Metabolism of Isolated Leaves: I. Changes in the Protein, Soluble Nitrogenous Compounds, Sugars, and Organic Acids in Tobacco Leaves in Light and Dark

Abstract

Evidence is presented that although the total amino N content increases both in light and in dark in detached leaves, the behavior of individual amino acids and amide varies considerably. It has been shown that nutritional factors regulate the accumulation of glutamine in isolated leaves in light and dark and that pathway of interconversion between glutamine and proline are regulated by these factors also. Nicotiana tabacum var. S-20 leaves failed to show any malic-citric conversion of the type reported for Connecticut tobacco by Vickery et al which the cheroot variety leaves carried out in dark. Cheroot variety, however failed to do so when cultured on a mixture of streptomycin and penicillin solution. Culture of S-20 variety leaves in antibiotic solution did not result in any alteration of the behavior of organic acids. Feeding experiments have shown that the enzymes of the regular citric acid cycle are operative in this variety. It is suggested that the peculiar behavior of organic acids in certain variety of tabacco leaves is due to the operation of enzyme systems other than those encountered in the Krebs citric acid cycle, probably malic enzyme, and that this is blocked in the presence of antibiotics.