Wolfram R Ullrich

Publications (17)74.85 Total impact

• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art: EPILOGUE.

  Riklef Kandeler, Wolfram R Ullrich
  Journal of Experimental Botany 09/2009; 60(15):4219-20. · 5.36 Impact Factor
• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art: DECEMBER: cross-roses and rose crosses.

  Riklef Kandeler, Wolfram R Ullrich
  Journal of Experimental Botany 09/2009; 60(15):4217-8. · 5.36 Impact Factor
• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art.

  Riklef Kandeler, Wolfram R Ullrich
  Journal of Experimental Botany 08/2009; 60(13):3611-3. · 5.36 Impact Factor
• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art.

  Riklef Kandeler, Wolfram R Ullrich
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  ABSTRACT: It is a great pleasure to meet the first blue flowers of columbine when walking along woodland edges in May, but it is becoming a rarity in the wild in central Europe. Columbine petals have a quite complicated structure inviting close inspection. Their beauty has attracted poets and painters and they have accumulated symbolic and transcendental meanings, an uplifting plant for scientists and artists alike.
  Journal of Experimental Botany 05/2009; 60(6):1535-6. · 5.36 Impact Factor
• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art: JUNE: Lilies.

  Riklef Kandeler, Wolfram R Ullrich
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  ABSTRACT: Lilies are a group of the most conspicuous flowers of early summer. Thousands of cultivated varieties are available from modern lists. However, wild lilies are distinctive enough to have acquired religious and cultural significance in many ancient cultures. It is fascinating to follow these cultural aspects from antiquity to the modern age, although there are far too many associations for them all to be covered here.
  Journal of Experimental Botany 05/2009; 60(7):1893-5. · 5.36 Impact Factor
• Article: Symbolism of plants: examples of European-Mediterranean culture presented with biology and history of art.

  Riklef Kandeler, Wolfram R Ullrich
  Journal of Experimental Botany 02/2009; 60(1):6-8. · 5.36 Impact Factor
• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art.

  Riklef Kandeler, Wolfram R Ullrich
  Journal of Experimental Botany 02/2009; 60(12):3297-9. · 5.36 Impact Factor
• Article: Ammonium uptake in Lemna gibba G 1, related membrane potential changes, and inhibition of anion uptake

  Wolfram R. Ullrich, Marie Larsson, Carl-Magnus Larsson, Sigrid Lesch, Anton Novacky
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  ABSTRACT: In N-starved (−N) fronds of Lemna gibba L. G 1, NH4+ uptake rates were several-fold those of NO3−-supplied (+N) fronds. NO3−, uptake in +N-plants was slow and not inhibited by addition of NH4+. However, in −N-plants with higher NO3− and still higher NH4+ uptake rates, addition of NH4+ immediately reduced the NO3− uptake rates to about one third until the NH4+ was consumed. The membrane potential (Em) decreased immediately upon addition of NH4+ in all fronds, but whereas depolarisation was moderate and transient in +N-plants, it was strong, up to 150 mV, in N-starved plants, where Em remained at the level of the K+ diffusion potential (ED) until NH4+ was removed. In N-starved plants NH4+ uptake and membrane depolarisation showed the same concentration dependence, except for an apparent linear component for uptake. Phosphate uptake was inhibited by NH4+ similarly to NO3− uptake, but only in P- and N-starved plants, not after mere P starvation. Influx of NO3− and H2PO 4− into the negatively charged cells of Lemna is mediated by anion/H+ cotransport, but NH4+ influx can follow the electrochemical gradient. Its saturating component may reflect a carrier-mediated NH4+ uniport, the linear component diffusion of NH4+ or NH3. Inhibition of anion/H+ cotransport by high NH4+ influx rates may be due to loss of the proton-driving force, Δμ̃H+, across the plasmalemma. Reversible inhibition by NH4+ of the H+ extrusion pump may contribute to the finding that Δμ̃H+ cannot be reconstituted in the presence of higher NH4+ concentrations.
  Physiologia Plantarum 04/2006; 61(3):369 - 376. · 3.11 Impact Factor
• Article: Generation and possible roles of NO in plant roots and their apoplastic space.

  Christine Stöhr, Wolfram R Ullrich
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  ABSTRACT: In recent years, three different enzymatic pathways and a few non-enzymatic reactions have been proposed for the generation of NO in plant roots. Two of the enzymatic pathways are located in the cytosol of the plant cells, whereas the third is exclusively located in the root plasma membrane facing the apoplast from where it seems to interact with nitrate metabolism by producing signals. A response of the NO pathways to external nitrate concentrations by preventing excess nitrate nutrition, particularly in the apoplast, as well as a regulatory role in root morphogenesis of NO in interaction with plant hormones is suggested. Other functions of NO, those in stimulating plant defence reactions against pathogens and against abiotic stress are reported. In addition to enzymatic NO formation by the plant, sources of NO in the soil, and hence in the rhizosphere from bacterial nitrification and denitrification, are discussed in view of their possible interaction with the plant roots. A synoptical perspective is given on the assumed roles of apoplastic NO in plant roots, based upon known facts and with some assumptions about the gaps in current knowledge.
  Journal of Experimental Botany 01/2003; 53(379):2293-303. · 5.36 Impact Factor
• Article: Soluble and membrane‐associated nitrate reductases in the dinoflagellate Peridinium gatunense

