100 research outputs found
Efecto del glifosato sobre el crecimiento y acumulación de azúcares libres en dos biotipos de lolium perenne de distinta sensibilidad al herbicida
Species variation in the predawn inhibition of ribulose-1,5-biphosphate carboxylase/oxygenase.
Species Variation in the Predawn Inhibition of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase
The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase was measured in extracts of leaves collected before dawn (predawn activity, pa) and at midday (midday activity, ma). Twenty-three of the 37 species examined showed a pa/ma ratio (≤0.75, while only Capsicum frutescens, Cucumis sativa, Glycine max, Nicotiana tabacum, Vigna unguiculata, and 3 Solanum species showed a pa/ma ratio ≤0.5. Phaseolus vulgaris consistently showed a pa/ma ratio of ≤0.1. Activities and pa/ma ratios of the same species grown in the United States and the United Kingdom were very similar. Gel filtration of extracts before assay had no effect on the observed activities and the pa/ma ratios. These data are consistent with the hypothesis that in a number of species the enzyme is partially inhibited following the night period by the presence of a tight-binding inhibitor
Species Variation in the Predawn Inhibition of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase
Regulation of Rubisco by inhibitors in the light
2-carboxy-D-arabinitol-1-phosphate (CA1P) bound to Rubisco either in leaf extracts or after purification can be displaced by SO42- ions. Thus, treatment of leaf extracts with a buffer containing 200 mol m-3 SO42- displaces any bound CA1P and enables measurement of maximum carboxylation potential. In tobacco leaves, the activity following treatment with SO42- ions ('maximal activity') is greater than the total Rubisco activity. The ratio of the two activities altered in a dynamic way with fluctuations in irradiance. Even in species which do not produce significant amounts of CA1P, the maximal activity greatly exceeded the total activity. Anion exchange separation of components in acid extracts confirmed the absence of CA1P in tobacco leaves harvested above an irradiance of 300 μmol quanta m-2 s-1, but the presence of another inhibitor of Rubisco. These results are consistent with the regulation of Rubisco activity by inhibitors other than CA1P which, like CA1P, can be displaced by SO42-ions
Photoinhibition and Recovery in Isolated Mesophyll Cells of Hardened and Non-Hardened Rye
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