications

(32 reference statements)

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“…That steady-state potassium content in illuminated stomata resulted from reduced influx into the vacuole rather than stimulated efflux is in agreement with most studies of excised roots systems (Pitman, Courtice, and Lee 1968;Cram and Laties 1971). Reduced influx combined with low efflux would seem an efficient way of maintaining internal ion concentration (Cram and Laties 1971). Again the closest parallel to stomata may be the osmotic pressure regulatory system of Valonia ventricosa described by Gutknecht (1968).…”

Section: Disoussionsupporting

confidence: 73%

Aspects of Potassium Accumulation by Stomata of Vicla Faba

Fischer¹

1972

Aust. Jnl. Of Bio. Sci.

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Potassium accumulation by guard cells during the light opening of V. Jaba stomata in epidermal strips was determined quantitatively with 42K and 86Rb tracers. The sodium cobaltinitrite stain for potassium was also used. Particular attention was paid to errors arising from the presence of intact epidermal cells.When epidermal strips obtained from darkened leaves were floated on potassium chloride solution (usually 10 mM) in light plus C02-free air, guard cell potassium content and stomatal aperture increased in parallel, both approaching a maximum after about 300 min. Flux measurement suggested that the steady maximum potassium content (and aperture) arises because of a decline in the initially high potassium influx. With opening of stomata in the light, external calcium reduced in a parallel manner both opening and potassium uptake at potassium concentrations ranging from nearly zero to 50 mM. Also, maximum stomatal opening and potassium accumulation in the presence or absence of calcium bore linear relationships to log external potassium concentration. These results are discussed in relation to potassium accumulation in other plant systems.In experiments with epidermal strips, guard cell potassium content showed a consistent linear relationship to stomatal aperture. For 16 experiments spanning two years and many treatments affecting aperture, the mean slope of this relationship was 2·6 nmoles cm-2 p.m-l. This is equivalent to a change in potassium concentration of 40 mM p.m-l. The increase in guard cell osmotic pressure attributable to potassium plus anion accumulation is estimated to be 1·5 bars p.m-l, which is a major portion of the observed increase in osmotic pressure with opening (2, 0 bars p.m-l).

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Section: Disoussionsupporting

confidence: 73%

Aspects of Potassium Accumulation by Stomata of Vicla Faba

Fischer¹

1972

Aust. Jnl. Of Bio. Sci.

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“…The present results are relevant to this controversy. The absorption period for 4K by oat roots was 30 min which is sufficiently long enough for transport to have occurred across both the plasma membrane and tonoplast (5). Now, if the ATPase is involved in ion transport, and the results discussed above support this interpretation, then K+ activation of this plasma membrane enzyme throughout the concentration range of mechanisms I and II (i.e.…”

Section: Discussionsupporting

confidence: 62%

Characterization of Plasma Membrane-associated Adenosine Triphosphase Activity of Oat Roots

Leonard¹,

Hodges²

1973

Plant Physiol.

207

121

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Based on high correlations between membrane-bound ATPase activities and ion absorption rates of several plant species (9-11, 29), it was suggested that an ATPase mediates energy transfer to the ion transport system. This proposal was strengthened by the demonstration that the monovalent ionstimulated ATPase is associated with the plasma membrane of oat roots (19,20).The purified plasma membrane ATPase is specific for ATP, requires Mg" and is further activated by monovalent ions 'This research was supported by a grant from the National Science Foundation (GB-31052X (19,20,28). In this paper the enzyme is further characterized with respect to its requirements for ATP, Mg2+, and KCI. The kinetics of KCl stimulation of the plasma membrane ATPase of oat roots were virtually identical to the kinetics of K+ influx into oat roots, both of which are best described by a single isotherm with continually changing kinetic parameters. MATERIALS AND METHODSPlasma membranes were isolated from oat (Avena sativa L. cv. Goodfield) roots as previously described (19,20). Briefly, about 50 g of 6-day-old roots were excised, washed in cold deionized water, and ground (mortar and pestle) in 200 ml of a medium consisting of 0.25 M sucrose, 0.003 M EDTA, 2.5 mm dithiothreitol, and 0.025 M tris-MES, pH 7.2. The homogenate was strained through cheesecloth and successively centrifuged at 13,000g for 15 min and 80,000g for 30 min. The 13,000 to 80,000g pellet was suspended in 30 ml of fresh grinding medium, pelleted. suspended in 2.5 ml of 20% (w/w) sucrose containing 1 mM MgSO4 and 1 mm tris-MES, pH 7.2, and 2 ml were layered onto a 36-ml discontinuous gradient consisting of 28 ml of 45%4o (w/w) and 8 ml of 34% sucrose in 1 mM MgSO, and 1 mm tris-MES, pH 7.2 (Mg2+ was omitted from the gradient for experiments involving Mg2+ as a variable). The gradient was centrifuged for 2 hr at 95,000g in a Spinco SW 27 rotor. The membranes collecting at the 34 to 45% sucrose interface are more than 75% plasma membranes (20).ATPase activity was measured at 38 C in a 1-ml volume containing 3 mm ATP (tris salt) at desired pH, 33 mm tris-MES at desired pH and variable amounts of mono-and divalent ions

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“…Independent estimates of plasma membrane and tonoplast influx for chloride uptake by barley roots point to the rate controlling influence of the tonoplast at high external concentrations (5). That is, at high concentrations permeation of the surface membrane ceases to be rate-limiting (see 5,16). Whether the foregoing applies to glucose transport remains to be determined.…”

mentioning

confidence: 99%

“…Vol. 51,1973 the highest range may (although need not) reflect kinetics of glucose transport to the vacuole (5). Independent estimates of plasma membrane and tonoplast influx for chloride uptake by barley roots point to the rate controlling influence of the tonoplast at high external concentrations (5).…”

mentioning

confidence: 99%

“…For certain ions at least, plasma membrane and tonoplast influx have been separately estimated (5). Whereas legs of a multiple isotherm may in certain instances reflect events at different membranes, an alternative explanation for multiphasic isotherms within a moderate spread of external concentrations is based on an all-or-none or association-induction change in state of a given transport barrier in response to critical solute concentrations in the environment (see Ling [18]; Nissen [22]).…”

mentioning

confidence: 99%

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