Oat Roots Research Articles

An Analysis of the Growth Inhibitory Characteristics of Alachlor and Metolachlor

The effects of varying concentrations and duration of alachlor [2-chloro-2′,6′diethyl-N-(methoxymethyl)acetanilide] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] treatment on root growth, cell division, and cell enlargement were studied. Peas (Pisum sativumL. ‘Alaska’) and oats (Avena sativaL. ‘Victory’) were treated from 0 to 48 h with concentrations ranging from 1 × 10-8to 1 × 10-3M of each herbicide. After 48 h, average growth rates were significantly inhibited at concentrations of 1 × 10-7M alachlor and 5 × 10−8M metolachlor, and 5 × 10−7M alachlor and 1 × 10-6M metolachlor for peas and oats, respectively. When growth inhibitions were examined across time at concentrations greater than these, the degree of growth inhibition was a function of both concentration and duration of treatment. Often the greatest decrease in growth occurred between 0 and 12 h. Mitotic indices of root tip squashes from pea roots and paraffin sections from oat roots were determined. There was a significant reduction in the mitotic indices of pea roots treated for 48 h with 5 × 10−6M alachlor or 1 × 10-5M metolachlor. After a 30-h treatment, the mitotic indices of oat roots were significantly reduced by 1 × 10−7M metolachlor and 1 × 10−6M alachlor. Significant inhibition of elongation of etiolated oat coleoptiles were observed at 5 × 10−6M alachlor (27%) and 5 × 10−5M metolachlor (30%). Inhibition of pea hypocotyl elongation did not occur at concentrations below 5 × 10−4M. It was concluded that the growth inhibition of plants caused by alachlor and metolachlor results from both an inhibition of cell division and cell enlargement.

The effects of rainfall and soil type on the population dynamics of cereal cyst nematode (Heterodera avenae) on spring barley (Hordeum vulgare) and spring oats (Avena sativa)

SUMMARYIn experiments applying water regimes ranging from one eighth to twice the recorded average rainfall to six soils (two light sands and four silty clay loams) consistent positive correlations were found between rainfall and (a) the growth of foliage and roots of spring barley and spring oats, (b) the number of larvae which invaded the root system, (c) the number of immature females in July, and (d) the incidence of the fungus Verticillium chlamydosporium, an egg parasite of H. avenae. Final cyst numbers were sometimes lower than the number of immature females, probably because the latter were destroyed by the ‘Entomophthora‐like’ fungus (Kerry & Crump 1977). Final populations of cysts and eggs were not always proportional to the number of larvae in root systems (even when the proportion of males was constant) but appeared more likely to be so in light sandy soils.

Relationship between pre-formed inhibitors in oats and infection by Gaeumannomyces graminis and Phialophora radicicola

Growth by varieties of Gaeumannomyces graminis and Phialophora radicicola, and Leptosphaeria narmari (LN), was studied on oat and wheat seedlings and on water-extracts of oats and wheat. All fungi grew less well on oat than on wheat roots, though the degree of growthreduction varied: P. radicicola var. graminicola (PRG) was generally least affected by hosttype and P. radicicola var. radicicola (PRR, lobed hyphopodia) was most affected, though isolates within these taxa differed, one from another. For all fungi, the most pronounced difference on oat and wheat roots was in density rather than extent of runner-hyphae from the inoculum. On coleoptiles, G. graminis var. graminis (GGG) grew equally well on oats and wheat, whereas growth by PRR was markedly reduced on oats. The differences in behaviour on seedlings were paralleled by differences on oat and wheat extracts. G. graminis var. tritici (GGT) and PRR were strongly inhibited by oat root or shoot extracts; G. graminis var. avenae (GGA) and some isolates of PRG were inhibited by oat shoot but not oat root extract, and GGG, LN and most isolates of PRG grew well on root and shoot extracts of oats. Within this last group, PRG and LN detoxified oat shoot extract and enabled growth by GGT, whereas GGG did not do so. The results support and extend Turner's (1961) hypothesis, that pre-formed inhibitors in oat sap are implicated in host-resistance; they also suggest that oats might be used to alter the population balance between GGT and similar fungi, which act as biological control agents.

