A High Concentration of Glucogallin, the Common Precursor of Hydrolyzable Tannins, Does Not Deter Herbivores

The diversity of structures of plant phenolic compounds suggests that their interactions with insect herbivores may be compound specific. In this study, we modified the natural covariances observed in mature leaves of mountain birch, Betula pubescens ssp. czerepanovii (Orlova) Hamet-Ahti, by supplying gallic acid, the common precursor of gallotannins, through the stems of cut branches. Only one gallotannin, glucogallin, was consequently increased, and responses to this change on larvae of Epirrita autumnata Bkh. were evaluated by choice and nonchoice experiments. Glucogallin-increased leaves were consumed equally to control leaves in a nonchoice situation and they were preferred by E. autumnata larvae when they had to choose. No other short-term postingestive effects in E. autumnata larvae were observed and therefore our studies did not suggest a defensive role for glucogallin.