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1.
Summary Bush bean plants were exposed to either Rb 86 or Cs 137 for 24 hours with different monovalent cations as carriers in single-salt solutions except for the presence of 10 −4
M CaCl 2. Ratio of uptake of the radionuclides at 10 −3 to 10 −2
M was used as an index of the carrier ability of various cations. Different monovalent cations decreased uptake of Cs 137 and its transport to shoots unequally when 10 −2
M salts were compared with 10 −3
M salts. Rubidium and cesium salts decreased Cs 137 uptake equally but potassium salts were less effective in decreasing uptake when the ratios of the two concentrations were
considered. All monovalent cations decreased uptake of Cs 137 at the 10 −2
M carrier concentration but some did not at 10 −3
M. Nitrate nitrogen was a big factor in these results. Cesium and rubidium salts were most effective. Potassium appeared to
increase Cs 137 transport to shoots particularly at 10 −3
M KNO 3. Only cesium, rubidium, and potassium salts decreased uptake of Rb 86 when 10 −2
M salts were compared with 10 −3
M. Rubidium and cesium salts decreased uptake essentially equally and potassium salts again were less effective. All nitrate
salts tended to increase Rb 86 transport to shoots more consistently than with Cs 137. It is concluded that absorption and transport to shoots were not equivalent for potassium, rubidium, and cesium. 相似文献
2.
Summary When nonexchangeable absorption of Rb 86, Na 22, and Cs 137 by bush bean ( Phaseolus vulgaris L. var. Improved Tendergreen) was determined at different root temperatures and with and without Ca additions or pretreatments,
a strong interaction between temperature and Ca was observed. Ca inhibited Rb 86 absorption markedly at low temperatures but had less effect on Cs 137. Absorption of Na 22 was inhibited by Ca at both low and high temperatures. Little effect for Ca with sometimes a Viets effect was observed at
high temperature for Rb but not for Cs or Na. Ratio pairs of Rb, Ca, and Na were used as an index of similarity of absorption
mechanisms. Cs and Rb, and Na and Rb appeared to be absorbed by different mechanisms at 10 −3
M as indicated by temperature and Ca responses. Nitrate-N stimulated uptake of Rb only at high temperature with or without
Ca but not at low temperature. Ca in the pretreatment tended to result in greater long distance transport to shoots of Rb 86 and Cs 137 for the high temperature but Ca in the test solution slightly decreased the long distance transport. The data are discussed
in terms of the Viets effect and of a possible role of Ca in synthesis of transport proteins. 相似文献
3.
Pea plants grown in nutrient solution in which K + ions were equimolarly replaced with Na +, NH 4 + or Rb + did not show morphological symptoms of potassium-deficiency. The activity of diamine oxidase in these plants was higher than in controls. Similarly higher diamine oxidase activity was found in plants grown in a complete nutrient solution supplemented with putrescine. 相似文献
4.
Alfalfa ( Medicago sativa; L.) plants susceptible (S) and resistant (R) to the bacterial wilt were fed via roots with a nutrient solution labelled with 86Rb +, at different times after inoculating them with Corynebacterium insidiosum ( McCull.) H. L. Jens. The infection did not influence 86Rb + uptake per plant in the course of a 14-day-period following inoculation, however it did affect its distribution differentially
in the S- and the R-plants. 86Rb + uptake was significantly decreased due to the infection in the S-plants on the day 49 after the inoculation (a 4-h-exposure
to 86Rb +), with the iona also being more slowly translocated to the shoots in diseased S-plants than in diseased R-plants. Likely
factors causing these effects and their relationship to alfalfa resistance to the bacterial wilt are discussed. 相似文献
5.
Summary The successful use of Rb 86 as a tracer for potassium in rice nutrition studies is related to the relative uptake of these two nutrient elements and
the estimation of potassium by Rb 86 analysis. Results obtained under nutrient culture condition showed that the ratio of rubidium: potassium in the substrate
was similar to that in the plant and the amount of potassium determined by conventional method was comparable to that of radiochemical
analysis of Rb 86. 相似文献
6.
