Ferulic acid is bound to the primary cell walls of all gymnosperm families

Unlignified primary cell walls containing ester-linked ferulic acid fluores ce blue in ultraviolet radiation which changes to green with increased inte nsity on treatment with ammonium hydroxide. Using this fluorescence behavio ur, we detected ester-linked ferulic acid in the primary cell walls of all 41 species of gymnosperms we examined. These species were in 17 families re presenting all four extant classes of gymnosperms. In addition, we obtained cell-wall preparations containing > 95% primary cell walls from nine gymno sperm species in nine families, representing all four extant classes. These preparations were analysed for ester-linked monomeric phenolic acids. We f ound ferulic acid (mostly trans) (88-1,561 mu g/g cell walls) in all of the preparations and p-coumaric acid (mostly trans) (0-106 mu g/g cell walls) in all except one of them. Ferulic acid eater-linked to primary cell walls has previously been found in angiosperms: in the commelinoid monocotyledons and in the dicotyledon order Caryophyllales, both monophyletic groups. Fro m the present results, we postulate that the extant classes of gymnosperms are monophyletic and no class is sister to the angiosperms. (C) 2000 Elsevi er Science Ltd. All rights reserved.