Cell wall bound‐phenols in roots of vesicular‐arbuscular mycorrhizal plants

summary This paper examines the qualitative and quantitative chemical composition of phenols occurring in the cell wall of vesicular‐arhuscular (YA) mycorrhizal and non‐mycorrhizal roots of Allium porrum L. and Ginkgo bilnba L. their localization at the cellular level, and the phenylalanine ammonia lyase (PAL) activity of these tissues. Constitutive phenols occurred in both species of plants, and did not change when the symbiont Cully colonized the roots. Cell wall bouncl‐phenols were more abundant in A. porrum than in C. biloba , and PAL activity was higher too. Tyrosol, 2‐(4‐hydroxyphenyl ethanol), was identified as the most abundant component in A. porrum , where it occurred with vanillic, syringic and ferulic acids. In G. biloba , p‐coumaric, protocathecuic, vanillic and ferulic acids were found. Cell‐wall bound phenols (revealed by UV fluorescence and by transmission electron microscopy) were localized in the epidermal and hypodermal cells, but did not usually occur in the cortical cells, where the fungus developed arbuscules. We show that cell wall bound‐phenols are constitutive compounds in leek and in ginkgo:, and that the VA mycorrhizal fungus does not activate metabolic pathways leading to the synthesis of new phenols as antimicrobial substances, at least in the host cell walls.