Dual Mechanisms of Salt Uptake in Relation to Compartmentation and Long-Distance Transport

Laties, George G.

doi:10.1146/annurev.pp.20.060169.000513

Cited by 148 publications

(78 citation statements)

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“…Since high external ion concentrations were employed in these experiments, either the plasmalemma (36, 37) or tonoplast (22) would be strong candidates for the enzyme location, if indeed the ATPase is related to transport. Hall (12) has reported the existence of an ATPase on the plasmalemma of corn roots, and Poux (29) has shown that the tonoplast of small vacuoles and either the plasmalemma or cell walls of cucumber root cells contain ATPase activity.…”

Section: Discussionmentioning

confidence: 99%

Correlation between Ion Fluxes and Ion-stimulated Adenosine Triphosphatase Activity of Plant Roots

1970

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The energy-dependent influx of Rb+ into excised roots of corn, wheat, and barley has been determined and compared to the Rb+-stimulated ATPase activity of membrane fractions obtained from root homogenates of these species. The external Rb+ concentrations studied were in the range of 1 to 50 mM. (17,19,20) in roots, it would seem that ATP could also serve as the actual energy source for transport. In green algae it has been concluded that anion transport is more closely linked to the photosynthetic electron transport process whereas cation transport is coupled to ATP formation and utilization (25,30,31).In animal tissues it has been shown directly that ATP could provide the necessary energy for Na+ transport (5, 18). It has also been shown that an ATPase is intimately involved in this ATP-driven reaction (33). The existence of ion-sensitive ATPases in plant tissues has been reported recently for several plant species (2,4,6,8,11,13,15,21,26,32); however, none of these reports has shown the enzyme to have any relationship to ion transport. We (8) other plant species which possess different rates of ion transport, and the results provide correlative evidence for a role of the ATPase (and therefore ATP) in the energy-dependent transport of Rb+ and K+. MATERIALS AND METHODSPlant Culture. Roots from 4-day-old, dark-grown wheat (Triticum vulgare, 59 X 844), corn (Zea mays, WF9 X M14), and barley (Hordeum vulgare var. Arivat) were used. The seeds were placed between layers of cheesecloth on stainless steel screens 2 cm above a 0.2 mm CaSO4 solution with gentle aeration. All plants were kept at 25 2 C during the 4-day growing period.Influx Experiments. Rubidium influx was determined with 88Rb. Roots were excised and washed three times in approximately 250 ml of distilled water. The terminal 6 cm of five roots were cut into 1.5-cm segments and incubated in 50 ml of 0.5 mM CaSO4 plus the desired concentration of RbCl for 30 min. Solutions were maintained at 30 C during the absorption period and gentle aeration was provided. The experiments were terminated by rapid filtration on Buchner funnels. The root segments were rinsed for 30 sec with approximately 10 ml of an ice-cold washing solution (0.5 mm CaSO4-5 mm RbCl) and then placed into ice-cold washing solution for an additional 30 min. The roots were finally rinsed with the wash solution, placed in tared stainless steel planchets and weighed. Root tissue was ashed at 500 C for 1 hr and ash was moistened with 0.25 ml of 1% Photoflo, dried, and counted for radioactivity in a gas-flow counter.ATPase Experiments. The ATPase experiments were basically as described previously (8). Roots were excised and washed three times in approximately 250 ml of deionized water. The roots were chilled in cold deionized water for 15 min prior to grinding in a mortar and pestle with 100 ml of 0.25 M sucrose, 0.003 M EDTA, 0.01 M tris, pH 7.5. The tissue was ground vigorously for 45 sec, strained through four layers of cheesecloth, and finally diluted with 200 ml of 0.25 M sucrose. ...

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Section: Discussionmentioning

confidence: 99%

Correlation between Ion Fluxes and Ion-stimulated Adenosine Triphosphatase Activity of Plant Roots

1970

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“…The foregoing observations suggested more than a single carrier system for a given transportable species whether in parallel at the plasma membrane (27), or sequential, at plasma membrane and tonoplast, respectively (16). The recognition of the duality or multiplicity of the isotherms for ion absorption came with the examination of ion uptake in the external concentration range 0 to 0.1 mm, a range previously ignored in studies of salt uptake.…”

mentioning

confidence: 99%

Multiphasic Absorption of Glucose and 3-O-Methyl Glucose by Aged Potato Slices

Linask¹,

Laties²

1973

Plant Physiol.

