Enhancement of CO2 Uptake in Avena Coleoptiles by Fusicoccin

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Abstract
When Avena coleoptile segments are immersed in a solution containing H14CO3−, the appearance of label in the tissue is stimulated approximately 3-fold by fusicoccin application. This effect is rapid (1-2 minutes lag time), dependent upon respiratory energy, inhibited by carbonyl cyanide m-chlorophenylhydrazone, but not appreciably altered by cycloheximide treatment. A large percentage of the cellular radioactivity is found in the form of malate. Preliminary experiments indicate that CO2, as opposed to HCO3−, is the favored species of “CO2” taken up by the segments. These results are consistent with the notion that CO2, presumably by virtue of its fixation and conversion to malic acid, participates in the early events associated with fusicoccin-enhanced acidification of the cell wall region leading to the stimulation of cell extension growth.