MODULATOR EFFECT OF DL-ALPHA-DIFLUOROMETHYLARGININE TREATMENTS ON DIFFERENTIATION PROCESSES OF YOUNG MAIZE CALLUSES

The effect of pretreatments with 0.5, 1, 3, 5 and 10 mM of DL-alpha-di fluoromethylarginine (DFMA), an irreversible suicide inhibitor of the arginine decarboxylase (ADC) activity, on the differentiation process of young maize calluses was studied. Callus protein, total polyamine c ontent and ADC activity decreased versus control in all the assayed tr eatments. Furthermore, ornithine decarboxylase (ODC) activity was sign ificantly lower in the treated calluses, which was probably due to the arginase activity detected in them. Short tratments at high doses of DFMA significantly increased the number of regenerated buds versus the control (four times more in 10 mM and almost two times more in 5 mM). By contrast, long treatments at low doses (0.5, 1 and 3 mM) reduced t he number of plantlets. Conjugated putrescine seems to be implicated i n the regeneration response of control and high DFMA-treated calluses.