The Uptake of rubidium by the roots of some graminaceous and leguminous plants

Jackman, R. H.

doi:10.1080/00288233.1965.10423712

Cited by 22 publications

(10 citation statements)

References 16 publications

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“…Whereas K +, Rb+, and Cl-show the saturation kinetics of a single system at concentrations less than 1 mM (Elzam and Epstein 1965;Epstein, Rains, and Elzam 1965;Jackman 1965;Luttge and Laties 1966;Torii and Laties 1966), phosphate absorption is characterized by the operation of two separate systems of differing affinity. Certainly, one of these mechanisms, viz.…”

Section: Discussionmentioning

confidence: 99%

“…INTRODUOTION Examination of ion absorption by plant roots over a wide concentration range has demonstrated the existence of two different mechanisms for the absorption of a single ionic species (Epstein, Rains, and Elzam 1963;Elzam, Rains, and Epstein 1964;Jackman 1965;Epstein 1966). The absorption isotherm is characterized by a high affinity, low Km system (system 1) operative at concentrations below 1 IDM, and a low affinity, high Km system (system 2) operative at higher concentrations.…”

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confidence: 99%

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Phosphate Absorption and Long-Distance Transport in Wheat Seedlings

Edwards¹

1970

Aust. Jnl. Of Bio. Sci.

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SummaryThe absorption of phosphate by the roots and simultaneous transport to the tops of intact wheat seedlings has been studied over the concentration range 0·0001-50mM.In the low concentration range « 1 mM), phosphate absorption is characterized by the operation of two hyperbolic isotherms which represent sites of different affinity. Both sites may be located at the plasmalemma.. Alternatively, one site may be at the plasmalemma, with the other representing phosphate absorption by the microbial population on the root surface. Irrespective of location, it is postulated that both sites are involved in absorption of the predominant H2P04 ion species.At high concentrations (> 1 mM) a linear absorption isotherm is obtained. This result is consistent with the involvement of a passive absorption component across the plasmalemma.Long-distance transport of phosphate to the tops is described by a single hyperbolic isotherm at low concentrations, and a linear isotherm at high concentrations.The simultaneous absorption and transport studies establish beyond doubt, that the two low concentration mechanisms of phosphate absorption do not correspond to system 1 and system 2 of the dual absorption mechanism.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

Phosphate Absorption and Long-Distance Transport in Wheat Seedlings

Edwards¹

1970

Aust. Jnl. Of Bio. Sci.

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“…This increase in active transport is in the concentration range in which "mechanism 2" is commonly thought to operate. (Mung beans, like many other species, show a typical "mechanism 1" at much lower concentrations [20]. )…”

Section: Resultsmentioning

confidence: 99%

Chloride Accumulation by Mung Bean Root Tips

Gerson¹,

Poole²

1972

Plant Physiol.

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Net uptake of Cl-into root tips of mung bean (Phaseolus aureus) increases steadily with increasing external concentrations from 1 to 60 mM. Membrane potentials were measured to determine the equilibrium concentration of Cl-in the tissue which could be due to diffusion. This concentration was readily exceeded in both the relatively nonvacuolate tips (0 to 1 mm) and the vacuolate, mature upper sectons (1 to 11 mm) of the roots. The activity coefficient of both cytoplasmic and vacuolar Cl-, measured with Cl-sensitive microelectrodes, was approximately the same as that of a pure KCI solution of the same concentration. It is concluded that the "second mechanism" of ion uptake involves a large increase in the rate of active transport at the plasmalemma as the external concentration is increased above 1 mM. The additional influx has been ascribed to a second mechanism involving carrier sites at the membrane with very different properties from those of mechanism 1. This interpretation is supported by many detailed studies of the kinetics of isotope influx (12-14, 21, 29, 30, 34, 35). However, in the high concentration range it becomes difficult to apply the usual criteria for active transport, since the ion activities may approach thermodynamic equilibrium across the cell membrane (28), and since the influx rate is usually not described by simple Mi-chaelis-Menten kinetics (15,23). Indeed the influx often shows no sign of saturation at high concentrations and may be more suggestive of diffusion across the cell membrane (24,29,31 MATERIALS AND METHODSMung bean seeds (Phaseolus aureus) were sterilized in 0.5% sodium hypochlorite (v/v) for 15 min, washed for 10 min in running tap water, and then rinsed several times with distilled water. The seeds were planted on eight mesh stainless steel screens and covered with a single layer of cheesecloth. The screen was suspended over aerated 0.5 mm CaSO,, which was changed after the first 24 hr, and again several hours before an experiment. The seeds were constantly illuminated by a bank of four 40-w Sylvania GRO-LUX fluorescent bulbs located 30 cm above the plants. It should be noted that Ca2+ is necessary for healthy root growth: plants grown in distilled water produced roots with extremely flaccid tips. Experiments were performed on the tips (apical 1 mm) and upper sections (1-11 mm) of 3-to 5-day-old roots.All experimental solutions contained 0.5 mm CaSO, with the required concentration of KCl. Experiments were performed at 30 C; uptake solutions were aerated with filtered, water-saturated air at the same temperature. Net Cl-uptake was determined for the roots of intact plants. Transport of chloride to the rest of the plant did not affect our conclusions, since similar results were obtained with excised segments. To measure net uptake, the plants were transferred to stainless steel screens over 1-liter beakers containing the appropriate solutions; at the end of the uptake period segments were cut, washed in 0.5 mm CaSO4 for 15 min at 4 C, and weighed. Chloride was extr...

