pH‐related changes in maize root plasma membranes

Suhayda, Charles G.; Weis, Christopher; Shi, Baojun; Haug, A.

doi:10.1080/00103628809368003

Cited by 4 publications

(3 citation statements)

References 15 publications

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“…Decrease in K + net-efflux could be mediated through modifications of plasma-membrane characteristics such as reduced membrane fluidity and permeability. Suhayda et al (1988) showed increased membrane viscosity at low pH which induced a higher K + net-efflux. A1 could displace membrane-bound H + and reverse the damaging effect of high H + concentrations.…”

Section: Discussionmentioning

confidence: 98%

Effect of aluminium on membrane properties of soybean (Glycine max) cells in suspension culture

Sta�

Horst

1995

Plant Soil

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Short-term responses of soybean (Glycine max) cells to aluminium (AI) were studied in suspension culture. Formation of callose was the most sensitive indicator of AI effects. As low as 5 jaM A1 induced callose formation and an increase in callose concentration could be measured as early as 15 min after beginning the AI treatment.Also membrane permeability was rapidly affected by AI. Potassium net-efflux was reduced by increasing A1 concentrations up to 300/~M A1. Increasing the pH of the external solution from 4.3 to 5.3 enhanced callose formation, indicating more severe A1 damage at pH 5.3, which is in agreement with a model on H + amelioration of AI toxicity. A1 did not initiate or enhance ferrous sulfate (FeSO4)-promoted lipid peroxidation. The results indicate that the plasma membrane is a primary target of A1 and that cell suspension culture is a powerful tool to study effects of A1 on plant roots.

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Section: Discussionmentioning

confidence: 98%

Effect of aluminium on membrane properties of soybean (Glycine max) cells in suspension culture

Sta�

Horst

1995

Plant Soil

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“…Siegel and Haug (22) demonstrated that Al stoichiometrically denatured calmodulin and that Al reversed the calmodulinstimulated hyperpolarization of plasma membrane vesicles from barley roots. Suhayda et al (25) reported that Al inhibited proton transport by corn root plasma membrane vesicles. Several authors (7,22,24) have suggested that Al complexation with calmodulin represents a primary lesion that may lead to reduced membrane polarity and to other dysfunctions.…”

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confidence: 99%

Proton Extrusion by Wheat Roots Exhibiting Severe Aluminum Toxicity Symptoms

Kinraide

1988

Plant Physiol.

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ABSTRACIrThe mechanisms of Al rhizotoxicity are not known, but disruption of membrane function has been a persistent hypothesis. The objective of this study was to establish whether cells of Al-cultured wheat roots (Triticum aestivum L. cv Tyler) exhibiting severe Al toxicity symptoms were capable of vigorous proton extrusion. The membrane electrical potential difference (Em) was measured in individual cells throughout the first centimeter of root tips during perfusion with Al solutions similar to or more concentrated than those of the culture medium. For both Alcultured and control roots the resting Em was -100 millivolts, and 1 millimolar acetic acid induced cyanide-sensitive hyperpolarizations to -180 millivolts at a maximum rate of -30 millivolts per minute. Al, like Ca2", enhanced the negativity of the Em of cells already treated with acetic acid. Both acetic acid and fusicoccin stimulated net proton extrusion from Al-cultured and control roots, both of which also extruded protons in the absence of these stimulants. These results demonstrate that wheat roots exhibiting severe Al toxicity symptoms had an undiminished capacity to extrude protons, that the membranes were intact, and that ATP synthesis was sufficient to supply the proton-translocating ATPases.Al"3 is a rhizotoxic ion that is often present in acidic soils at activities sufficiently high to seriously inhibit root elongation (32). At least one unstable polynuclear hydroxy-Al species is even more toxic than Al3" (20), but its presence in soils has not been confirmed. The mononuclear hydroxy-Al species, which are in equilibrium with Al3", are probably nontoxic (20), and some other Al complexes are demonstrably nontoxic (3, 11, 24). Since no Al species of charge < +3 has been shown to be toxic, Al rhizotoxicity may simply be an instance ofthe apparently general rhizotoxicity of polyvalent cations (4,20).These considerations bear upon the unelucidated mechanisms of Al toxicity. It is unknown whether the primary lesion is intracellular or extracellular, but according to equilibrium computations the cytoplasmic levels of OH-and other ligands for Al would reduce A13+ to an extremely small fraction of the intracellular Al (14). An intracellular lesion is also hard to reconcile with the nontoxicity of AlSO4+ (11) and other species which would also quickly respeciate intracellularly and therefore be indistinguishable from Al3+. Perhaps the polyvalent cations are the only species of Al to enter the cell, but that contradicts the general principle that membranes are more permeable to ions of lower charge (18). Nevertheless, hypotheses for an intracellular lesion have been advanced (16,19,21), and the differences in varietal sensitivity to Al have been considered in terms of Al exclusion by plasma membranes (29) or intracellular detoxification by Al- binding organic ligands (1, 24).The alternative view-that the primary lesion is extracellular-is easier to reconcile with the general rhizotoxicity of polyvalent cations, some ofwhich are reportedly impermeant, at...

