SummaryIn the present study, the allelopathic effects of Zygophyllum simplex aqueous extract on Vicia faba was tested. Three concentrations (10, 20 and 40%) for three times of treatment (6, 12, 18 h) were applied. The control plants were normal, while the treated ones were significantly affected. Low concentration (10%) at all treatment times had a stimulatory effect on seed germination percentage. On the other hand, high concentration of the extract gave rise to substantial reduction in all parameters studied as the concentration increase and time of treatment prolonged. In contrast, the percentage of mitotic and meiotic aberrations increased and were time and dose dependent. Various types of mitotic and meiotic aberrations were observed. Sticky and micronuclei types of aberrations were found more frequently, confirming the toxic effect of the extract at high concentrations. Meiotic parameters of chromosome association, chiasma frequency and pollen fertility were also found affected by the time and dose. The present study proves the mutagenic effects of this extract on Vicia faba, especially at high doses. It also recommends its use at low concentrations when used as folk medicine. However, with the use of medicinal plants for treatment (folk medicine) recently increasing instead of synthetic chemical drugs, their side effects and safe and effective dose should be carefully pretested and documented before public use.