Suspension-cultured cells were used to analyze the activation of defense responses in the conifer A. angustifolia, using as an elicitor purified chitosan polymers of different degrees of acetylation (DA 1-69%), chitin oligomers of different degrees of polymerization (DP 3-6), and chitosan oligomer of different DA (0-91%). Suspension cultured cells elicited with chitosan polymers reacted with a rapid and transient generation of H2O2, with chitosans of high DA (60 and 69%) being the most active ones. Chitosan oligomers of high DA (78 and 91%) induced substantial levels of H2O2, but fully acetylated chitin oligomers did not. When cultivated for 24-72 h in the presence of 1-10 mu g mL(-1) chitosan (DA 69%), cell cultures did not show alterations in the levels of enzymes related to defense responses, suggesting that, in A. angustifolia, the induction of an oxidative burst is not directly coupled to the induction of other defense reactions.