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  • 1
    Electronic Resource
    Electronic Resource
    Can plants exposed to SO2 excrete sulfuric acid through the roots? (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hydroponically grown pea plants (Pisum sativum L., cv. Kleine Rheinländerin) and barley seedlings (Hordeum vulgare L., cv. Gerbel) were fumigated for several days with 1 or 2 μl l−1 SO2. Both species accumulated sulfate during fumigation, although the nutrient medium lacked sulfate. In pea, SO2-dependent sulfate accumulation in different plant parts accounted for 60 percent of the SO2 sulfur which, as calculated from a determination of boundary and stomatal flux resistances had entered the leaves. Up to 55% of the air-borne sulfate was translocated from pea leaves to roots during the period of fumigation, but no or only little sulfate was excreted into the nutrient solution. In contrast, barley retained sulfate in the leaves, and sulfate translocation from shoot to the root system could not be observed. In both species, protons were excreted by the roots. In fumigated plants, proton loss was higher than in untreated controls in pea, but not in barley. In pea, SO2-dependent proton loss into the medium accounted for up to 50% of the sulfuric acid formed from SO2. Proton excretion was strongly dependent on potassium availability in the nutrient medium. Cation uptake by the plants during fumigation was sufficient to compensate for proton loss, suggesting proton/cation exchange at the interface between root and medium. We conclude that by oxidation to sulfuric acid, plants are capable of detoxifying SO2 taken up by the leaves. Depending on plant species, either both protons and sulfate anions can be exported from the leaves, or the proton load on leaf cells can be relieved by proton/cation exchange at the plasmalemma. Finally, the problem of airborne plant acidification may be solved by proton/cation exchange at the level of roots. The burden of acidification is then shifted from the plant to the nutrient medium. Appreciable amounts of sulfate can be excreted neither by pea nor by barley plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb08791.x
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  • 2
    Electronic Resource
    Electronic Resource
    SO2-dependent cation competition and compartmentalization in Norway spruce needles (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ion contents in needles from Norway spruce trees [Picea abies (L.) Karst.] growing in Würzburg and in the SO2-polluted Erzgebirge mountains were analysed to quantify cations which accumulate together with sulphate. In Würzburg there was a positive correlation of potassium (0.680 ± 0.300 Eq Eq−1 SO4−2), magnesium (0.415 ± 0.111 Eq Eq−1 SO4−2) and zinc (0.059 ± 0.006 Eq Eq−1 SO42−). In the Erzgebirge, potassium was also the stoichiometrically most important cation (0–887 ± 0–180 Eq K+ Eq−1 SO42−). All other correlations examined were weak or statistically non-significant. At both sites the calcium content of spruce needles did not depend on the sulphate content. The lack of a role for Ca2+ in neutralizing sulphate is a consequence of the presence of free oxalic acid in needles. Soluble oxalic acid precipitates Ca2+, which thereby becomes unavailable as a counterion for SO42−. The activity coefficients of Ca2+ and oxalate2−, and the solubility product of Ca-oxalate, were determined from in vivo data. It is concluded that the chronic accumulation of atmospheric sulphate in spruce needle vacuoles depletes available potassium and thereby strongly interferes with spruce growth and canopy turnover. This leads to impaired spruce vitality, even at sites where acute SO2 disease symptoms are absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00418.x
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  • 3
    Electronic Resource
    Electronic Resource
    Replacement of nitrate by ammonium as the nitrogen source increases the salt sensitivity of pea plants. I. Ion concentrations in roots and leaves (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pea seedlings (Pisum sativum L. cv ‘Kleine Rheinlän-derin’) were grown hydroponically in solutions containing either nitrate (3 or 14 mol m−3) or ammonium (3 mol m−3) as the nitrogen source. Ammonium nutrition as such had no negative effect on plant biomass production, but drastically increased the sensitivity to moderate salinity (50 mol m−3 NaCl). The reasons for this effect are investigated here and in a subsequent paper. The appearance of visible symptoms of salt damage (wilting of marginal leaf areas followed by progressive necrosis) was paralleled by the development of several characteristic modifications in the solute and metabolite contents. Major changes were: (i) high salt (NaCl) accumulation in leaves; (ii) accumulation of ammonium (up to 20 mol m−3) and amino acids (up to 110 mol m−3) in leaves, but at decreased ammonium uptake rates; and (iii) decreased protein content. In a comparison paper we report on the subcellular distribution of salts, ammonium and metabolites under the above conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb02019.x
