Barley and rape seedlings were grown in hydroponic culture with increasing concentrations of CrO3 (Cr(VI)) or CrCl3 (Cr(III)). The chitinase activity and the concentrations of putrescine, spennidine and spermine were determined in the third leaf of barley seed-lings and in the second leaf of rape seedlings. With increasing concentrations of Cr(VI) (30-100-mu-g/l) a 5-10-fold increase in chitinase activity and 4-5-fold increase in putrescine concentration were found in barley and rape seedlings after 4 days. Levels of spermidine and spermine were not consistently influenced by exposure to Cr(VI). Cr(III) at concentrations of 10-50-mu-g/ml did not significantly alter the concentrations of polyamines nor the chitinase activities in either species, however, at 100-mu-g/ml in barley Cr(III) induced an increase in putrescine concentration after 6 days of exposure. The induction of chitinases and the increases in the putrescine level caused by Cr(VI) but not by Cr(III) (10-50-mu-g/ml) exposure is similar in the two species suggesting an analogous defense system in both mono- and di-cotyledonous plants. The anionic form of Cr(VI) seems to be more potent than the cationic form of Cr(III). Grain of barley plants grown in enriched peat and watered with increasing concentrations of Cr(VI) (250, 1250, 6250 or 10 000-mu-g/ml) for 4 days from 10 days post anthesis (dpa) showed increasing contents of chitinases.