Some Aspects of Chloride Absorption by Bean Leaf Tissue

Jacoby, B.; Plessner, Ora E.

doi:10.1093/oxfordjournals.aob.a084350

Cited by 10 publications

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“…The exponential character of the time course of Cl-uptake by etiolated laminae in the light (Fig. 1) (3,5,7,9).…”

Section: Resultsmentioning

confidence: 99%

Anion Absorption by Etiolated Wheat Leaves after Vacuum Infiltration

MacDonald¹,

Macklon²

1972

Plant Physiol.

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Chloride and phosphate uptake by leaf segments of green and etiolated 7-day-old seedlings of Triticum aestivum L. cultivar Capelle is enhanced by light. In the range from 1.0 to 10 millimolar KCl, maximal rates of uptake were obtained with 1.5-millimeter segments. Above 1.5 millimeters, ion diffusion through the cut edge was the rate-limiting factor, uptake being proportional to the amount of cut edge, but vacuum infiltration of the tissue overcame this limitation, allowing uptake to be independent of segment length. No Leaf samples were placed in flasks containing 25 ml K'Cl or KH,"P04 solution at pH 5.5 and with a specific radioactivity between 10 and 20 ac/liter. The flasks were sealed with Parafilm and agitated at 25 C on reciprocating water bath shakers, at 80 oscillations/min. At the end of the uptake period, each leaf sample was rinsed for 5 min at room temperature. Assay of the counts appearing in rapid changes of distilled water (by counting the washings dried down on planchets) had established that all free space label was removed in less than 3 min. Leaf segments were then placed on planchets spread with 3.6% polyvinyl alcohol, and, after drying, the radioactivity was determined with a gas flow Micromil window detector. Activity in the solutions was determined by placing 0.1 ml on a planchet containing a circle of lens paper spread with a sucrose-detergent solution.For the time course experiments, leaves were cut with scissors to a length of 50 mm, measured from the intact tip to the cut end. Four such leaves weigh about 0.1 g, and usually six or eight laminae were sampled at each time interval. Separate flasks were used for each time interval, and, when readings were required at 3-hr intervals over 24 hr, zero time for half the flasks was staggered by 12 hr.For experiments in the range 0.5 to 25 mm, 50-mm leaf segments were halved and only the proximal halves used. These were cut into 12.5-and 5-mm lengths with a razor blade and into lengths less than 5 mm using a hand microtome in which the segments were supported between potato tuber tissue, the debris from which was rinsed away before placing the leaf segments in the absorption flasks. Sufficient segments were used to give a minimal nominal length per sample of 100 mm. The extent of damage at the cut surface, to be allowed for when expressing uptake in terms of unit length of lamina. was measured under a stereomicroscope. Cells from which the contents were lost extended for about 0.12 mm in from a razor-cut edge and about 0.45 mm in from a scissor-cut edge.Leaf segments were used either "noninfiltrated" or after vacuum infiltration with glass-distilled water. All tissue to be infiltrated was prepared as 50-mm segments. These were submerged in water in a vacuum desiccator which was evacuated several times to a pressure of 20 cm Hg, using a water pump.

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“…The exponential character of the time course of Cl-uptake by etiolated laminae in the light (Fig. 1) (3,5,7,9).…”

Section: Resultsmentioning

confidence: 99%

Anion Absorption by Etiolated Wheat Leaves after Vacuum Infiltration

MacDonald¹,

Macklon²

1972

Plant Physiol.

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“…Experiments on P. vulgaris L. cv. Brittle Wax showed dual isotherms for K+ (Rb+), Na+, and C1-influx (9). Ammonium influx in the algae Hypnea musciformis and Macrocystis pyrifera (4) as a function of external concentration shows a saturable component at low concentrations with a continued increased in influx at higher concentrations; it is not clear if this nonsaturating component of the influx represents nonmediated NH3 entry.…”