Factors related to iron uptake by dicotyledonous and monocotyledonous plants III. Competition between root and external factors for Fe

Abstract In comparison studies (11, 12), monocotyledonous corn (Zea mays L.) and oats (Avena byzantina C. Koch) did not respond to Fe stress as effectively nor to the same degree as the dicotyledonous soybeans (Glycine max (L.) Merr.) or tomatoes (Lycopersicon esculentum Mill.). Both the Fe‐inefficient and Fe‐efficient corn and oats developed Fe chlorosis; the Fe‐efficient dicotyledonous plants were green. In the present study, the method of inducing Fe stress was changed to make it less severe. Instead of using only NO3‐N and no Fe to induce Fe stress (11, 12), both NH4‐N and NO3‐N were used along with varied concentrations of Fe. Iron stress was induced with BPDS (4,7‐diphenyl‐l, 10‐phenan‐throline disulfonic acid) and phosphate; both competed with the plant for Fe. Phosphate also inhibits reduction of Fe3+ to Fe2+ (12). This method of inducing Fe stress in the plants was less severe than using only NO3‐N and no Fe in the nutrient solutions and we were able to measure a difference in Fe‐stress response for all four plant species (Fe‐inefficient and Fe‐efficient). At the lower Fe treatments, the roots of Fe‐efficient plants usually reduced more Fe3+ to Fe2+ than did the roots of Fe‐inefficient plants. The ‘inefficient’ ys1 corn and TAM 0–312 oat roots did not compete with BPDS or phosphate for Fe as effectively as did the ‘efficient’ WF9 corn and Coker 227 oat roots. The same type mechanism for solubilization, absorption, and transport of Fe seems to function in both monocotyledenous and dicotyledenous plants but it is more effective and more readily detected in the dicot than in the monocot plants. The reactions involved in reduction of Fe3+ to Fe2+ seemed to be confined inside or at the root surface for the inefficient genotypes; the efficient genotypes alter the ambient medium to a greater degree.

Inhibition of Adenosine Triphosphatase Activity of the Plasma Membrane Fraction of Oat Roots by Diethylstilbestrol

Diethylstibestrol (DES) inhibited noncompetitively the ATPase in the plasma membrane fraction from Avena sativa L. cv. Goodfield roots when assayed in the presence of MgSO(4) or MgSO(4) plus KCl. In the presence of MgSO(4), 7.1x10(-5) molar DES inhibited the enzyme 50%; whereas in the presence of MgSO(4) and KCl, 1.3x10(-4) molar DES was required for the same inhibition. Dixon plots indicated that in the presence of MgSO(4), one molecule of DES bound to one molecule of ATPase; however, in the presence of MgSO(4) and KCl, two or more molecules bound to one ATPase molecule. These results suggested that KCl causes a conformational change in the enzyme which exposes additional binding sites for DES, but that these sites are not as inhibitory as the first binding site.In addition to KCl, other factors also affected the DES inhibition of the ATPase. Plasma membrane vesicles warmed to 38 C were inhibited more than vesicles kept on ice prior to assay. DES inhibited the Triton X-100-treated ATPase less than the ATPase which was not detergent-treated. Finally, studies with DES analogs showed that the hydroxyl groups of DES were essential for inhibition and that steric configurations of the molecule were important.DES inhibition of the ATPase suggests that DES inhibits K(+) absorption in oat roots by inhibiting the ATPase. Inhibition of K(+) absorption was greater than inhibition of the ATPase, and thus DES may also inhibit other aspects of metabolism that are involved with ion absorption.

Comparison of Reductions in Adenosine Triphosphate Content, Plasma Membrane-associated Adenosine Triphosphatase Activity, and Potassium Absorption in Oat Roots by Diethylstilbestrol

The possibility was investigated that diethylstilbestrol (DES) inhibits potassium absorption in oat (Avena sativa L. cv. Goodfield) roots by inhibiting mitochondrial functions in addition to inhibiting the plasma membrane ATPase. DES at 10(-6) molar stimulated the mitochondrial ATPase slightly, but higher concentrations had no effect. Oxidative phosphorylation by isolated mitochondria was inhibited 50% by 2.6 x 10(-5) molar DES; concentrations of 10(-4) molar or greater were completely inhibitory. After a lag of about 2 minutes, 10(-4) molar DES produced a linear decrease in ATP content of excised roots. After 20 minutes, the ATP content of the tissue was about 50% of the control and remained at that level after 30 minutes in DES.Comparison of changes in ATP content, plasma membrane ATPase activity, and K(+) absorption rate with time in the presence of DES showed that the rapid decrease in K(+) absorption rate corresponded more closely with the decrease in ATPase activity than the decrease in ATP content. Total inhibition of the ATPase was calculated by multiplying together the percentage decreases in ATPase activity and ATP content. At times greater than 10 minutes this "net" ATPase activity corresponded very closely with the K(+) absorption rate.These results show that DES can inhibit potassium absorption by reducing mitochondrial ATP production in addition to inhibiting the plasma membrane ATPase. However, the rapid (less than 5 minutes) inhibition of absorption is caused by direct inhibition of the ATPase rather than a reduced ATP supply because the ATP content is lowered only slightly whereas the ATPase is inhibited dramatically in that time. The relationship between plasma membrane ATPase activity and K(+) absorption rate as inhibited by DES supports the hypothesis that the ATPase is involved in cation absorption by plant roots.

