Abstract , Allgem eine Botanik und Pflanzenphysiologie, Auf der Morgenstelle Suspension cultured cells of an anthocyanin-containing cell line (DCb) from Daucus carota L. ssp. sativus respond very rapidly to treatment with a soluble carbohydrate elicitor from the wall of the oom ycete Pythium aphanidermatum by synthesizing 4-hydroxybenzoic acid which is incorpo rated into the plant cell wall. Enzym es of phenol m etabolism , phenylalanine am m onia-lyase (P A L) and chalcone synthase (C H S), respond to elicitor treatment in different ways. Both the catalytic activity of PAL and its subunit concentration, measured by means of immunoblotting, show a transient increase upon elicitation, whereas CHS the initial enzyme of the flavonoid pathway, is inhibited after administration of the elicitor. and consequently anthocyanin accum ula tion ceases. In protoplasts derived from the cultured cells a very similar elicitor-induced response has been observed. Lacking a cell wall, the protoplasts secrete the 4-hydroxybenzoic acid into the culture fluid. The carrot protoplasts isolated by wall degrading enzym es retain their responsive ness to the fungal carbohydrate elicitor. The value of the protoplast system for studying the im m ediate events following elicitor treatment is discussed.