Induction of Browning of Male Flowers of Cryptomeria japonica by Treatment with Fatty Acids: Mechanism and the Role of trans-2-Hexenal

The effect of treatment with fatty acids on the browning ofmale flowers of Cryptomeria japonica and its mechanism werestudied with emphasis on the role of trans-2-hexenal. The effectof treatment with fatty acids on the browning of male flowerswas the highest when fatty acids were applied at the end ofAugust, decreasing month by month thereafter in parallel withthe seasonal changes in lipoxygenase activity. trans-2-Hexenal,which is formed from linolenic acid in a reaction catalyzedby lipoxygenase (EC 1.13.1.13[EC]), stimulated the evolution ofethylene and acetaldehyde in male flowers predominantly, withresultant enhancement of the activity of phenylalanine ammonia-lyase(EC 4.3.1.5[EC]), and the browning of male flowers. A possible biochemicalpathway for browning of male flowers of Cryptomeria japonicais discussed. (Received September 19, 1994; Accepted September 7, 1995)