Effect of Diethylstilbestrol on Ion Fluxes in Oat Roots

Effects of diethylstilbestrol (DES) on ion fluxes in oat roots (Avena sativa L.) were investigated by measuring K(+) and Cl(-) absorption and K(+) efflux. DES rapidly decreased the absorption of K(+) ((86)Rb) and (36)Cl(-) by excised roots; 10(-4) molar DES inhibited Cl(-) absorption in 1 minute and K(+) absorption in 1 to 2 minutes. With a 10-minute incubation period, K(+) and Cl(-) absorption were inhibited 50% by 1.1x10(-5) molar and 8.4x10(-6) molar DES, respectively. Treatment for 3 minutes with 10(-4) molar DES caused irreversible inhibition of K(+) absorption. Increasing concentrations of KCl in the absorption media decreased the DES inhibition. Experiments with the DES analogs, DES dipropionate, dienestrol and hexestrol, showed that the steric configuration and the hydroxyl group of the DES molecule are important in determining the inhibitory capacity of the compound.DES increased the efflux of (86)Rb from excised roots only after a 10-minute lag period. In 10(-4) molar DES, roots lost 82% of their radionuclide content in 1 hour. Comparison of efflux curves for roots loaded for 20 hours and those loaded for 15 minutes suggested that DES increased the permeability of the plasma membrane after about 10 minutes and the permeability of the tonoplast after 10 to 20 minutes. Oligomycin and dinitrophenol also increased the loss of (86)Rb, but the lag period was about 4 hours.The rapid effect of DES on ion absorption and the slower effect on ion efflux suggest that DES initially inhibits ion uptake by affecting the transport mechanism at the plasma membrane in some manner other than alteration of membrane permeability.

Temperature Effect of Phytotoxicity of Soil-Applied Herbicides

Experiments were conducted in controlled environmental chambers to determine the influence of temperature on the phytotoxicity of seven soil-applied herbicides. Diclofop {2-[4-(2,4-dichlorophenoxy)phenoxy] propanoic acid} soil incorporated or surface applied, was more toxic to wild oat(Avena fatuaL.) shoots at 10 and 17 C than at 24 C. Efficacy of diclofop was enhanced with soil incorporation. Diclofop toxicity to wild oat roots was not influenced by a change in temperature. EPTC(S-ethyl dipropylthiocarbamate) stimulated sugarbeet(Beta vulgarisL. ‘American Crystal Hybrid B’) shoot dry weight production at 10 C and caused dry weight reduction at 24 C. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] toxicity to barley(Hordeum vulgareL. ‘Larker’) and alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] toxicity to oats(Avena sativaL. ‘Chief’) increased with increased temperature from 10 to 17 C. Temperatures within the range of 10 to 24 C did not affect trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) toxicity to barley or BAY-5653 [N-(2-benzothiazolyl)-N-methylurea] or chloamben (3-amino-2,5-dichlorobenzoic acid) toxicity to oats.

Cadmium Alteration of Root Physiology and Potassium Ion Fluxes

Segments of oat (Avena sativa L.) roots which had been exposed to 1 millimolar CdSO(4) in quarter-strength Hoagland No. 1 solution exhibited decreased respiratory rates, ATP levels, membrane-bound ATPase activity, and reduced K(+) fluxes. Respiration and ATP levels were decreased after a 2-hour treatment with 1 millimolar CdSO(4) to 65 and 75%, respectively, of control rates. A membrane-bound, Mg(2+)-dependent, K(+)-stimulated acid ATPase was rapidly inhibited to 12% of control activity in the presence of 1 millimolar CdSO(4). Potassium uptake into root segments was inhibited to 80% of control values after 30 minutes in the presence of CdSO(4). A 2-hour pretreatment of root segments with CdSO(4) inhibited K(+) uptake to 15% of control values. Cytoplasmic K(+) efflux was inhibited with 1 millimolar CdSO(4).The rates and the degree of Cd(2+) inhibition of the parameters listed above suggest that one of the first sites of Cd(2+) action is the plasmalemma K(+) carrier (ATPase) in oat roots.

