STUDIES OF LIGNIN BIOSYNTHESIS USING ISOTOPIC CARBON: I. LONG-TERM EXPERIMENT WITH C¹⁴O₂

Abstract

Wheat plants were fed with C 14 O 2 at the stage of growth corresponding to rapid lignification. Thereafter, plants were harvested every few days until maturity. The specific and total activity of the plants, and the specific and total activity in some lignin degradation products were determined. Results indicated that (i) C 14 O 2 was still being respired from the plants at maturity, (ii) all the C 14 which gets into the lignin does so within 24 hr. from the administering of C 14 O 2 , (iii) the total activity originally acquired by the syringaldehyde portion of the lignin remains constant throughout the growth of the plant, that is, the lignin (as represented by syringaldehyde) is a final end product of the plant and is not a part of the respiratory system, (iv) the total activity originally acquired by the vanillin suffers an initial drop for about two weeks after activation and then becomes constant, (v) the p-hydroxybenzaldehyde activity drops continuously throughout the life of the plant.