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  • 4
    Electronic Resource
    Electronic Resource
    ATP-dependent carbon transport in perfused Chara cells (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbon transport across the plasma membrane, and carbon fixation were measured in perfused Chara internodal cells. These parameters were measured in external media of pH 5·5 and pH 8·5, where CO2 and HCO3- are, respectively, the predominant carbon species in both light and dark conditions. Cells perfused with medium containing ATP could utilize both CO2 and HCO3- from the external medium in the light. Photosynthetic carbon fixation activity was always higher at pH 5·5 than at pH 8·5. When cells were perfused either with medium containing hexokinase and 2-deoxyglucose to deplete ATP from the cytosol (HK medium) or with medium containing vanadate, a specific inhibitor of the plasma membrane H+-ATPase (V medium), photosynthetic carbon fixation was strongly inhibited at both pH 5·5 and 8·5. Perfusion of cells with medium containing pyruvate kinase and phosphoenolpyruvate (PEP) to maximally activate the H+-ATPase (PK medium), stimulated the photosynthetic carbon fixation activities. Oxygen evolution of isolated chloroplasts and the carbon fixation of cells supplied 14C intracellularly were not inhibited by perfusion media containing either hexokinase and 2-deoxyglucose or vanadate. The results indicate that Chara cells possess CO2 and HCO3- transport systems energized by ATP and sensitive to vanadate in the light. In the dark, intact cells also fix carbon. By contrast, in cells perfused with medium containing ATP, no carbon fixation was detected in 1 mol m -3 total dissolved inorganic carbon (TDIC) at pH 8·5. By increasing TDIC to 10 mol m-3, dark fixation became detectable, although it was still lower than that of intact cells at 1mol m-3 TDIC. Addition of PEP or PEP and PEP carboxylase to the perfusion media significantly increased the dark-carbon fixation. Perfusion with vanadate had no effect on the dark-carbon fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1993.tb00483.x
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  • 5
    Electronic Resource
    Electronic Resource
    Rapid modulation of nitrate reductase in leaves and roots: Indirect evidence for the involvement of protein phosphorylation/dephosphorylation (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 89 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrate reductase activity (NRA; NADH-nitrate reductase, E. C. 1.6.6.1) has been measured in extracts from leaves of spinach (Spinacia oleracea L.) in response to rapid changes in illumination, or supply of CO2 or oxygen. Measured in buffers containing magnesium, NRA from leaves decreased in the dark and increased again upon illumination. It decreased also, when CO2 was removed in continuous light, and was reactivated when CO2 was added. Nitrate reductase (NR) from roots of pea (Pisum sativum L.) was also rapidly modulated in vivo. It increased under anaerobiosis and decreased in air or pure oxygen. The half time for inactivation or reactivation in roots and leaves was 5 to 30 min.When spinach leaves were harvested during a normal day/night cycle, extractable NRA was low during the night, and high during daytime. However, at any point of the diurnal cycle, NR could be brought to a similar maximum activity by preincubation of the desalted leaf extract with AMP and/or EDTA. Thus, the observed diurnal changes appeared to be mainly a consequence of enzyme modulation, not of protein turnover. In vivo, the reactivation of the inactivated enzyme from both leaves and roots was prevented by okadaic acid, and inhibitor of certain protein phosphatases. Artificial lowering of the ATP-levels in leaf or root tissues by anaerobiosis (dark), mannose or the uncoupler carbonyl cyanide m-chlorophenyl hydrazon (CCCP), always brought about full activation of NR.By preincubating crude leaf or root extracts with MgATP, NR was inactivated in vitro. Partial purification from spinach leaves of two enzymes with molecular masses in the 67 kD and 100 kD range, respectively, is reported. Both participate in the ATP-dependent inactivation of NR.Alltogether these data indicate that NR can be rapidly modulated by reversible protein phosphorylation/dephosphorylation, both in shoots and in roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb05213.x