The influx of Rb + into the roots of two barley varieties ( Hordeum vulgare L. cv. Salve and cv. Ingrid) from a K +-free 86Rb-labelled nutrient solution with 2.0 m M Rb +, was checked at intervals from day 6 to day 18. The control plants were continuously grown in complete nutrient solution containing 5.0 m M K +, while two other groups of plants were grown in K +-free nutrient solution starting on day 6 and between day 6 and day 9, respectively. The pattern of Rb + influx was similar for both varieties, although their efficiencies in absorbing Rb + were different. The relationship between Rb + influx and K + concentration of the root could be interpreted in terms of negative feedback through allosteric control of uptake across the plasmalemma of the root cells. Hill plots were bimodal, but in the opposite direction. The Hill coefficients, reflecting the minimum number of interacting allosteric binding sites for K + (Rb +), were low (≤–3.0). It is discussed whether the threshold value, that is the breaking point in the Hill plot, is indicative of a changed efficiency of transporting units for K + (Rb +) transport to the xylem. Moreover, feedback regulation might be involved in transport of K + between root and shoot. The variation in K + concentrations in the roots and shoots of control plants were cyclic but in phase opposition despite an exponential growth. The average K + concentration varied only slightly with age. 相似文献
7.
Specific binding sites for potassium, which may be components of the carriers for active transport for K in Chlorella, were characterized by their capacity to bind rubidium. A dense suspension was allowed to take up Rb 86 from a low concentration of Rb 86 and a high concentration of ions which saturate non-specific sites. The amount bound was derived from the increase in the external concentration of Rb 86 following addition of excess potassium. The sites were heterogeneous. The average affinity of Rb and various other ions for the sites was determined by plotting the degree of displacement of Rb 86 against log molar concentration of the individual ions. Interpolation gave the concentration for 50 per cent displacement of Rb, which is inversely related to affinity. The order of affinity was not changed when the cells were frozen, or boiled either in water or in 70 per cent ethanol. The affinity is maximal for ions with a crystalline radius of 1.3 to 1.5 A and a high polarizability, and is not related to the hydrated radius or valency. It is suggested that binding groups in a site are rigidly arranged, the irregular space between them being 2.6 to 3.0 A across, so that affinity is high for ions of this diameter and high polarizability. 相似文献
8.
Barley ( Hordeum vulgare L. cv Halcyon) seedlings which had been grown in full strength complete inorganic nutrient media (containing 6 millimolar K +) had high internal K + concentrations and low values of K + ( 86Rb +) influx when influx was measured from solutions containing 100 micromolar K +. Transfer of these plants to solutions lacking K + resulted in significant reductions of root and shoot K + concentrations and values of K + ( 86Rb +) influx increased by greater than 10-fold within 3 days. When plants treated in this way were returned to complete solutions, containing K +, the changes induced by K + deprivation were reversed. Parallel studies of microsomal membranes by means of SDS-PAGE demonstrated that the expression of a group of polypeptides increased or decreased in parallel with changes of K + ( 86Rb +) influx. Most prominent of these were 45 and 34 kilodalton polypeptides which specifically responded to K + status of the barley plants; their expression was not enhanced by N or P deprivation. The 45 kilodalton polypeptide was susceptible to degradation by a membrane associated protease when microsomes were washed in buffer containing 0.2 millimolar PMSF. This loss was prevented by increasing PMSF concentration to 2 millimolar. 相似文献
9.
The influence of alkali ions on the circadian leaf movements of Oxalis regnellii Mig. was investigated. Ions were given to the oscillating system via the transpiration stream of cut stalks in nutrient medium. Chloride solutions of Rb +, Cs +, Na + and K + were tested and the results compared to previously published LiCl-results. The period of the circadian leaf movements was unaffected by a continual addition of Na + or K + to the nutrient medium (at least up to 40 m M). Rb +, in the concentration of 2.5 or 5 m M, caused a shortening of the period when applied continuously. Rb + concentrations up to 60 m M were tested. Cs + ions caused only lengthenings of the circadian period. Cs + concentrations up to 40 m M were tested. Cs + resembled Li + in producing period lengthenings, but was not as effective as Li + when compared on a concentration basis. Toxicity of the effective ions was in the following order: Li +Cs +Rb +, Rb + pulses (50 m M, 4 h) phase-shifted the rhythm and caused advances. A phase response curve was determined and the maximum steady state advances were of the order of 1 h. The dual effect of the Rb + ions is discussed and is assumed to be due to two counteracting processes, exemplified by Rb +-sensitive ATPase-controlled pumping processes and protein synthesis. For comparison, the effects of Rb + and Li + in human depressive disorders is also discussed in relation to their influence on circadian systems. It is emphasized that Rb + and K + behave differently and are not interchangeable in their action on circadian systems. 相似文献
10.
