Ion Distribution in Roots of Barley Seedlings Measured by Electron Probe X-Ray Microanalysis

Pitman, M. G.; Läuchli, André; Stelzer, Robert S.

doi:10.1104/pp.68.3.673

Cited by 92 publications

(38 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This volume is a function of the electron beam accelerating voltage, the average atomic number of the elements in the sample, and the atomic number of the element analyzed. At an accelerating voltage of 10 kV, the excitation volume in frozen hydrated tissue for Na+ and K+ (as well as other elements of similar atomic number) has been estimated to be 2 to 3 ,um in diameter (18).…”

Section: Resultsmentioning

confidence: 99%

“…Also, it is possible that in some instances the excited volume for Na extended into the vacuole resulting in a larger xray signal and the perception of greater Na contents in the cytoplasm. Since the excited volume for Cl would be smaller than for Na (18), cytoplasmic Cl content should be resolved more accurately than the Na content. However, if this had been the case, it is likely that problems with excited volume overlap would have resulted in much greater variability from analysis to analysis than was observed.…”

Section: Resultsmentioning

confidence: 99%

“…Cell suspensions of Nicotiana tabacum L. var Wisconsin 38, adapted to different concentrations of NaCl (up to 600 mM), were maintained according to procedures described previously (1). Unadapted 7 ,um in diameter, at an accelerating voltage of 10 kV the limits of resolution are estimated to be 2-3,m [18]), and a relatively even surface across the cell so that the topography at the various points of analysis would be consistent.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Binzel¹,

Hess²,

Bressan³

et al. 1988

Plant Physiol.

245

129

View full text Add to dashboard Cite

Na+ and Cl-are the principal solutes utilized for osmotic adjustment in cells of Nicotiana tabacum L. var Wisconsin 38 (tobacco) adapted to NaCi, accumulating to levels of 472 and 386 millimolar, respectively, in cells adapted to 428 millimolar NaCI. X-ray microanalysis of unetched frozen-hydrated cells adapted to salt indicated that Na+ and Cl-were compartmentalized in the vacuole, at concentrations of 780 and 624 millimolar, respectively, while cytoplasmic concentrations of the ions were maintained at 96 millimolar. The morphometric differences which existed between unadapted and salt adapted cells, (cytoplasmic volume of 22 and 45% of the cell, respectively), facilitated containment of the excited volume of the x-ray signal in the cytoplasm of the adapted cells. Confirmation of ion compartmentation in salt adapted cells was obtained based on kinetic analyses of 22NaI and 36CI-efflux from cells in steady state. These data provide evidence that ion compartmentation is a component of salt adaptation of glycophyte ceUs.A typical response of many plants to saline environments, particularly halophytes, is to accumulate high intracellular concentrations of Na+ and Cl- (9,11,23,26,28). Since the in vitro activities of enzymes isolated from glycophytes or halophytes are inhibited equally by NaCl (9, 11), it has been generally accepted that the accumulated ions are sequestered in the vacuole and 'compatible solutes,' such as sugars, proline, and glycinebetaine, function to balance the osmotic pressure of the cytoplasm (9,11,26). This ability to compartmentalize Na+ and Cl-has been considered to be a mechanism of tolerance of halophytes (26).Although salt tolerance of glycophytes, particularly agronomic species, is usually attributed to the ability to exclude Na+ and Cl-, especially from the shoot (8, 11), intracellular ion compartmentation also may occur in these species. Despite indications of negative correlations between ion accumulation and salt tolerance in glycophytes, such as tomato (22), rice (29), wheat (27), and maize (12), examination of the data reveals that, even in tolerant genotypes, the accumulated levels of Na+ and Clare substantial. In some instances whole cell Na+ and Cl-accumulation was similar for both tolerant and sensitive genotypes (22,27,29). Thus, the ability to compartmentalize Na+ and Clmay be an underlying determinant of the tolerance not only of halophytes but also of many crop species.Verification of ion compartmentation has been restricted by the difficulty in obtaining reliable measurements of subcellular ion concentrations (7,15,23,30). Despite this, cytoplasmic Na + concentration in leaf cells of Suaeda maritima was determined to be 165 mm by efflux analysis when the whole cell concentration was about 600 mM (28). Data obtained by x-ray microanalysis of frozen hydrated leaves of Atriplex spongiosa (23) revealed that cytoplasmic ion concentrations were considerably lower than those in the vacuole.Results from investigations of glycophytes exposed to salinity have been less conc...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Binzel¹,

Hess²,

Bressan³

et al. 1988

Plant Physiol.

245

129

View full text Add to dashboard Cite

show abstract

“…Multiple mechanisms, including morphological and biochemical adaptations, are probably involved in maintaining this low cytoplasmic Na+/K+ ratio. In barley (Hordeum vulgare), two such mechanisms are extrusion of Na+ into the vacuole across the tonoplast membrane and extrusion of Na+ into the external medium across the plasma membrane (13,16). The energy for Na+ extrusion could be provided by the proton gradients generated by the plasma membrane or tonoplast H+-ATPases.…”

mentioning

confidence: 99%

Rapid Induction of Na⁺/H⁺ Exchange Activity in Barley Root Tonoplast

Garbarino¹,

DuPont²

1989

Plant Physiol.

