Reduction of phenolics in mycorrhizas of Larix decidua Mill.

Soluble and cell-wall-bound phenolics in mycorrhizas of Larix decidua-Laccaria amethystea and in nonmycorrhizal fine roots of larch grown in sterile culture were analyzed by HPLC. The soluble phenolics p-hydroxybenzoylglucose, p-hydroxybenzoic acid glucoside, picein, catechin, and epicatechin were identified in nonmycorrhizal fine roots. The same phenolics also occurred in mycorrhizas, but only in very small quantities compared with those in nonmycorrhizal fine roots. The amount of cell-wall-bound ferulic acid was much lower in mycorrhizas than in nonmycorrhizal fine roots. Pure mycelia of Laccaria amethystea (Bull.) Murr. contained none of the identified phenolics. We conclude that L. amethystea induced a large decrease in soluble and cell-wall-bound phenolics in fine roots of Larix decidua Mill. that may explain their rapid mycorrhization.