Factors Controlling the Synthesis of Natural and Induced Lignins in Phleum and Elodea

Abstract

Since Elodea densa accumulates significant amounts of flavonoids and alkali-sensi-tive esters of hydroxycinnamic acids, and excised tissues produce lignin-like compounds only in the presence of added hydroxycinnamic acids and H2O2, the block to lignification may lie in the pathway of the production or utilization of H2O2. There was no complete block to lignification in tissues of Phleum pratense, but none of the intact tissues attained the maximum lignification that could be induced in the presence of excess hydroxycinnamic acids and H2O2. In excised tissues incubated with sucrose, the major limiting factor appeared to be some step between the level of sucrose and ferulic acid. Activities of peroxidase, polyphenoloxidase and ascorbic acid oxidase were similar in Elodea and Phleum. While IAA at a concentration of 10-4 [image] inhibited the pro-duction of lignin in excised tissues of the 1st internode of Phleum when incubated with sucrose, there was no detectable effect of kinetin or gibberellin singly or in combination with IAA. Two possible interrelated mechanisms controlling lignification in intact tissues of Phleum are discussed; 1 is the level of caffeic acid esters, the other is the level of IAA.