  FEDERICO G. WITT, CHRISTINE STÖHR, WOLFRAM R. ULLRICH
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  ABSTRACT: An improved method of cell fractionation allowed the extraction of soluble (sNR) and membrane-associated (mNR) forms of nitrate reductase (NR) from a dinoflagellate, even though in previous studies only mNR had been found in these algae. Both activities were assayed in cell-free extracts of Peridinium gatunense from Lake Kinneret, Israel, after disruption of the cells and differential centrifugation. In the cultures used, sNR showed much higher NO3−-reducing activity. Only a low proportion, 2.5–3% of NR activity, was found to be associated with mNR. Moreover, mNR comprised two forms as indicated by protein solubilization: a tightly membrane-bound and a more weakly attached NR. Ascorbate inhibited all NR activities, but that of mNR recovered after its removal. Polyvinyl pyrrolidone (PVP) and DTT also diminished sNR and mNR activities. For both enzymes, pH optima (7.65) and temperature optima (13–25°C) were similar, and agreed with those for optimum growth of P. gatunense both in culture and in the lake. The most efficient electron donor was NADH, though NADPH sustained low NR activities. Carboxylic anions such as succinate and malate did not support any reduction of NO3−, nor did they cause any stimulation of sNR or mNR activities. Both forms of NR showed a high affinity for their substrates: Km was c. 10 μM for NO3− and c. 5 μM for NADH. The high efficiency of NO3− assimilation by Peridinium seems to be limited mainly by energy under otherwise optimal nutritional conditions and, at low nitrate concentrations, the low Km may be one of the main reasons for the high competitivity of this alga in Lake Kinneret.
  New Phytologist 01/2002; 142(1):27 - 34. · 6.64 Impact Factor
• Article: Kinetic characterization of succinate‐dependent plasma membrane‐bound nitrate reductase in tobacco roots 1

  Stefanie Wienkoop, Wolfram R Ullrich, Christine Stöhr
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  ABSTRACT: Plasma membrane-bound nitrate reductase (PM-NR) of tobacco (Nicotiana tabacum L. cv. Samsun) roots reduces nitrate with NADH and/or succinate as electron donor. The present paper reports on significant differences of the succinate-dependent activity (succ-PM-NR) to known NADH-dependent soluble and plasma membrane-bound NR. The experiments were performed with plasma membrane vesicles containing the hydrophobic PM-NR. In a temperature course, succ-PM-NR activity attained the highest rates of total activity (succinate-nitrate) at 50°C, NADH-dependent PM-NR (NADH-PM-NR) only at 30°C. The temperature responses of partial reactions with domains of NR diverged, but indicated that the heme domain was the most sensitive to high temperatures and could limit succ-PM-NR. In contrast to NADH, succinate did not supply electrons to ferricyanide reduction. The pH optima of the overall reaction with succinate were 5.6 and 8.0 at 30°C, pH 7.0 at 50°C, with a much higher rate in the latter case. The affinities of succ-PM-NR for both substrates (succinate and nitrate) were highest at pH 5.6 and higher at 50°C than at 30°C. Malonate showed competitive inhibition with succinate, but not with NADH as substrate. We assume that structural differences in the flavin domain of at least one of the subunits of root PM-NR may be responsible for the succinate-dependent in addition to the NADH-dependent activity, but a more detailed analysis is necessary.
  Physiologia Plantarum 01/2002; 105(4):609 - 614. · 3.11 Impact Factor
• Article: A plasma membrane-bound enzyme of tobacco roots catalyses the formation of nitric oxide from nitrite

  Christine Stöhr, Frank Strube, Gisela Marx, Wolfram R. Ullrich, Peter Rockel
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  ABSTRACT: Purified plasma membranes (PMs) of tobacco (Nicotiana tabacum L. cv. Samsun) roots exhibited a nitrite-reducing enzyme activity that resulted in nitric oxide (NO) formation. This enzyme activity was not detected in soluble protein fractions or in PM vesicles of leaves. At the pH optimum of pH 6.0, nitrite was reduced to NO with reduced cytochrome c as electron donor at a rate comparable to the nitrate-reducing activity of root-specific succinate-dependent PM-bound nitrate reductase (PM-NR). The hitherto unknown PM-bound nitrite: NO-reductase (NI-NOR) was insensitive to cyanide and anti-NR IgG and thereby proven to be different from PM-NR. Furthermore, PM-NR and NI-NOR were separated by gel-filtration chromatography and apparent molecular masses of 310 kDa for NI-NOR and 200 kDa for PM-NR were estimated. The PM-associated NI-NOR may reduce the apoplastic nitrite produced by PM-NR in vivo and may play a role in nitrate signalling via NO formation.
  Planta 03/2001; 212(5):835-841. · 3.00 Impact Factor
• Article: A succinate-oxidising nitrate reductase is located at the plasma membrane of plant roots

