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  • 1
    Electronic Resource
    Electronic Resource
    Adaptation and acclimation of higher plants at the enzyme level: Speed of acclimation for apparent energy of activation of NAD malate dehydrogenase in Lathyrus Japonicus Willd. (Leguminosae) (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 2 (1979), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The speed of acclimatory changes in apparent energy of activation (Ea) of NAD malate dehydrogenase was analysed in four clones of Lathyms japonicus Willd. collected over a 16° latitudinal gradient in eastern North America. Plants were grown initially for six months at either 7° night/15° day or 22° night/30° days. Following reciprocal switches in these two contrasting thermo-periods, energy of activation was relatively stable for 12 h, then oscillated until 48 h, and stabilized in about 72 h. The results suggest that the acclimation response in Ea is not due to near-instantaneous conformational changes in isozymes, but is directed primarily by temperature-mediated structural and/or functional modifications during de novo synthesis of the forms of the enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1979.tb00771.x
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  • 2
    Electronic Resource
    Electronic Resource
    Differences in thermal properties of NAD malate dehydrogenase in genotypes of Lathyrus japonicus Willd (Leguminosae) from maritime and continental sites (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 2 (1979), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The response of the kinetic properties of NAD malate dehydrogenase (MDH) was compared for two clones of Lathy rus japonicus Willd. collected in two contrasting climatic sites in Eastern North America. MDH from the cold adapted maritime genotype (Hudson Bay, Québec) had lower thermostability, reduced apparent (Ea) and free (ΔG†) energy of activation and lower specific activity when compared to MDH of plants from the warm summer continental site (Lake Michigan). Electrophoretic analyses show little differentiation in the isozyme profiles of the two genotypes. Thermostability differences were primarily associated with the mitochondrial isozymes which, however, were not differentiated electrophoretically Substrate binding ability of MDH, as measured by apparent Km, was more sensitive to high assay temperature in the cold adapted maritime genotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1979.tb00770.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of low temperatures on the activity of oxygen-scavenging enzymes in two populations of the C4 grass Echinochloa crus-galli (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 97 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To discriminate among possible mechanisms responsible for the differential response to cold temperatures among ecotypes of the C4 grass weed species Echinochloa crus-galli (L.) Beauv., the specific activities of five oxygen-scavenging enzymes responsible for the elimination or reduction of free radicals and hydrogen peroxide during cold-induced photoinhibition were determined in 5-week-old plants of two populations of the species collected from sites of contrasting climates, Québec (QUE) and Mississippi (MISS). Enzyme activities were measured at temperatures ranging from 5 to 30°C. The specific activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase were significantly higher in cold-adapted QUE plants at low assay temperatures than in warm-adapted MISS plants at the same temperature. The specific activities of superoxide dismutase assayed at 5 and 25°C were similar among plants of the two E. crus-galli populations. Ascorbate concentrations were not different among plants of the two populations, suggesting that the observed differences in the specific activities of ascorbate peroxidase assayed at 5°C, truly reflect a better capacity of the QUE enzyme to reduce H2O2 to water at temperature conditions associated with the photoinhibitory process. The enhanced specific activity of four of the five oxygen-scavenging enzymes measured in the cold-adapted QUE population at low assay temperatures correlates with the syndrome of cold-adapted features reported for plants of this population in earlier studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1996.970201.x
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal stability and kinetic properties of NADP+-malate dehydrogenase isomorphs in two populations of the C4 weed species Echinohloa crus-galli (Barnyard grass) from sites of contrasting climates (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The thermal stability and kinetic properties of purified NADP+-malate dehydrogenase (NADP+-MDH; EC 1.1.1.82) isomorphs were analyzed from plants of two populations of Barnyard grass from contrasting thermal environments. Plants from Québec (QUE) and Mississippi (MISS) were acclimated under controlled conditions at 26/20°C and 14/8°C (day/night). While the enzyme from QUE showed one isomorph, 3 isomorphs were detected in all plants from MISS, suggesting the presence of gene duplication and fixed heterozygosity for the expression of this dimeric enzyme. This findig raises the possibility that the enhanced acclimatory potential of NADP+-MDH from MISS plants, as found from previous studies with the partially purified and unfractioned enzyme, may result from differential kinetic properties of isomorphs which would allow for the proper modulation of catalysis over a wide temperature range. The thermal stability of the QUE isomorph was significantly higher than that of any of the MISS isomorphs. The apparent activation energy of the QUE isomorph was within the range of values found for the 3 MISS isomorphs which were similar to each other. The Michaelis-Menten constants (Km) for oxalacetic acid were not significantly different among isomorphs or between thermoperiods, but Km (NADP+) values for the QUE isomorph were significantly higher than those of two of the MISS isomorphs over the 15–25°C assay range Vmax/Km ratios for OAA and NADP+ were not significantly different among isomorphs or between thermoperiods. Our data indicate that, under highly purified conditions, the single NADP+-MDH isomorph of QUE plants possesses good acclimatory potential for maintaining catalytic efficiency under a wide range of temperature conditions. In vitro thermal and kinetic data do not support the hypothesis that the the multiple NADP+-MDH isomorphs found in MISS plants may have been selected to optimize the thermal and catalytic efficiency of NADP+-MDH under warm temperature conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb02145.x
