Phenolic compounds and phenylalanine ammonia lyase activity in relation to phytoalexin biosynthesis in infected hypocotyls of Phaseolus vulgaris

• Published in: Physiological plant pathology Vol. 3; no. 2; pp. 259 - 267
• Main Author: Rathmell, W.G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.1973
• ISSN: 0048-4059
• DOI: 10.1016/0048-4059(73)90088-X

The levels of the phenolic compounds that are present in healthy hypocotyls of Phaseolus vulgaris, namely flavonol glycosides, leucoanthocyanins and hydroxycinnamic acids, are not appreciably affected when the hypocotyls are infected with a compatible race of Colletotrichum lindemuthianum. Infection causes the production of new compounds including the isoflavonoids phaseollin and coumestrol; the changes that take place are spatially and temporally closely associated with the formation of necrotic lesions. It is suggested that the phenolic compounds of the healthy hypocotyl may be synthesized in different cells from those that produce new compounds during infection. Evidence is presented that the increase in the amount of the enzyme phenylalanine ammonia lyase that is observed during infection takes place about 24 h earlier than either lesion formation or changes in the concentration of phenolic material. Changes in enzyme concentration that are concerned with the changes in phenol metabolism may thus take place in cells before they become necrotic.