  Christine Stöhr, Wolfram R. Ullrich
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  ABSTRACT: Plasma-membrane-bound nitrate reductase (PM-NR) is located in roots and leaves of tobacco (Nicotiana tabacum L. cv. Samsun) and reduces nitrate with NADH as electron donor. When plasma membranes were prepared under specific protecting conditions, a PM-NR of roots was detected that accepts electrons from succinate to reduce nitrate. Comparison between the succinate dehydrogenase of mitochondria and the succinate-oxidising PM-NR of roots indicated that they are two different enzymes. Partial purification of the nitrate reductase forms by anion-exchange chromatography indicated that succinate and NADH supply electrons to the same plasma-membrane-bound protein.
  Planta 07/1997; 203(1):129-132. · 3.00 Impact Factor
• Source

  Available from: plantphysiol.org

  Article: Regulation by amino acids of photorespiratory ammonia and glycolate release from ankistrodesmus in the presence of methionine sulfoximine.

  M Larsson, C M Larsson, W R Ullrich
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  ABSTRACT: Methionine sulfoximine induced release of ammonia from illuminated cells of Ankistrodesmus braunii (Naegeli) Brunnth, in normal air, but less in air enriched to 3% CO(2). In normal air, methionine sulfoximine also induced glycolate release. Addition of either glutamate, glycine, or serine suppressed glycolate release, whereas glutamate and glycine at the same time stimulated ammonia release. The results indicate that inhibition of glutamine synthetase and thereby inhibition of photorespiratory nitrogen cycling restricts the sink capacity for glycolate in the photorespiratory carbon cycle. An external supply of glutamate, glycine, or serine seems to stimulate glyoxylate transamination and thus partly restores the sink capacity. Calculations of total glycolate formation rates in air from glycolate and ammonia release rates in the presence of methionine sulfoximine and glutamate revealed values of approximately 20 micromoles glycolate per milligram chlorophyll per hour on the average. Similar calculations led to an estimated rate of photorespiratory ammonia release in air, in the absence of methionine sulfoximine, of about 10 micromoles per milligram chlorophyll per hour on the average, a value comparable to the primary nitrogen assimilation rate of 8 micromoles per milligram chlorophyll per hour.
  Plant physiology 01/1983; 70(6):1637-40. · 6.53 Impact Factor
• Source

  Available from: plantphysiol.org

  Article: Effect of Glucose and CO(2) on Nitrate Uptake and Coupled OH Flux in Ankistrodesmus braunii.

  R Eisele, W R Ullrich
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  ABSTRACT: In Ankistrodesmus braunii, in the absence of CO(2), i.e. in CO(2)-free air or N(2), photosynthetic nitrate uptake and nitrate reduction were inhibited, especially at low pH. Under such conditions, glucose stimulated nitrate uptake and reduction to almost the same level in the pH range between 6 and 8.5. CO(2) at 0.03% effected an intermediate pH dependence of nitrate uptake; saturating CO(2) concentration (more than 1%) eliminated the pH dependence, as did glucose, but the rates were enhanced compared with glucose. Glucose and, even more, CO(2), drastically reduced the release of nitrite and ammonia to the medium, the stoichiometry between alkalinization of the medium and nitrate uptake (OH(-)/NO(3) (-)) approached 1.Due to the lack of storage vacuoles in Ankistrodesmus, nitrate uptake and nitrate reduction were closely coupled processes whose experimental separation is difficult. The relieving effect of glucose and CO(2) suggests a carrier-mediated nitrate uptake which is more limiting than nitrate reduction and is sensitive to low pH, but which is stabilized by some intermediate originating from an active carbon metabolism.
  Plant physiology 02/1977; 59(1):18-21. · 6.53 Impact Factor
• Article: Nitrate-dependent membrane potential changes and their induction in Lemna Gibba G 1

  Wolfram R. Ullrich, Anton Novacky
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  ABSTRACT: The electrical membrane potential (Em) of Lemna gibba cells was recordered during addition of nitrate. Transient nitrate-induced depolarisation in nitrogen-starved and induced plants was 55–70 mV in the dark, but only 20–30 mV in the light. Depolarisation was strongly enhanced by nitrate induction; it was pH-dependent and showed a saturation at 0:2 mM nitrate; it was iependent of K+. Plants with a low Em showed no depolarisation or even slight hyperpolarisation upon nitrate addition. The data suggest an H+/NO3− cotransport mechanism for nitrate uptake.
  Plant Science Letters 22(3):211-217.
• Article: Symbolism of plants: examples from European-Mediterranean culture presented with biology and history of art: NOVEMBER: Chicory

  Riklef Kandeler, Wolfram R Ullrich