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  • 5
    Electronic Resource
    Electronic Resource
    Differential effects of chilling on the activity of C4 enzymes in two ecotypes of Echinochloa crus-galli from sites of contrasting climates (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 69 (1987), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Five-week-old plants of Echinochloa crusgalli (L.) Beauv. from Mississippi and from Québec grown under controlled conditions were subjected to dark chilling for 10 h at 5°C or light chilling treatments for 14 h at 7°C under hight light (1 000 μmol m−2 s−1). The activities of four C4 enzymes of Québec plants, measured 4 h after the completion of the cold treatment, were not affected by the chilling treatment in the dark. The activities of pyruvate, Pi dikinase (PPDK; EC 2.7.9.1) and NADP+-malic enzyme (NADP+-ME; EC 1.1.1.40), were significantly reduced in dark-chilled Mississippi plants. Chilling under high light conditions elicited significant levels of reduction in the activities of the four enzymes from both ecotypes but the reductions were significantly less severe for Québec plants. The recovery of activities of phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) and PPDK for both ecotypes was completed within 36 to 60 hours following the chilling treatment, but NADP+-malate dehydro-genase (NADP+-MDH; EC 1.1.1.82) and NADP+-ME activities of chilled Mississippi plants remained below that of control plants at the end of the 5-day monitoring period. PPDK was inactivated in vitro at 0 and 10°C and the rates of cold inactivation were significantly higher for PPDK extracted from Mississippi plants. The activity of PEPC of Mississippi extracts was slightly, but significantly reduced by a 60 min treatment at 0°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb04277.x
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  • 6
    Electronic Resource
    Electronic Resource
    Adaptation and acclimation of higher plants at the enzyme level: Latitudinal variations of thermal properties of NAD malate dehydrogenase in Lathyrus japonicus Willd. (Leguminosae) (1979)
    Springer
    Oecologia 39 (1979), S. 273-287 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thermal properties of NAD malate dehydrogenase were investigated in 8 clonal populations of Lathyrus japonicus Willd. collected over a 16° latitudinal gradient in eastern North America. Clones from warmer summer sites had higher activation energies (E a) and enhanced thermostability for the enzyme under three contrasting growth temperature regimes. A strong component of acclimation was associated with E a, but not with thermostability. Activity levels of the enzyme were higher in warm-adapted genotypes but cold-acclimated plants had similar low levels of specific activity. The clones were differentiated by ordination in a pattern related to climatic origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00345439
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal adaptation and acclimation of higher plants at the enzyme level: kinetic properties of NAD malate dehydrogenase and glutamate oxaloacetate transaminase in two genotypes of Arabidopsis thaliana (Brassicaceae) (1983)
    Springer
    Oecologia 60 (1983), S. 143-148 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Kinetic properties of NAD malate dehydrogenase (MDH) and glutamate oxaloacetate transaminase (GOT) were analyzed in two genotypes of Arabidopsis thaliana collected in two sites of contrasting climates. Plants from each genotype were acclimated under controlled conditions at four different thermoperiods: 5–10° C, 7–15° C, 15–25° C and 25–28° C. Apparent energy of activation for MDH of the cold adapted genotype were significantly lower at low temperatures of acclimation, while for GOT, significant differences were found but no clear patterns emerge from the data. No differences of significance between the two genotypes were observed for apparent K m and K cat of both enzymes. For MDH, apparent K ms for oxaloacetic acid increased as a positive function of assay temperature but for GOT, K ms for α-oxoglutaric acid did not vary significantly over the 10–35° C assay temperature range. K cat values for both enzymes increased about 2 fold for every 10° C raise in assay temperature. Concentrations of both enzymes significantly increased in plants of both genotypes acclimated to the coldest thermoperiod. The concentration of GOT was signficantly higher in plants of the cold adapted genotype acclimated to 5–10° C and 7–15° C. Results suggest that MDH and GOT from the cold adapted genotype are more efficient in the modulation of catalysis at low temperatures, while the opposite is found for plants of the warm-adapted genotype through enhanced thermostability of the mitochondrial fraction of MDH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379515
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of low temperature on the photosynthetic metabolism of the C4 grass Echinochloa crus-galli (1986)
    Springer
