Effect of low temperatures on the activity of oxygen-scavenging enzymes in two populations of the C4 grass Echinochloa crus-galli |
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Authors: | Nadia Hakam Jean-Pierre Simon T. C. Vogelmann |
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Affiliation: | N. Hakam and J.-P. Simon (corresponding author, fax 1–514–3432293), Dépt de sciences biologiques, Univ. de Montréal. C.P. 6128. succursale centre ville, Montréal. PQ, H3C 3J7, Canada;. |
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Abstract: | 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. |
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Keywords: | Ascorbate peroxidase barnyard grass cold-induced photoinhibition dehydroascorbate reductase Echinochloa crus-galli ecotypes glutathione reductase monodehydroascorbate reductase superoxide dismutase |
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