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“…There is a need, therefore, for long term studies with intact plants supplied with complete nutrient solutions for comparison with those of a short time period in simple salt solutions in the study of the kinetics of ion absorption (1,5). In the short time studies with either excised roots or intact plants it has been reported for simple salt solutions that K and Rb are mutually competitive on essentially equal terms, i.e., bound and transported by identical carrier sites (4,5). In the absorption of Na and K by excised barley roots, Rains and Epstein (8,9) postulated that a multiplicity of sites is concerned in transport of K and Na.…”

Section: Abstracrmentioning

confidence: 99%

“…Transport to and redistribution of minerals among the several organs of a plant, concurrent with growth and development, may significantly affect subsequent absorption of salts by roots from the multiple salt nutrient solutions. There is a need, therefore, for long term studies with intact plants supplied with complete nutrient solutions for comparison with those of a short time period in simple salt solutions in the study of the kinetics of ion absorption (1,5). In the short time studies with either excised roots or intact plants it has been reported for simple salt solutions that K and Rb are mutually competitive on essentially equal terms, i.e., bound and transported by identical carrier sites (4,5).…”

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confidence: 99%

Interaction of Rubidium or Sodium with Potassium in Absorption by Intact Sugar Beet Plants

El‐Sheikh¹,

Broyer²,

Ulrich³

1971

Plant Physiol.

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ABSTRACrThis study concerns the selective absorption of K and Rb or of K and Na by intact sugar beet (Beta vulgaris) plants from modified conventional nutrient solutions over an extended pe-riod of plant growth. Long term results agreed with those of short term experiments by other investigators nsing excised root systems and simple salt solutions. Potassium and Rb were mutually competitive in their absorption. High selectivity of K relative to Na absorption was observed. Sodium was excluded during the early growth period of sugar beets.Most of the information about ion absorption has been obtained with excised root systems over very short time periods and with single salt solutions (4, 7). Results with excised root systems may or may not be extended to those of intact plants grown in complex nutrient solutions. Transport to and redistribution of minerals among the several organs of a plant, concurrent with growth and development, may significantly affect subsequent absorption of salts by roots from the multiple salt nutrient solutions. There is a need, therefore, for long term studies with intact plants supplied with complete nutrient solutions for comparison with those of a short time period in simple salt solutions in the study of the kinetics of ion absorption (1,5). In the short time studies with either excised roots or intact plants it has been reported for simple salt solutions that K and Rb are mutually competitive on essentially equal terms, i.e., bound and transported by identical carrier sites (4,5). In the absorption of Na and K by excised barley roots, Rains and Epstein (8,9) postulated that a multiplicity of sites is concerned in transport of K and Na. In contrast, Jacobson et al. (7) postulated that there is a single common site for Na and K absorption.The present research concerns the influence of Na or Rb on K absorption from complex nutrient solutions. The rates of absorption of K as well as of the companion ions were determined from analyses of the culture solutions. Indirect evidence of carrier sites was observed. MATERIAIS AND MET'HODSBeta vulgaris seeds, variety M.S. NB1 X NB4, treated with Phygon-XL (2,3-dichloro-1,4-naphthoquinone) (6). These nutrients were added again to the old solutions in the same amounts, 20 and 36 days after transplanting. Two K concentrations were applied in each experiment, a low-K treatment (1 meq/liter) and a high-K treatment (8 meq/ liter). The low-K treatment allowed K deficiency symptoms to appear 3 to 4 weeks after transplanting while the high-K treatment supported favorable growth during a period of 42 days. The pH of the solutions was kept between 5.5 and 6.0 by the addition of 1.0 N H,SO, or 1.0 N NH,OH as necessary.Since the roots, especially the storage root, developed at different rates, solution volumes could not be practicably adjusted to the true initial volume, but were adjusted with distilled water to the initial pot level and sampled at 2-day intervals following transplantation. This deviation from the true volume does not affect the conclusi...

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The Uptake of rubidium by the roots of some graminaceous and leguminous plants

Cited by 22 publications

References 16 publications

Phosphate Absorption and Long-Distance Transport in Wheat Seedlings

Phosphate Absorption and Long-Distance Transport in Wheat Seedlings

Chloride Accumulation by Mung Bean Root Tips

Interaction of Rubidium or Sodium with Potassium in Absorption by Intact Sugar Beet Plants

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