Accumulation of Potassium, Cesium, and Rubidium in Bean Plants Grown in Nutrient Solutions

Cline, J.F.; Hungate, F.P.

doi:10.1104/pp.35.6.826

Cited by 90 publications

(35 citation statements)

References 7 publications

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“…There is no known role for Cs + in plant nutrition (Bowen, 1979 ;Marschner, 1995 (Cline & Hungate, 1960 ;Kordan, 1987). The transport of monovalent cations across the root to the xylem occurs mainly through the root symplast (Marschner, 1995), and Cs + must cross the plasma membrane of root cells at least twice before it can be transported to the shoot.…”

Section: :    mentioning

confidence: 99%

Tansley Review No. 113

White¹,

Broadley²

2000

New Phytologist

315

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Caesium (Cs) is a Group I alkali metal with chemical properties similar to potassium (K). It is present in solution as the monovalent cation Cs + . Concentrations of the stable caesium isotope "$$Cs in soils occur up to 25 µg g −" dry soil. This corresponds to low micromolar Cs + concentrations in soil solutions. There is no known role for Cs in plant nutrition, but excessive Cs can be toxic to plants. Studies of the mechanism of Cs + uptake are important for understanding the implications arising from releases of radioisotopes of Cs, which are produced in nuclear reactors and thermonuclear explosions. Two radioisotopes of Cs ("$%Cs and "$(Cs) are of environmental concern owing to their relatively long half-lives, emissions of β and γ radiation during decay and rapid incorporation into biological systems. The soil concentrations of these radioisotopes are six orders of magnitude lower than those of "$$Cs. Early physiological studies demonstrated that K + and Cs + competed for influx to excised roots, suggesting that the influx of these cations to root cells is mediated by the same molecular mechanism(s). The molecular identity and\or electrophysiological signature of many K + transporters expressed in the plasma membrane of root cells have been described. The inward-rectifying K + (KIR), outward-rectifying K + (KOR) and voltage-insensitive cation (VIC) channels are all permeable to Cs + and, by analogy with their bacterial counterparts, it is likely that ' high-affinity ' K + \H + symporters (tentatively ascribed here to KUP genes) also transport Cs + . By modelling cation fluxes through these transporters into a stereotypical root cell, it can be predicted that VIC channels mediate most (30-90%) of the Cs + influx under physiological conditions and that the KUP transporters mediate the bulk of the remainder. Cation influx through KIR channels is likely to be blocked by extracellular Cs + under typical ionic conditions in the soil. Further simulations suggest that the combined Cs +

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Section: :    mentioning

confidence: 99%

Tansley Review No. 113

White¹,

Broadley²

2000

New Phytologist

315

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“…Excessive Cs 1 in the rhizosphere could, therefore, induce K starvation in plants. The growth of a number of plant species, including bean, tomato, Arabidopsis, and rice, is inhibited by Cs 1 concentrations in the rhizosphere exceeding 200 mM (Cline and Hungate, 1960;Kordan, 1987;Sheahan et al, 1993;Hasegawa, 1996;White and Broadley, 2000). The symptoms of Cs intoxication can be reversed, however, by supplying more K. This is consistent with the hypothesis that Cs is toxic because it interferes with K uptake and/or K biochemistry.…”

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confidence: 99%

Cesium Toxicity in Arabidopsis

et al. 2004

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Cesium (Cs) is chemically similar to potassium (K). However, although K is an essential element, Cs is toxic to plants. Two contrasting hypotheses to explain Cs toxicity have been proposed: (1) extracellular Cs+ prevents K+ uptake and, thereby, induces K starvation; and (2) intracellular Cs+ interacts with vital K+-binding sites in proteins, either competitively or noncompetitively, impairing their activities. We tested these hypotheses with Arabidopsis (Arabidopsis thaliana). Increasing the Cs concentration in the agar ([Cs]agar) on which Arabidopsis were grown reduced shoot growth. Increasing the K concentration in the agar ([K]agar) increased the [Cs]agar at which Cs toxicity was observed. However, although increasing [Cs]agar reduced shoot K concentration ([K]shoot), the decrease in shoot growth appeared unrelated to [K]shoot per se. Furthermore, the changes in gene expression in Cs-intoxicated plants differed from those of K-starved plants, suggesting that Cs intoxication was not perceived genetically solely as K starvation. In addition to reducing [K]shoot, increasing [Cs]agar also increased shoot Cs concentration ([Cs]shoot), but shoot growth appeared unrelated to [Cs]shoot per se. The relationship between shoot growth and [Cs]shoot/[K]shoot suggested that, at a nontoxic [Cs]shoot, growth was determined by [K]shoot but that the growth of Cs-intoxicated plants was related to the [Cs]shoot/[K]shoot quotient. This is consistent with Cs intoxication resulting from competition between K+ and Cs+ for K+-binding sites on essential proteins.

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“…Moreover, we considered that potassium absorption might compete with ammonium absorption because both ions are univalent cations; hence, the soybeans may lack potassium. A lack of potassium has been found to increase cesium absorption [9,12,13]. However, the potassium concentrations in soybean did not decrease with ammonium fertilization.…”

Section: Discussionmentioning

confidence: 99%

Effect of Nitrogen Fertilization on Radiocesium Absorption in Soybean

Nihei

Hirose

Mori

et al. 2016

Radiological Issues for Fukushima’s Revitalized Future

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Radioactive materials that were released during the nuclear accident contaminated the soil and agricultural products. It has become clear that potassium fertilization is effective for the reducing radiocesium concentrations in agricultural crops. However, apart from reports about potassium, few reports have examined how nitrogen (N), which has a large effect on crop growth, contributes to the radiocesium absorption. Focusing on this point, we studied the effect of nitrogen fertilizer on the radiocesium absorption in soybean seedlings. The concentration of radiocesium in the seed of soybean was higher in nitrogen-fertilized plants than in plants grown without fertilizer. The radiocesium concentration in the aboveground biomass increased as the amount of nitrogen fertilization increased. A comparison of the effects of the different forms of nitrogen treatment shows that the highest radiocesium concentration in the aboveground biomass occurred with ammonium sulfate (approximately 3.7 times the non-N), the next highest absorption occurred with ammonium nitrate (approximately 2.4 times the non-N treatment), followed by calcium nitrate (approximately 2.2 times the non-N treatment). Furthermore, the amount of radiocesium in soil extracts was highest with ammonium-nitrogen fertilization. Further study is required to clarify the factors that incur an increase in radiocesium concentration in response to nitrogen fertilization. Special care is required to start farming soybean on fallow fields evacuated after the accident or on fields where rice has been grown before, which tend to have higher available nitrogen than the regularly cultivated fields.

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Accumulation of Potassium, Cesium, and Rubidium in Bean Plants Grown in Nutrient Solutions

Cited by 90 publications

References 7 publications

Tansley Review No. 113

Tansley Review No. 113

Cesium Toxicity in Arabidopsis

Effect of Nitrogen Fertilization on Radiocesium Absorption in Soybean

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