Water extract of stinging nettle ( Urtica dioica) has a growth stimulating effect on plants. This investigation elucidated effects of nettle water on uptake and transport
of N, P and K. Tomato plants ( Solanum lycopersicum L. cv. Dansk export) were grown in sand culture 6–8 weeks. Plants were supplied with nettle water and nutrient solution was
used as a control medium. Uptake and transport of N, P and K + were determined with isotopes ( 15N, 32P and 86Rb + as a tracer for K +) and ion-selective electrodes and in exudation experiments.
A 15% higher uptake of nitrogen ( 15N assay) was found after nettle water treatment compared with the nutrient solution control. The total amount of nitrogen
was also higher in plants cultivated with nettle water. Transport of inorganic and organic nitrogen, measured in exudation
experiments, was more than 50% higher for plants supplied with nettle water compared with plants supplied with nutrient solution.
In contrast, nettle water had no effect on uptake, transport or total amount of phosphorus and potassium in the plants.
Experiments in hydroculture showed that nettle water had a strong pH-elevating effect. Uptake of NH
4
+
was strongly stimulated by nettle water compared with nutrient solution. By holding pH at a constant level during the uptake
period for 6 h, the uptake of NH
4
+
from nettle water was significantly lower when no adjustment of pH was made. Consequently a good deal of the NH
4
+
uptake enhancement by nettle water could be explained by pH-stimulation. Assays with the uncoupler/inhibitor 2,4-dinitrophenol
(DNP) and dichlorophenyl-dimethyl-urea (DCMU) showed that uptake of nitrogen from nettle water was less metabolically-linked
than uptake from a corresponding nutrient solution. All together, nettle water seems to stimulate the uptake of nitrogen,
but not phosphorus or potassium. 相似文献
11.
The wheat root high-affinity K + transporter HKT1 functions as a sodium-coupled potassium co-uptake transporter. At toxic millimolar levels of sodium (Na +), HKT1 mediates low-affinity Na + uptake while potassium (K +) uptake is blocked. In roots, low-affinity Na + uptake and inhibition of K + uptake contribute to Na + toxicity. In the present study, the selectivity among alkali cations of HKT1 expressed in Xenopus oocytes and yeast was investigated under various ionic conditions at steady state. The data show that HKT1 is highly selective for uptake of the two physiologically significant alkali cations, K + and Na + over Rb +, Cs + and Li +. In addition, Rb + and Cs +, and an excess of extracellular K + over Na +, are shown to partially reduce or block HKT1-mediated K +-Na + uptake. Furthermore, K +, Rb + and Cs + also effectively reduce outward currents mediated by HKT1, thereby causing depolarizations. In yeast, HKT1 can produce high-affinity Rb + uptake at approximately 15-fold lower rates than for K +. Rb + influx in yeast can be mediated by the ability of the yeast plasma membrane proton pump to balance the 35-fold lower HKT1 conductance for Rb +. A model for HKT1 activity is presented involving a high-affinity K + binding site and a high-affinity Na + binding site, and competitive interactions of K +, Na + and other alkali cations for binding to these two sites. Possible implications of the presented results for physiological K + and Na + uptake in plants are discussed. 相似文献
12.
Summary Lowland rice plants were grown in double isolated containers, where shoot base was dipped in Cs 137 contaminated water and roots in Cs 134 contaminated nutrient solution and vice versa. The plants were collected after six weeks and plant sample activity determined by γ-spectrometry. Radiocaesium is absorbed
by the shoot base and distributed in the different organs of the plant; the transfer coefficient being higher for water-plant
than between nutrient solution-plant. Concentration factors obtained and exchangeability of Cs fixed by the plant vary with
the radioisotope. Such a behavior may find an explanation in the stable Cs content of the medium. No equilibrium is observed
in the plant between two radioisotopes of the same element absorbed by different plant organ.
This publication is contribution no. 691 of the EURATOM Biology Division. 相似文献
13.
At salt concentrations of 0.1 m M as well as of 5.0 m M, the 22Na + absorption capacity of bean ( Phaseolus vulgaris L. cv. ‘Brittle Wax’) leaf tissue increased during the period of leaf expansion and decreased rapidly after leaf maturation. The absorption capacity for 86Rb + and 42K + was highest in very young leaves and decreased continuously in expanding and in mature leaves. The 86Rb + absorption capacity of mature leaves was not increased by detopping the plants; this senescence-retarding treatment more than doubled 2Na + absorption. The absorption of 22Na + by bean-leaf slices was not enhanced by light, whereas 86Rb + and 42K + absorption was much affected. Previously absorbed 86Rb + and 42K + were more available for exchange than 22Na +. 相似文献
14.
