[Cinnamic acid 4-hydroxylase and 0-methyltransferase activities in leaves of hypersensitive tobacco plants infected by tobacco mosaic virus].

Tobacco leaves of Nicotiana tabacum L., variety Samsun NN, show a low cinnamic acid-4-hydroxylase activity and a rather high O-methyltransferase activity. Caffeic acid, the substrate of the latter enzyme, is methylated specifically in the meta position. In TMV-infected leaves a strong increase in the activities of phenylalanine ammonia-lyase and of these two enzymes occurs at the time of appearance and development of the necrotic reaction.