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“…Both the root and the stem have been implicated in the regulation of Na transport to the leaves. Basically, the proposed mechanisms of root regulation involve discriminatory exclusion of Na at the plasmalemma (10,13,20), Na-selective absorption into the vacuole by the tonoplast (18) and possibly, active Na extrusion from the cortical cells across the plasmalemma (1 1, 18, 28, 29, 31). Further Na dilution may occur in the stem where Na is selectively withdrawn from the xylem stream by adjacent living cells (1,16,17,30,34,36) and either sequestered there or retranslocated by way of the phloem to the root (5,23).…”

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confidence: 99%

Radial Transport of Sodium and Chloride into Tomato Root Xylem

Maas

Ogata

1972

Plant Physiol.

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Transport of Na and Cl across exuding tomato (Lycopersicon esculentum Mill.) roots was determined as a function of ambient NaCl concentrations in the ranges of both systems 1 and 2.Kinetics of radial transport under steady-state conditions and the effect of dinitrophenol indicate that Na and Cl were transported by two (5,16,17,19,24,30,34,37). Both the root and the stem have been implicated in the regulation of Na transport to the leaves. Basically, the proposed mechanisms of root regulation involve discriminatory exclusion of Na at the plasmalemma (10, 13, 20), Na-selective absorption into the vacuole by the tonoplast (18) and possibly, active Na extrusion from the cortical cells across the plasmalemma (1 1, 18, 28, 29, 31). Further Na dilution may occur in the stem where Na is selectively withdrawn from the xylem stream by adjacent living cells (1,16,17,30,34,36) and either sequestered there or retranslocated by way of the phloem to the root (5,23).Directly related to the mechanism of exclusion, and perhaps differing only by degree, is the mechanism whereby accumulator plants translocate Na or Cl readily to the shoots. Recently, the concept of an active anion pump as the driving force for cation transport to the xylem has received increasing support (2-4, 12, 26, 27, 35). The rationale for this theory is based primarily on the interpretation of electrochemical potentials 64 measured across exuding roots. However, the interpretations are not unequivocally accepted (18,32,33), and the mechanism of Na and Cl transport to the xylem remains in doubt.The purpose of the present investigation was to test further the active anion pump concept of salt transport with a plant that readily transports Na and Cl to the shoot. The tomato plant was chosen because it meets this criterion and because the transport of Na by this plant has been reported to be metabolically facilitated (15). The role of metabolism and steady-state kinetics of radial transport were determined over a broad range of ambient NaCl concentrations. MATERIALS AND METHODSPlant Culture. Decapitated root systems from 23-day-old tomato (Lycopersicon esculentum Mill. cv. Heinz 1350) plants were used as the experimental material. Plants were grown from seed germinated between moist paper towels suspended over tenth-strength Hoagland's solution. Seedlings were transferred when 5 cm high to 14-liter polyethylene containers of half-strength Hoagland's solution. Phosphate was reduced to 0.25 mm and Fe was added as the metal chelate of diethylenetriamine pentaacetate. Culture solutions were prepared from demineralized water and reagent-grade salts. Eight plants per container were supported in holes in Styrofoam' covers with strips of polyurethane foam wrapped around the stem. The plants were grown in environmental chambers at 25 C and with a 16-hr photoperiod at 3300 ft-c light intensity. Solutions were aerated continuously and the pH was maintained between 6.0 and 6.5 with HNO.Experimental Procedure. All plants were transferred to 1 meq/1 CaSO4 solutions (pH 6) f...

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Dual Mechanisms of Salt Uptake in Relation to Compartmentation and Long-Distance Transport

Cited by 148 publications

References 1 publication

Correlation between Ion Fluxes and Ion-stimulated Adenosine Triphosphatase Activity of Plant Roots

Correlation between Ion Fluxes and Ion-stimulated Adenosine Triphosphatase Activity of Plant Roots

Multiphasic Absorption of Glucose and 3-O-Methyl Glucose by Aged Potato Slices

Radial Transport of Sodium and Chloride into Tomato Root Xylem

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