Phenolic metabolism in petunia tissues. I. Characteristic responses of enzymes involved in different steps of polyphenol synthesis to different hormonal influences.

Pronounced changes in enzymatic patterns occur in petunia tissues when calluses are subcultured on media containing different growth substances. As judged by variations of enzymes related to primary metabolism (6-phosphogluconate and malate dehydrogenases) there are individual responses for each metabolic pathway. Concerning the enzymes of aromatic metabolism: (a) Phenylalanine ammonia-lyase, cinnamate and p-coumarate hydroxylases and the enzyme(s) activating phenylpropanoid units vary in the same manner. (b) Chalcone-flavanone isomerase, a key enzyme in the synthesis of flavonoids, and coniferyl alcohol dehydrogenase, which leads to the monomers of lignins, have, on the other hand, an independent behaviour. These responses show that the enzymes involved in the synthesis and activation of phenylpropanoid units seem to act coordinately in plants. Moreover, the data suggest that the common pathway leading to the activated cinnamic acids and the specific metabolic steps of lignin and flavonoid synthesis are regulated in a different way.