Section: Discussionmentioning

confidence: 99%

“…The occurrence of the NH4' uniporter system would permit a more precise control of ammonium (and NH3) concentration in the leaf apoplast than would the occurrence solely of NH3 diffusion. An elegant demonstration of NH4+ transport come from parallel voltage-clamp and net ammonium (methylammonium) flux measurements (25,26) [8], reference to the figures in Jacoby [9], which claims to follow the same technique, suggests a thickness of 0.8 mm). One-hundred-mg portions of randomized slices then were placed in 30-ml screw-topped vials with 10 ml 0.1 mm CaSO4 solution, and the vials were placed in a thermostatted (at 25 C) water bath on a tray shaking at 0.5 Hz, with illumination from above by means of a Xenon arc lamp providing 200 t,E m-2 s-1 at the level of the leaf slices.…”

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confidence: 99%

Methylammonium Transport in Phaseolus vulgaris Leaf Slices

Raven¹,

Farquhar²

1981

Plant Physiol.

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Methylammonium (as a nonmetabolized analog of ammonium) transport was studied in leaf slices of Phaseolus vulgaris L. var. 'Hawkesbury Wonder.' The relationship of influx to external pH (6.0-10.5) shows that the influx at low external pH is a larger fraction of that at high external pH than would be expected from the pK. of methylammonium and the assumption that only CH3NH2 is entering the cells. The relationship between methylammonium influx and external methylammonium concentration shows some evidence of saturation; this is a function of the transport system rather than of the (limited) methylammonium metabolism in the cells. The "equilibrium" concentration ratio for methylammonium between leaf slices and bathing medium is far higher than can be explained by the transport of CH3NH2 alone and the pH of the compartments involved. when all of the nitrate assimilation in nitrate-grown plants occurs in the leaves (2). The immediate application of the work described here relates to the control of gaseous NH3 fluxes between Phaseolus vulgaris leaves and the aerial environment (2). A major determinant of the NH3 concentration in the intracellular gas spaces in equilibrium with the leaf apoplast solution is the ammonium concentration in the cell wall solution; other important factors are the temperature of the leaf and the apoplastic pH.The work reported here deals with the mechanism(s) of ammonium transport at the plasmalemma of leaf of P. vulgaris; the other important parameter (apoplastic pH) will be dealt with elsewhere (J. A. Raven, manuscript in preparation). Work on a wide range of other cell types has shown that, in addition to the unfacilitated movement of NH3 through the lipid portion of the cell membranes, the plasmalemma commonly possesses an NH4' uniporter system (4, 16, 18, 20, 22, 23, 25-27; cf. ref. 13). The NH3 diffusion system on its own leads to an ammonium distribution related to the pH on each side of the membrane. The NH4' uniport leads to an equilibrium distribution related to the electrical potential difference across the membrane; however, the involvement of a specific uniporter permits control of net NH4+ fluxes (and, hence, of ammonium levels in phases of restricted volume separated by the membrane) via induction/repression and feedback inhibition. The occurrence of the NH4' uniporter system would permit a more precise control of ammonium (and NH3) concentration in the leaf apoplast than would the occurrence solely of NH3 diffusion. An elegant demonstration of NH4+ transport come from parallel voltage-clamp and net ammonium (methylammonium) flux measurements (25,26)

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“…However, by us ing thin slices of leaf tissue (59,60,110) this problem can be overcome, and genuine cellular ion absorption is then thought to be observed. It seems fair to speculate on the relative proportion of undamaged cells in such a prepara tion and on the extent to which the results are meaningful, but be that as it may, the dual isotherm pattern of ion uptake bas been reported in several tissues.…”

Section: Ion Transport In Various Plant Tissuesmentioning

confidence: 99%

Ion Transport in the Cells of Higher Plant Tissues

Anderson

1972

Annu. Rev. Plant. Physiol.

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Some Aspects of Chloride Absorption by Bean Leaf Tissue

Cited by 10 publications

References 0 publications

Anion Absorption by Etiolated Wheat Leaves after Vacuum Infiltration

Anion Absorption by Etiolated Wheat Leaves after Vacuum Infiltration

Methylammonium Transport in Phaseolus vulgaris Leaf Slices

Ion Transport in the Cells of Higher Plant Tissues

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