Allelopathy Journal

The effects of Malva sylvestris and Sisymbrium irio on wheat and barley were used to model the differences in the observed effects of plant species in the field, laboratory and glasshouse experiments. Observations on the effects of two weed species on same crops in field differed from their effects under laboratory or glasshouse conditions. The differences were similar between the laboratory and glasshouse experiments. Results showed the risk, in depending on single experimental technique to explain and determine the type of interference between the plant species in nature. The observed inhibitory zone of certain species in nature may not be always due to allelopathic effects, while strong inhibitory effects of extracts of certain species observed in laboratory experiments may not be achievable in glasshouse pot experiments and opposite responses are possible. Tendency of both weed species to form pure colonies in the field, as difficult to confirm in terms of allelopathic effects in pot experiments (under glasshouse conditions). Similar differences were obtained in the effect of two weed species on both crops between laboratory and glasshouse experiments. It is concluded that the effects of plant extracts in laboratory experiments may not confirm the allelopathy influence and plants interactions lead to exclusion of certain species from spots in the field, which were observed as inhibitory zones may be due to different plant interactions mechanism/s other than allelopathy.