Metabolism of Infiltrated Organic Acids by Tobacco Leaves

Abstract

Detached leaves of tobacco were vacuum infiltrated with solns. of C14-labeled formic, oxalic, glycolic, acetic, malic or citric acids adjusted to pH 5.5. After the leaves metabolized in the light or dark, their organic acids were recovered and analyyzed for C14. Formic acid apparently is a normal metabolite in tobacco leaves. It was converted rapidly to other organic acids and particularly high levels of C14 appeared in malic acid. Oxalic acid was rather inert in tobacco but was more active in buckwheat leaves. When labeled glycolic acid was metabolozed in the dark, the ratio of C14 in citric/malic acid was markedly higher than in the light. Both in light and dark much C14 from glycolic acid accumulated in oxalic acid. In the dark, acetic acid yielded citric acid of about twice the specific activity of malic acid. Acetic acid did not appear to be oxidized by way of glycolic acid. Malic acid was converted to citric acid by the darkened tobacco leaf. Citric acid was converted sluggishly to other organic acids.