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  • 6
    Electronic Resource
    Electronic Resource
    Replacement of nitrate by ammonium as the nitrogen source increases the salt sensitivity of pea plants. II. Inter- and intracellular solute compartmentation in leaflets (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 17 (1994), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pea plants (Pisum sativum L. cv. ‘Kleine Rheinländerin’) grown on ammonium or nitrate as the sole nitrogen source were treated with 50 mol m−3 NaCl. Four days after salt addition, ammonium-grown plants developed the first visible damage symptoms (wilting of leaflets, starting from the margins). Salt-treated, nitrate-grown plants were not affected during the experimental period. In order to obtain a better understanding of this differential salt sensitivity, we investigated the inter- and intracellular ion compartmentation of leaflets under both nutritional conditions by analysing ion concentrations in the apoplastic space, in chloroplasts and in protoplasts. When the leaves of nitrate- and ammonium-grown plants had attained similar sodium and chloride contents (after different times of exposure to salinity), the latter had a considerably lower chloroplastic chloride (and also sulphate) concentration. The results suggest that the intracellular compartmentation capacity of ammonium-grown plants is considerably lower than that of nitrate-grown plants. Ion toxicity appeared to initiate breakdown of metabolism in parts of the mesophyll tissue of ammonium-grown plants, causing an abrupt release of solutes into the apoplast, which coincided with the appearance of visible damage. Although the ammonium concentrations in leaves increased dramatically in the later phases of damage development, they were too low to cause the collapse of electrochemical gradients at the time at which damage became visible. Thus, the reason for a lower compartmentation capacity under ammonium nutrition remains as yet unclear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1994.tb02020.x
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  • 7
    Electronic Resource
    Electronic Resource
    Leaching of solutes by the action of acidic rain: a comparison of efflux from twigs and single needles of Picea abies (L. Karst.) (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Leaching of inorganic cations (K+, Mg2+) and in some cases of inorganic anions and sugars from detached twigs and single needles of spruce Picea abies L. Karst.) in the presence of acid rain (H2SO4, 1 mol m−3) or salt solutions (Na2 SO4, 1 mol m−3) was examined under laboratory conditions. Cation leaching (as percentage of the total water soluble ion content of the tissue per hour) was: K+: 0.01-0.02%; Mg2+: 0.005-0.01%; Ca2+: 0.1-0.2%. Leaching rates of anions were even lower than that and concentrations in the leachate were often below the detection limit of anion chromatography. Spraying with H2SO4 (pH 2.95, 1 mol m−3) increased leaching only transiently. Similar effects were found when Na2SO4 was used instead of H2SO4. The transiently enhanced leaching was apparently due to H+/cation or cation/cation exchange at the twig or leaf surfaces. Feeding of K+ or Al3+ through the stems increased leaching of all cations within a few hours, again demonstrating rapid ion exchange in the apoplast. Leaching of potassium and magnesium from single needles occurred at similar relative rates as from twigs. Loss of Ca2+ ions, however, was even smaller from needles than from twigs. Apparently, a large part of the Ca2+ lost from twigs originated from the bark and not from the needles. Efflux of ions from longitudinal needle sections was about 1000 times taster than the rates obtained with intact needles, indicating that the cuticle was the main barrier Preventing solute loss. In relation to the total amount of mineral nutrients in trees, leaching is considered to be too small to be the primary cause of damage to trees stressed by acid rain, as has been suggested in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01920.x
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