Selectivity and Site of Action in Relation to Field Performance of Diclofop

In the greenhouse, the methyl ester of diclofop {2-[4-(2,4-diclorophenoxy)phenoxy] propanoic acid} as a postemergence application at 1.1 kg/ha ai did not affect the growth of the seven dicotyledonous crops with the exception of slight injury to yellow [white] mustard(Brassica hirtaMoench). Of the 13 gramineous species, corn(Zea maysL.), green foxtail [Setaria viridis(L.) Beauv.], oats(Avena sativaL.) wild oats(Avena fatuaL.), sorghum [Sorghum bicolor(L.) Moench], and timothy(Phleum pratenseL.) were rated highly susceptible, while barley(Hordeum vulgareL.), bromegrass [smooth brome](Bromus inermisLeyss.), durum wheat(Triticum durumDesf.), intermediate wheatgrass [Agropyron intermedium(Host) Beauv.], Russian wild ryegrass(Elymus junceusFisch.), triticale(X TriticosecaleWittmack), and wheat(Triticum aestivumL.) were relatively tolerant. Residue of diclofop in the soil partially controlled green foxtail which was seeded 3 weeks after herbicide application. Whether applied to wild oat shoots or roots, diclofop affected the entire plant, but growth reduction was great when applied to the shoots. Field results confirmed that foliar application gave the best weed control resulting in larger wheat yield increases. Wild oat control was greatly enhanced when an adjuvant was added to diclofop. This enhanced herbicidal activity appeared to have no effect on tolerance of barley at 0.8 kg/ha nor wheat at 1.1 kg/ha. Increasing the temperature from 12 to 28 C decreased wild oat control from diclofop at 1.1 kg/ha. In the field, diclofop at rates ranging from 0.8 to 2.2 kg/ha gave good control of wild oats and green foxtail resulting in significantly increased wheat yield compared to the checks. However, barley yield increases were obtained only at the rates from 0.8 to 1.1 kg/ha, indicating that at the higher rates barley was less tolerant than wheat. The 0.6 kg/ha rate with an adjuvant gave adequate weed control and significant barley yield increases over the checks, when evaluated on five barley cultivars.

Alkylguanidine Inhibition of Ion Absorption in Oat Roots

The effect of various alkylguanidines on ion absorption and energy metabolism in oat (Avena sativa cv. Goodfield) roots has been investigated. Of several alkylguanidines tested, octylguanidine was the most effective inhibitor of both K(+) and Cl(-) absorption by excised roots. At 225 mum octylguanidine, the transport of both ions was inhibited within 60 seconds and to a similar extent. Octylguanidine inhibited mitochondrial oxidative phosphorylation and mitochondrial adenosine 5'-triphosphatase (ATPase). The plasma membrane ATPase was also inhibited if the membranes were diluted and pretreated with Triton X-100.Concentrations of octylguanidine giving half-maximal inhibition of K(+) influx, mitochondrial ATPase, oxidative phosphorylation, and plasma membrane ATPase were 50, 50, 100, and 275 mum, respectively. With increasing chain length, alkylguanidines (225 mum) became progressively more inhibitory to K(+) absorption and to the mitochondrial ATPase. Shorter chain guanidines slightly inhibited the plasma membrane ATPase, however, these compounds produced a slight stimulation in oxidative phosphorylation.Conditions of Triton treatment that were important in the elimination of permeability barriers of plasma membrane vesicles to ATP, Mg(2+), KCl, and octylguanidine were: concentration of Triton during pretreatment and in the assay media, concentrations of sucrose and plasma membrane during Triton treatment, and temperature of Triton treatment.Inhibition by octylguanidine of K(+) and Cl(-) absorption by excised oat roots may be due to an inhibition of either the plasma membrane ATPase or mitochondrial oxidative phosphorylation. The isolated plasma membrane did not appear to be permeable to octylguanidine since the plasma membrane ATPase was inhibited only after treating the membrane with Triton. This result indicates that the primary site of action of octylguanidine in excised root is more likely to be the plasma membrane ATPase than mitochondrial oxidative phosphorylation.

