The Role of Shikimic Acid in Waterlogged Roots and Rhizomes ofIris pseudacorusL.

Levels of shikimic acid in the roots and rhizomes of Iris pseudacorus growing under natural conditions were measured at monthly intervals for a period of one year. Seasonal fluctuations in the shikimate content suggest that the high levels during winter flooding and lower levels during the summer period of low water table are related to a particular flood-tolerance metabolism in the roots and rhizomes. The suggested pathway, involving the condensation of phosphoenolpyruvate and crythrose 4-phosphato (both formed during anaerobic carbohydrate breakdown) to 3-deoxy-D-arabino-heptulosouic acid 7-phosphate and the subsequent synthesis of shikimie acid, appears to function as a physiological adaptation to flooding in rhizomatous species such as I. pseuducorus. Other pathways of anaerobic respiration in waterlogged roots are discussed in relation to the proposed scheme in Iris.