    Oecologia 69 (1986), S. 499-506 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary CO2 curves of photosynthesis and activities of the four C4 enzymes and Ribulose bisphosphate carboxylase (RUBPc) were compared in two populations of the C4 grass Echinochloa crus-galli from contrasting thermal environments (Québec and Mississippi). Analyses were conducted both before and after 14 h of chilling at 7°C under high light conditions. This comparison provides the opportunity to assess which steps of the C4 pathway are more susceptible to become limiting at low temperatures. Both populations maintained, after chilling, a pattern of CO2 fixation typical of C4 plants with photosynthesis saturating at low external CO2 concentrations. However, the chilling treatment led to reductions in carbon uptake and in the activities of the C4 enzymes. RUBPc activity was not significantly affected by chilling. Reductions in photosynthesis and in C4 enzyme activities following the chilling treatment were significantly larger for plants of the Mississippi population. The enzyme data suggest that two steps of the C4 pathway, NADP+-malate dehydrogenase and pyruvate Pi dikinase, are likely to be associated with the reduction of CO2 uptake in C4 plants under cool conditions. When the experiment was replicated under enriched atmospheric CO2 (675 μl l-1 CO2), similar differences were observed between the two populations. CO2 enrichment resulted in an increase of activity for phospho-enol-pyruvate carboxylase and NADP+-malate dehydrogenase while activities of phospho-enol-pyruvate carboxylase and NADP+-malic enzyme were less reduced following chilling. Such an interaction was not observed for gas exchange parameters but net photosynthesis was lower when plants were grown under enriched CO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00410354
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of temperature and CO2 enrichment on kinetic properties of phospho-enol-pyruvate carboxylase in two ecotypes of Echinochloa crus-galli (L.) Beauv., a C4 weed grass species (1984)
    Springer
    Oecologia 63 (1984), S. 145-152 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two populations of Echinochloa crus-galli (Québec, Mississippi) were grown at the Duke University Phytotron under 2 thermoperiods (28°/22°C, 21°/15°C day/night) and 2 CO2 regimes (350 and 675 μl l-1). Thermostability, energy of activation (E a ),K m (PEP), K m (Mg++), and specific activity of phospho-enol-pyruvate carboxylase (PEPc) were analyzed in partially purified enzyme preparations of plants grown for 5 weeks. Thermostability of PEPc from extracts (in vitro) and leaves (in situ) was significantly higher in Mississippi plants. In vitro denaturation was not appreciably modified by thermal acclimation but CO2 enrichment elicited higher thermostability of PEPc. In situ thermostability was significantly higher than that of in vitro assays and was higher in Mississippi plants acclimated at 28°/22°C and in plants of the two ecotypes grown at 675 μl l-1 CO2. E a (Q 10 30°/20°C) for PEPc was significantly lower in Québec plants as compared to Mississippi and no acclimatory shifts were observed. Significantly higher K m's (PEP) in 20°C assays were obtained for Mississippi as compared to Québec plants but values were similar at 30°C and 40°C assays. K m (Mg++) decreased at higher assay temperatures and were significantly lower for PEPc of the Québec ecotype. No significant changes in K m (Mg++) values were associated with modifications in temperature on CO2 regimes. PEPc activity measured at 30°C was significantly higher for Québec plants when measured on a leaf fresh weight, leaf area or protein basis but not on a chlorophyll basis. Significantly higher PEPc activity for both genotypes was observed for plants acclimated at 21°/15°C or grown at 675 μl l-1 CO2. Net photosynthesis (Ps) and net assimilation rates (NAR) were higher in Québec plants and were enhanced by CO2 enrichment. NAR was higher in plants acclimated at low temperature, while an opposite trend was observed for Ps. PEPc activities were always in excess of the amounts required to support observed rates of CO2 assimilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379870
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of temperature and CO2 enrichment on kinetic properties of NADP+-malate dehydrogenase in two ecotypes of Barnyard grass (Echinochloa crus-galli (L.) Beauv.) from contrasting climates (1989)
    Springer
    Oecologia 81 (1989), S. 138-144 
    Details
    ISSN: 1432-1939
    Keywords: Echinochloa crus-galli ; Ecotypes ; Temperature ; CO2 enrichment ; C4 metabolism ; NADP+-malate dehydrogenase ; Energy of activation ; K m, V max/K m
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The apparent energy of activation (E a), Michaelis-Menten constant (K mfor oxaloacetate), V max/K mratios and specific activities of NADP+-malate dehydrogenase (NADP+-MDH; EC 1.1.1.82) were analyzed in plants of Barnyard grass from Québec (QUE) and Mississippi (MISS) acclimated to two thermoperiods 28/22°C, 21/15°C, and grown under two CO2 concentrations, 350 μl l-1 and 675 μl l-1. E avalues of NADP+-MDH extracted from QUE plants were significantly lower than those of MISS plants. K mvalues and V max/K mratios of the enzyme from both ecotypes were similar over the range of 10–30°C but reduced V max/K mratios were found for the enzyme of QUE plants at 30 and 40°C assays. MISS plants had higher enzyme activities when measured on a chlorophyll basis but this trend was reversed when activities were expressed per fresh weight leaf or per leaf surface area. Activities were significantly higher in plants of both populations acclimated to 22/28°C. CO2 enrichment did not modify appreciably the catalytic properties of NADP+-MDH and did not have a compensatory effect upon catalysis or enzyme activity under cool acclimatory conditions. NADP+-MDH activities were always in excess of the amount required to support observed rates of CO2 assimilation and these two parameters were significantly correlated. The enhanced photosynthetic performance of QUE plants under cold temperature conditions, as compared to that of MISS plants, cannot be attributed to kinetic differences of NADP+-malate dehydrogenase among these ecotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377023
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