Inhibition of ion absorption in oat roots: comparison of diethylstilbestrol and oligomycin

The effects of diethylstilbestrol (DES) and oligomycin, inhibitors of ion absorption in animal cells, on the energetics of ion absorption in oat roots were compared. Both compounds inhibited K + and Cl − absorption in excised roots and oxidative phosphorylation in isolated mitochondria. DES inhibited a plasma membrane ATPase that is involved with ion absorption but did not inhibit the mitochondrial ATPase, whereas, oligomycin inhibited the mitochondrial ATPase but inhibited the plasma membrane ATPase only slightly. These results show that both compounds inhibit ion absorption by affecting ATP metabolism. Decreases in ATP production (oxidative phosphorylation) and ATP utilization (plasma membrane ATPase) account for the inhibition by DES. However, oligomycin does not affect the plasma membrane ATPase, and thus the mechanism of action of oligomycin is probably restricted to inhibition of ATP production. This is the first report that DES inhibits ion absorption in plant cell. The compound appears to inhibits ion absorption in oat roots by the same mechanism as in animal cells.

Selectivity of Alkali Cation Influx Across the Plasma Membrane of Oat Roots

Influx of alkali cations (Li(+), Na(+), K(+), Rb(+), Cs(+)) across plasma membranes of cells of excised roots of Avena sativa cv. Goodfield was selective, but different, in the absence and in the presence of 1 mm CaSO(4). Ca(2+) reduced the influx rates of all of the alkali cations-especially Na(+) and Li(+). Transport selectivity changed as the external concentrations of the alkali cations increased.Plasma membrane ATPase, purified from Avena sativa roots, was differentially stimulated by alkali cations. This specificity, however, was not altered by Ca(2+) or the external cation concentrations. A close correspondence existed between the relative influx rates of K(+), Rb(+), and Cs(+) and the relative stimulation of the ATPase by these cations. A similar correspondence did not occur for Na(+) and Li(+).Selective cation transport in oat roots could result, in part, from the specificity of the plasma membrane ATPase, but other factors such as specific carriers or porters or differential diffusion rates must also be involved.

Organic matter transformations in soils

Post-incubation fractionation of soils incubated with C14-tagged oat roots under aerobic and anaerobic conditions and chromatographic separation of hydrolysates of different organic matter fractions indicated the incorporation of C14-labelled amino acids in soil organic matter. Anaerobic incubation leads to the formation of hydrolysable heavily C14-labelled organic substances in greater quantity. The amino acid composition of the different fractions revealed not a very significant qualitative difference. The significance and causes of stabilization of amino acids in soil organic matter are discussed.

Isolation and Identification of the Precursor of Ethane in Phaseolus vulgaris L

Ethane production by homogenates of Phaseolus vulgaris L. cv. Harvester was studied. The precursor of ethane was identified as linolenic acid. The liberation of ethane was optimum at pH 4.2 and was highest from homogenates of leaves and apical buds. When roots were homogenized in linolenic acid solution, ethane and ethylene production were stimulated. In corn root homogenates, ethylene biosynthesis was stimulated nearly 8-fold by linolenic acid. The enzyme responsible for ethane production from oat root homogenates was soluble and had a high molecular weight.

Asulam mixtures for weed control in flax

Summary:Five field experiments were conducted from 1972 to 1975 to evaluate weed control in flax (Linum usitatissimum L.) using post‐emergence treatments of asulam [methyl (4‐aminobenzenesulphonyl) carbamatel alone and in combination with other herbicides. The 14C‐asulam absorption by leaf segments and roots of glasshouse grown wild oats (Avena fatua L.) was also investigated. Asulam at 1.12 kg/ha gave good wild oat control and acceptable control of green foxtail (Setaria viridis (L.) Beauv.). However, wild oat control was poorer when asulam was combined with other herbicides: on a 3‐year average, as compared with asulam alone at equal rates, the asulam+MCPA mixture resulted in a greater antagonism and a significant 6% reduction in flax seed yield, whereas the asulam+bromoxynil/MCPA mixture gave the least antagonistic effect, improved broadleaf weed control and increased yield by 13%. In mixtures, the potassium salt of MCPA was more compatible with asulam for weed control than the amine form. Both leaf segments and roots of wild oats absorbed and distributed less 14C‐asulam from solutions containing MCPA than from those containing bromoxynil or bromoxynil/MCPA.

