Sulfate Transport in Cultured Tobacco Cells

SUMMARYMycorrhizas have been shown to alter ion fluxes for many nutrients. Experiments were done to determine the extent to which ectomycorrhizas alter the ionic balance of roots of Douglas-fir {Pseudotsuga menziesii (Mirb.) Franco) seedlings mycorrhizal with Hebeloma crustuliniforme (Bull, ex St. Amans) Qiiel. exposed to solutions containing either '^N ammonium sulphate or *N ammonium chloride. Net fluxes of ammonium, hydrogen, potassium, calcium, sodium, bicarbonate, sulphate and chloride were measured. The mycorrhizal association altered ion fluxes, primarily decreasing sodium uptake and potassium release rates (both anion treatments) and increasing bicarbonate release during exposure to ammonium chloride. Rates of carboxylate accumulation in the tissue were inferred from the net flux data; mycorrhizal seedlings may produce more cation-carboxylate complexes compared with nonmycorrhizal seedlings. When compared with agricultural plants exposed to ammonium, Douglas-fir took up a considerably greater number of cations for each ammonium ion absorbed, which may account for the greater number of carboxylate anions also produced by Douglas-fir. These findings were discussed in terms of ecological significance for growth of Douglas-fir.

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“…solution (Jones & Smith, 1981). Our rates were only about 01 /«eq g d.wt"' h~\ suggesting little or no SO^^" net flux.…”

Section: -mentioning

confidence: 62%

Ectomycorrhizas Affect Ionic Balance During Ammonium Uptake by Douglas‐fir Roots

Bledsoe

Rygiewicz

1986

New Phytologist

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“…A particularly thorough analysis of the transporter system from Penicillium, performed by Cuppoletti and Segel (1975), indicated the presence of proton/sulphate/calcium cotransport. No evidence for a transport coupled with calcium has been found for higher plants (Skjelbreid and Nissen 1980;Jones and Smith 1981).…”

Section: Introductionmentioning

confidence: 90%

Sulphate/proton cotransport in plasma-membrane vesicles isolated from roots of Brassica napus L.: increased transport in membranes isolated from sulphur-starved plants

Hawkesford

Davidian

Grignon

1993

Planta

114

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Abstract. The characteristics of sulphate uptake into right-side-out plasma-membrane vesicles isolated from roots of Brassica napus L., Metzger, cv. Drakkar, and purified by aqueous polymer two-phase partitioning, were investigated. Sulphate uptake into the vesicles was driven by an artificially imposed pH gradient (acid outside), and could be observed for 5-10 min before a plateau was reached and no further net uptake occurred. The uptake was partially inhibited in the presence of depolarizing agents and little uptake was observed in the absence of an imposed pH gradient. Uptake was strongly pH-dependent, being greatest at more acidic pH. After imposition of a pH gradient, the capacity for uptake decreased slowly (tl/2 > 10 min). The uptake had a highaffinity component which was strongly dependent on the external proton concentration (Km= 10 laM at pH 5.0, 64 oM at pH 6.5). The K m for protons varied from 0.4-1.9 IJM as the sulphate concentration was reduced from 33 to 1 laM. A low-affinity component was observed which could be resolved at low temperatures (0 ~ Microsomal membranes that partitioned into the lower phase of the two-phase system gave no indication of high-affinity sulphate transport. Sulphate uptake into plasma-membrane vesicles isolated from sulphur-starved plant material was approximately twofold greater than that observed in those isolated from sulphate-fed plant material. Isolated vesicles therefore mirror the wellknown in-vivo response of roots, indicating an increase in the number of transporters to be, at least in part, the underlying cause of derepression.

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“…The number of phases, as well as K m and V max values were dependent on plant species and varieties (e.g. Jones and Smith 1981;Rennenberg et al 1988). Beech trees showed triphasic sulfate uptake kinetics (Kreuzwieser et al 1996), but oak trees only one phase (Seegmüller et al 1996).…”

Section: Characteristics Of Sulfate Uptake and Xylem Loadingmentioning

confidence: 97%

Regulation of sulfate uptake and xylem loading of poplar roots (Populus tremula x P. alba)

Zalm

Schneider

Rennenberg

2004

Trees

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Sulfate transport processes and its regulation were studied in roots of poplar trees (Populus tremula x P. alba). From the exponential increase in sulfate uptake with temperature an activation energy (E a ) of 9.0±0.8 kJ mol −1 was calculated. In the concentration range 0.005-10 mM sulfate uptake showed biphasic Michaelis-Menten kinetics with a K m of 3.2±3.4 μM and a V max of 49±11 nmol SO 4 2− g −1 FW h −1 for the high-affinity uptake system (phase 1) and a K m of 1.33±0.41 mM and a V max of 255±25 nmol SO 4 2− g −1 FW h −1 for the low-affinity system (phase 2). Xylem loading decreased linearly with temperature and remained unchanged within the sulfate concentration range studied. Regulation of sulfate uptake and xylem loading by O-acetyl serine (OAS), Cys, reduced glutathione (GSH), Met and S-methylmethionine (SMM) were tested by perfusion into the xylem sap with the pressure probe and by addition to the incubation medium. When added directly to the transport medium, Cys and GSH repressed, and OAS stimulated sulfate uptake; xylem loading was stimulated by Cys, repressed by GSH and only slightly affected by OAS. When perfused into the xylem, none of the compounds tested affected sulfate uptake of excised roots, but xylem loading was stimulated by SMM and OAS and repressed by Met. Apparently, the site of application strongly determined the effect of regulatory compounds of sulfate transport processes.

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Sulfate Transport in Cultured Tobacco Cells

Cited by 24 publications

References 10 publications

Ectomycorrhizas Affect Ionic Balance During Ammonium Uptake by Douglas‐fir Roots

Ectomycorrhizas Affect Ionic Balance During Ammonium Uptake by Douglas‐fir Roots

Sulphate/proton cotransport in plasma-membrane vesicles isolated from roots of Brassica napus L.: increased transport in membranes isolated from sulphur-starved plants

Regulation of sulfate uptake and xylem loading of poplar roots (Populus tremula x P. alba)

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