The paper tested the effect of ultrasound of output density of 0.1 W/cm3 (stable frequency, 35 kHz) on the production of flavonoids in the suspension culture of Ononis arvensis L. The use of this abiotic elicitor was proved good to increase the production of secondary substances (flavonoids) in the culture of Ononis arvensis L. in vitro. The maximal production of flavonoids began after a 1 min action of ultrasound and immediate withdrawal of the culture – an increase by 677 % in comparison with the control (without the action of ultrasound).

        Key words: Ononis arvensis L. – suspension culture – flavonoids – ultrasound