The Effect of some Flavonoids on the Protoplasmic Streaming in Oat (Avena sativa) Root Hairs

Summary We have investigated the effect of three flavonol aglycones (kaempferol, quercetin and myricetin) and their glycosides (robinin, rutin and myricitrin, respectively), in concentration of 5.10 -5 and 5.10 -6 M, on protoplasmic streaming within oat root hairs. It was found that the aglycones at 5.10-5 M had an inhibitory effect on rotational streaming. This action could be explained by a flavonol-induced inhibition of some reaction leading to the formation of ATP - the energy source for the streaming. This action is transient. The protoplasmic streaming is restored after the removal of the flavonol aglycones. At 5.10 -6 M the rotational streaming was stimulated, indicating a possible promotion of the energy-producing reactions the cell. The glycosides in both concentrations increased the rate of the streaming. The effect given by each of the flavonol aglycones is specific, and this is discussed as related to their molecular structure. Quercetin proved to be the most active, followed by kaempferol and myricetin. The difference among these compounds lies in the hydroxylation pattern of the B ring, showing that the number and position of the OH groups alters the physiological effect of these flavonoids.

Temperature Response and Effect of Ca2+ and Mg2+ on ATPases from Roots of Oats and Wheat as Influenced by Growth Temperature and Nutritional Status

AbstractActivation by Ca2+, Mg2+, Zn2+, or Mn2+ of adenosine triphosphatases in a microsomal fraction from wheat roots depends upon the growth temperature when the plants are grown under low salt conditions, but not when the plants get a full‐strength culture medium. At low ionic strength, cultivation at 25°C gives only half as high activation as cultivation at 18°C or at high ionic strength at both temperatures.Corresponding data for activation of ATPases from oats also show that low ionic strength during growth gives the highest temperature dependence. Low temperature together with low salt conditions during growth gives the highest ATPase activity after stimulation with divalent cations. High growth temperature and full‐strength medium decrease the ATPase activity.Activation energies (Ea) were calculated for the two temperature intervals 35–20°C and 20–5°C. The dominating ATPase stimulation (Ca2+ in wheat, Mg2+ in oats) is characterized by high specific activity combined with a low Ea value.The differences in ATPase activity between oats and wheat can be correlated with different cultivation requirements known from agriculture.

Characterization of Passive Ion Transport in Plasma Membrane Vesicles of Oat Roots

The passive influx and efflux of inorganic ions across plasma membrane vesicles purified from extracts of Avena sativa roots were investigated. Uptake was measured by incubating the vesicles in a radioisotope for various times. The "loaded" vesicles were separated from the external solution by gel filtration. Efflux was measured by dialyzing the preloaded vesicles.Ion transport was differentiated from superficial ion binding by (a) the time course of association of radioisotope with the vesicles; (b) the rate of loss of radioisotope from the vesicles; (c) the linear increase in isotope associated with the vesicles as the external concentration was increased; (d) the enhanced loss of radioisotope from the vesicles induced by Triton X-100; and (e) the low amount of isotope associated with the vesicles at low temperatures.The plasma membrane vesicles were differentially permeable to the alkali cations with the order of decreasing permeation being K(+) > Rb(+) > Cs(+) > Na(+) > Li(+). The relative transport of Rb(+), Na(+), and Cl(-) across the plasma membrane vesicles was about 1.0:0.50:0.18. The permeability coefficient (P) for Rb(+) was estimated to be 0.29 +/- 0.15 x 10(-8) cm/sec.ATP (and ADP) decreased the passive uptake of Rb(+) into the vesicles, however, this effect did not appear to be related to the ATPase of the plasma membrane.

The use of labelled cations to measure victorin-induced permeability changes

We have described a technique for using labelled cations to measure the induction of electrolyte leakage in victorin-sensitive oat root cells caused by the host-specific toxin, victorin. The technique provides a rapid and sensitive way to measure leakage of specific labelled ions. By using the technique, we have demonstrated that the 86Rb leakage follows the same pattern as electrolyte leakage, in general, after victorin treatments. CaCl2 at 50 mM concentrations inhibits victorin activity as measured by 86Rb leakage. 45Ca retention is not affected by victorin the same as 86Rb or electrolytes in general. Some possible implications of the differential effects of victorin on45Ca and 86Rb in relation to the calcium's role in membrane function are discussed.