101

View full text Add to dashboard Cite

Na+/H exchange activity in barley (Hordeum vulgare cv CM-72) root tonoplast was induced by Na+ even in the presence of inhibitors of protein synthesis. Induction occurred with a half-time of only 15 minutes. When salt-treated roots were transferred to a nutrient solution containing no Nat, the activity disappeared with a similar time course. The data suggest that Na+/H+ exchange was due to activation of an existing protein rather than to de novo protein synthesis.Buildup of salts in the soil is a major problem on irrigated farmland and in semiarid regions where winter rainfall is not sufficient to flush accumulated salts from the top soil (18). To grow in saline soils, plants must maintain a much lower ratio of Na+/K+ in their cytoplasm than is present in their surroundings (10,13,14). Multiple mechanisms, including morphological and biochemical adaptations, are probably involved in maintaining this low cytoplasmic Na+/K+ ratio. In barley (Hordeum vulgare), two such mechanisms are extrusion of Na+ into the vacuole across the tonoplast membrane and extrusion of Na+ into the external medium across the plasma membrane (13, 16). The energy for Na+ extrusion could be provided by the proton gradients generated by the plasma membrane or tonoplast H+-ATPases. Recently, using the tonoplast ATPase to generate the H+ gradient, we discovered a Na+/H+ exchange in vesicles from a tonoplast-enriched fraction isolated from barley roots (9). Na+/H+ antiports have also been reported in tonoplast fractions from red beet (Beta vulgaris) (2) and sugar beet (3). The Na+/H+ exchange activity in cell suspension cultures of sugar beet, a halophyte, was partly constitutive (3). In contrast, that of barley, a relatively salt-tolerant glycophyte, was undetectable unless the plants were grown in the presence of Na+. In this paper, induction of the tonoplast Na+/H+ exchange activity in barley is characterized in more detail. MATERIALS AND METHODS Plant MaterialA salt-tolerant cultivar of barley, Hordeum vulgare L. cv CM-72 (1), was grown as described previously (7) Membrane PreparationsA tonoplast-enriched membrane fraction was isolated as described previously (6, 9). Roots (10 gm) were excised into ice water, rinsed, and then ground in homogenization buffer (67 mL) containing 250 mm sucrose, 50 mm Tris, 8 mM EDTA, and 4 mm DTT (pH 8.0). The fraction collected from the 22/30% interface of a sucrose step gradient was washed and resuspended in buffer containing 250 mM sorbitol, 1 mM DTT, and 5 mm Mes adjusted to pH 7.0 with Tris. Aliquots containing 0.5 to 1.5 mg protein/mL were stored at -70C. Enzyme AssaysThe generation and dissipation of pH gradients across the membrane vesicles were followed by measuring quenching and recovery of acridine orange fluorescence as described previously (6,9

show abstract

“…A high external salt concentration is detrimental to many plants due to (1) a decrease of the external water potential, and (2) the accumulation of Na and Cl in the plant cytoplasm, which can cause an inhibition of metabolic processes. Pitman et al (1981) found high concentrations of Na in the vacuole after salt stress and suggested that sequestration of Na into plant vacuoles prevents a toxic accumulation of this element in the cytosol. In salt tolerant wild-turf roots an increase in inorganic phosphate in vacuoles after salt stress has also been observed (Takagishi et al, 1991).…”

Section: mentioning

confidence: 99%

Subcellular compartmentation of elements in non‐mycorrhizal and mycorrhizal roots of Pinus sylvestris: an X‐ray microanalytical study. II. The distribution of calcium, potassium and sodium

Bücking

Heyser

2000

New Phytologist

View full text Add to dashboard Cite

The inter‐ and intracellular distribution of the elements calcium, potassium and sodium in non‐mycorrhizal and mycorrhizal roots of Pinus sylvestris dependent on different external nutrient supply conditions was detected by energy‐dispersive X‐ray microanalysis after cryofixation, freeze‐drying and pressure infiltration of the material. In non‐mycorrhizal and mycorrhizal roots, calcium was mainly detectable in the apoplastic regions. The levels in vacuoles and cytoplasm were near the limits of detection by X‐ray microanalysis. Incubation with high concentrations of potassium and sodium, or mycorrhizal infection with Suillus bovinus and Pisolithus tinctorius reduced the amounts of calcium detectable in the roots, especially in the apoplast of cortical cells. The studies revealed that: potassium is mainly localized in cytoplasm and cell walls; the cytoplasmic content is regulated over a wide range of external potassium concentrations; potassium levels in the inner parts of roots are higher than in the outer parts. Mycorrhizal infection with Suillus bovinus had no effect on the inter‐ and intracellular distribution of potassium in roots but, if the external supply was low, the potassium content in shoots was reduced. In non‐mycorrhizal pine roots and those infected with Paxillus involutus an increase in the sodium content of all cell compartments was observed after treatment with high external concentrations of NaH2PO4. However, an increase in sodium content in mycorrhizas of S. bovinus was not detected. The X‐ray microanalytical results are discussed in relation to the apoplastic movement of nutrients in non‐mycorrhizal and mycorrhizal fine roots of pine and to the demand for these nutrients in different intracellular compartments.

show abstract

Ion Distribution in Roots of Barley Seedlings Measured by Electron Probe X-Ray Microanalysis

Cited by 92 publications

References 5 publications

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Rapid Induction of Na⁺/H⁺ Exchange Activity in Barley Root Tonoplast

Subcellular compartmentation of elements in non‐mycorrhizal and mycorrhizal roots of Pinus sylvestris: an X‐ray microanalytical study. II. The distribution of calcium, potassium and sodium

Contact Info

Product

Resources

About

Ion Distribution in Roots of Barley Seedlings Measured by Electron Probe X-Ray Microanalysis

Cited by 92 publications

References 5 publications

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Intracellular Compartmentation of Ions in Salt Adapted Tobacco Cells

Rapid Induction of Na+/H+ Exchange Activity in Barley Root Tonoplast

Subcellular compartmentation of elements in non‐mycorrhizal and mycorrhizal roots of Pinus sylvestris: an X‐ray microanalytical study. II. The distribution of calcium, potassium and sodium

Contact Info

Product

Resources

About

Rapid Induction of Na⁺/H⁺ Exchange Activity in Barley Root Tonoplast