The Nature of Induced Lignin in Carrot (Daucus carota L.) Callus Cells Elicited with Hot Water Extracts from Conidia of Botrytis cinerea

Carrot callus cells showed a positive reaction to phloroglucinol-HCl after eliciting with hot-water extract from conidia of Botrytis cinerea. The positive reaction reflected increases in the content of thioglycolic acid lignin and in the activity of phenylalanine ammonia-lyase. Alkaline nitrobenzene oxidation of thioglycolic acid lignin eliminated both ρ-hydroxybenzoic acid and vanillin. The amount of ρ-hydroxybenzoic acid increased after eliciting with hot-water extract of conidia, but the amount of vanillin did not increase. The only phenolic substance liberated from thioglycolic acid lignin by alkaline hydrolysis was ρ-hydroxybenzoic acid and the amount was also increased by elicitation. The phenolic substances in dioxane lignin were ρ-hydroxybenzoic acid, vanillin, vanillic acid, and syringaldehyde, but only the amount of ρ-hydroxybenzoic acid was increased after elicitation. Phenolic substances liberated from cell wall materials by alkaline hydrolysis were predominantly ρ-hydroxybenzoic acid; ρ-hydroxybenzoic acid in particular increased in cell wall materials from cells elicited. The increased ρ-hydroxybenzoic acid formed ester-bonds via its hydroxyl and carboxy groups to cell wall materials. Induced lignification in cultured carrot callus cells indicated an increase of ester-bonded ρ-hydroxybenzoic acid in lignin precursor or wall polysaccharides rather than de novo synthesis of lignin.