Photorespiration and malate formation in grape leaves [Vitis]
1981
Malipiero, U. | Ruffner, H.P. | Rast, D.M. (Zurich Univ. (Switzerland). Inst. fuer Pflanzenbiologie)
Excised grape leaves were fed (14) carbon dioxide (CO2) in a closed assimilation chamber for 10 and 30 min, respectively, and the incorporation of radioactive label into the watersoluble substances was determined. Under the experimental conditions glycine/serine and sucrose constituted the main radioactive pools, whilst only traces of label were detectable in glycolate. However, administration of glycolate oxidase inhibitors (alpha-hydroxypyridinemethansulfonic acid or glyoxel sodium bisulfite) through the leaf petiole prior to (14) CO2 labelling led to an accumulation of (14) carbon-glycolate, thus indicating that in grape leaves a considerable portion of fixed carbon is normally metabolized via the photorespiratory pathway. Environmental conditions which favour photorespiration caused enhanced incorporation of 14(CO2) not only into glycolate pathway intermediates but also into glycerate and malate. This finding suggests a close precursor-product relationship between the relevant photorespiratory compounds on the one hand and glycolytic carbon (3)-compounds and malic acid on the other.
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