Extracellular plant β-galactosidase from opium poppy and celandine was detected on agar plates by the presence of dyed zones from 1-naphthyl-β-D-galactopyranoside used as a synthetic substrate. Evaluating the azo-dye zones assessed the degree β-galactosidase activity. No coloration of the agar medium was observed on non-inoculated parts, in medium inoculated with heat – inactivated cells (10 min. at 100oC) or in medium without substrate with all calli tested. On the agar plates with substrate and sterile opium poppy, celandine or gherkin seedlings (2–6 days old) changes in coloration were observed showing the release of β-galactosidase from the roots during germination.