Uptake of Rb + was investigated in 12-day-old intact plants of sunflower ( Helianthus annum L. var. californicus) which had been cultivated or pretreated in nutrient solutions with various K + concentrations. The relationship between Rb + influx and K + concentration of the roots indicated regulation of Rb + uptake by allosteric inhibition of the uptake mechanism. A constant passive influx occurred contemporaneously with the active uptake as shown by experiments at 0°C or with 2,4-dinitrophenol. The allosteric regulation of ion carrier activity occurred after a time lag of up to 1 h after the change of external solution. In experiments involving Rb + treatments of K +-deficient plants, the synthesis of carriers for transport of Rb + could be demonstrated. A model including allosteric regulation of Rb + uptake in roots is discussed. 相似文献
15.
Spring wheat plants were grown in a 137Cs labelled nutrient solution, either in the presence or absence of NH 4 as a secondary N source. Between 11 and 64 days after sowing (DAS), plants were harvested on nine occasions. The plants supplied with NH 4 and NO 3 had lower root 137Cs Activity Concentrations (AC) than those supplied with NO 3 only. Shoot AC were equal in both nutrition treatments. Shoot and root 137Cs AC (dry weight basis) showed the same trends with plant age in both nutrition treatments. Shoot AC almost doubled between 11 and 28 DAS after which they gradually decreased concomitant with a similar decrease in K concentrations. Root AC were always higher than shoot AC and increased to a maximum at 35 DAS after which they fluctuated. Expressed on a tissue water basis, the 137Cs AC varied less during plant age than did dry weight based AC. Furthermore, root and shoot AC expressed on a tissue water basis were almost equal. It is shown that the initial increase in 137Cs AC in both root and shoot can largely be explained by the initial dilution of absorbed 137Cs in the unlabelled seedling tissues. No correlation was found between K and 137Cs distribution among ears, leaves, stems and roots in 64 old wheat plants. NH 4 as a secondary N source in a nitrate nutrient solution marginally affected 137Cs distribution.Abbreviations AC
activity concentrations
- DAS
days after sowing
FAX no corresponding author: +3216321997 相似文献
16.
Earlier studies have demonstrated close inverse relationships between Rb + concentrations in plants and pH or base (including K +) saturation of soils. This study aims at elucidating conditions in soils influencing plant uptake of Rb +. Growth experiments with Carex pilulifera L. were performed, modifying the acidity and K + supply of acid soils and solutions. We were unable to assess any reduction in Rb + uptake by adding precipitated CaCO 3 to acid soil unless pH was raised to near neutrality. Though not fully compensating the loss of soil solution K +and exchangeable K + from uptake by the growing plants, soil treated with 0.5 mM K + (as KCl) reduced the Rb + concentration in the shoots by 40% without measurably changing soil pH. Experiments varying the pH and K + concentration of a nutrient solution (20% Hoagland), spiked with 6 uM Rb +, clearly demonstrated that plant uptake of Rb + and K + was unaffected by acidity in the pH range 3.6–5.0 tested, whereas Rb + uptake was reduced by ca. 50%, when K + concentration was increased from 1.2 to 3.6 mM. The sensitivity of this reaction indicates that shortage or low availability of K + controls Rb + uptake from acid soils, being probably more important than soil acidity per se. Secondary effects of high soil acidity, such as leaching losses of K +, might also be of importance in accounting for the high uptake of Rb + from such soils. It is suggested that leaf analysis of Rb + may be used as a method to assess early stages of K + deficiency in plants on acid soils. 相似文献
17.