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“…3). This pH regulation of proton pump activity has also been demonstrated for corn root plasma membranes (25). In the corn membrane system the decrease in H+-pump activity associated with a change in pH from 7.0 to 5.5 was correlated with a decrease in membrane microviscosity.…”

Section: Aph and A# Development In Control And Salt-stressed Plasma Mmentioning

confidence: 66%

Electrostatic Changes in Lycopersicon esculentum Root Plasma Membrane Resulting from Salt Stress

et al. 1990

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Salinity-induced alterations in tomato (Lypersicon esculentum Mill. cv Heinz 1350) root plasma membrane properties were studied and characterized using a membrane vesicle system. ported by membrane-bound carriers at the expense of the electrochemical gradient (15). The biochemical properties (18) and the proton pump activity (26) of the plasma membranebound, ion-stimulated ATPase have been reported for a variety of plant species. These studies have focused mainly on the characterization of ATPase and proton pump activities on membrane fractions isolated from nonstressed tissues. The relationship between proton pump activity and cellular ion regulation is especially important in salt-stressed tissues. With this thought, we focused our investigation on salt-induced changes in plasma membrane function. Giannini et al. (10) describe a method for the isolation of plasma membrane-enriched vesicles that are transport competent and retain full activity for a prolonged time period when stored at -80°C. Using this plasma membrane vesicle system, we initiated a comparative study of proton transport, and membrane-bound ATPase activity in native vesicles isolated from control and salt-stressed tomato roots (Lycopersicon esculentum Mill. cv Heinz 1350). Characterization of salt stress effects on proton pump activity, ATPase kinetics, and the ion-stimulation of these processes provides essential information that is necessary to understand the role of the plasma membrane in the physiological mechanisms of salt tolerance. MATERIALS AND METHODS Plant MaterialTomato (Lypersicon esculentum Mill. cv Heinz 1350) seeds were germinated in vermiculite for 1 week and then were placed into aerated hydroponic solution culture (0.5x Hoagland solution [pH 6.0]) and maintained in a growth chamber. The plants were provided with 16 h daylight at a light intensity of 250 ,uE m-2 s-'. Day/night temperatures were maintained at 30°C/25°C. Salt stress was applied 10 d after transplanting at a rate of 0.1 MPa d-' (15 mm NaCl, 3 mM CaC12) for 4 consecutive days resulting in a 75 mm applied salt stress at a Na:Ca ratio of 5:1. The plants were 35-d-old at harvest. Plasma Membrane IsolationThe plasma membrane-enriched vesicle fractions that were used for ion transport measurements were isolated by the method of Giannini et al. (10); all solutions were kept at ice www.plantphysiol.org on May 12, 2018 -Published by Downloaded from

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pH‐related changes in maize root plasma membranes

Cited by 4 publications

References 15 publications

Effect of aluminium on membrane properties of soybean (Glycine max) cells in suspension culture

Effect of aluminium on membrane properties of soybean (Glycine max) cells in suspension culture

Proton Extrusion by Wheat Roots Exhibiting Severe Aluminum Toxicity Symptoms

Electrostatic Changes in Lycopersicon esculentum Root Plasma Membrane Resulting from Salt Stress

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