ABSTRACT
Laboratory (bioassay), glasshouse and field experiments were set up in order to study allelopathic potential of two annual (Ambrosia artemisiifolia, Abutilon theophrasti) and two perennial (Cirsium arvense, Asclepias syriaca) weed species serious and widespread in Hungary. In bioassays, inhibitory effect on germination and radicle length of the test plants greatly depended on donor and recipient species, plant parts, extracts (water, ethanol and alcoholic ones) and the concentration of the extracts. In pot experiments under glasshouse conditions, water extract of A. theophrasti and C. arvense shoots, and roots residues of A. syriaca had a promoting effect on the development of crop plants. It could be due to utilization of nutrients from the plant extracts and residues and/or the microbiological degradation of phytotoxins in the soil. The opposite effect was observed in the case of shoot and root residues of A. theophrasti incorporated into the soil. It has been concluded that serious weeds, widespread in Hungary have allelopathic potential. Besides their resistance to some herbicides and considerable competitive ability, allelopathy must also be considered.