Influx of Rb +( 86Rb +) and Ca 2+ ( 45Ca 2+) in roots of intact winter wheat ( Triticum aestivum L. cv. Weibulls Starke II) was determined at intervals before, during and after exposure to cold acclimation conditions (2°C and 8 h light period). The plants were grown in nutrient medium of two ionic strengths. During the initial two weeks of growth at 16°C and 16 h light period, Rb + influx into roots decreased with increasing age, probably as a consequence of a decreasing proportion of metabolically active roots. The presence of 10 ?4M 2,4-dinitrophenol (DNP) reduced Rb + influx to a low and constant level, indicating that metabolic influx was the dominant process. In contrast, Ca 2+ influx in plants grown in full strength nutrient solution was higher in the presence than in the absence of DNP. This effect may have been due to an active extrusion mechanism mediating re-export of absorbed Ca 2+( 45Ca 2+) during the uptake experiment. With the metabolic uncoupler inhibiting such extrusion the Ca 2+( 45Ca 2+) influx mesured would increase. During cold treatment, Rb + influx remained at a low level, and was further decreased when DNP was present in the uptake solution. This effect may have been due to inhibition of residual active influx of Rb + at 2°C by the uncoupler and/or to a decrease in membrane permeability. In contrast to Rb +, Ca 2+ influx increased during cold treatment, which could again be explained as inhibition of re-export. The presence of DNP reduced Ca 2+ influx at 2°C, indicating decreased membrane permeability by DNP at low temperature. After transfer of plants from cold acclimation conditions to 16°C, Rb + and Ca 2+ influx increased in plants grown at both ionic strengths. Influx levels were independent of the length of the cold acclimation period (1, 6 and 8 weeks), but the patterns were different for the two ions. After each of the cold acclimation periods, Rb + influx increased during the first week and decreased or remained at the same level during the second week, while Ca 2+ influx always decreased during the second week of post-cold treatment. 相似文献
18.
The classic compartment analysis of ion efflux from roots is often applied with the assumption that there is a system of 3 compartments in series. However, complex ion transport across the root tissues, as well as influences from the shoot, may complicate the picture. The present experiments were performed to study the immediate effects that excision of the shoot before the experiment exerts on the efflux of Rb +( 86Rb +) and of K +( 86Rb +) from 9-day-old roots of plants of barley ( Hordeum vulgare L. cv. Salve). The efflux from high K + and low K + roots of intact and detopped plants were compared. After excision of the shoot of high K + plants, a marked increase in efflux was observed after 2.5 h with a maximum at about 7 h. The increase in efflux was seen as a peak in plots of efflux versus time. Excision of the shoot from low K + roots did not give rise to a consistent increase in efflux. Regular K + ion efflux curves were observed from roots of intact plants of high or low K + status. Furthermore, after a pulse treatment of 9-day-old roots of intact plants of high or low K + status with a solution containing Rb +( 86Rb +), the Rb +( 86Rb +) transport to the shoots was not reduced during the following 3 h in unlabelled solution. It is suggested that both the peak appearing in the efflux plots and the maintained tracer transport to the shoots after transfer of the roots to an unlabelled solution indicate the existence of a K +/Rb + transport system in the symplasm of the roots that has only a slow exchange with the bulk cytoplasm and vacuoles. 相似文献
19.
Phosphate-starved Chlorella pyrenoidosa cells formed polyphosphate bodies (PB) upon transfer into nutrient solutions containing phosphate and potassium, or another monovalent cation, such as Na +, NH 4+, Li +, or Rb +. The phenomenon was studied by chemical analyses, light microscopy, and electron microscopy. When the P-starved cells were transferred into a complete nutrient solution containing 100 micromolar P, they accumulated large quantities of P and K within several hours. The accumulation was accompanied by a corresponding appearance of PB in the cells. The absence of K from the medium prevented appreciable P accumulation and PB formation, but omitting Ca or Mg did not. The P-starved cells exposed to a simple solution of at least 20 micromolar H3PO4 and 100 micromolar KHCO3 responded in a similar manner as the cells exposed to the complete nutrient solution. However, the PB appeared structurally different. It is proposed that monovalent cations are essential for PB formation in C. pyrenoidosa. K is suggested to be a major component of PB formed in K-sufficient media. 相似文献
20.
Summary Normal frog sartorius muscles and muscles in which a major portion of the intracellular K + was reversibly replaced by Rb + or Cs + were frozen, freeze-dried and embedded without chemical fixation or staining. Dry-cut sections of these preparations reveal striation patterns with higher contrast than those of wet-cut sections of the same preparation. The results suggest that in the living state the alkali metal ions are mainly localized in the A bands and Z lines of myofibrils. This idea is confirmed by a new autoradiographic technique by means of which the distribution of Rb + and Cs + in frozen-hydrated single muscle fibers has been investigated. The findings support the association-induction hypothesis according to which most cell K + and other alkali-metal ions are not free in cell water but are adsorbed to beta- and gamma-carboxyl groups of cell proteins. 相似文献
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