Autotoxicity of barley

Allelopathic potential of a crop species varies depending on stage of growth. Because allelopathy of barley (Hordeum vulgare L.), an important cereal grain adapted to semi-arid conditions of northern Tunisia, has not been widely reported, a study was conducted to determine i) the potential autotoxicity of barley and ii) the differential allelopathic potential of barley plant components over four phenological stages. The study involved experiments with barley seed germination and seedling growth bioassay techniques for detection of allelopathic activity. Plant parts of field-grown 'Rihane' barley were extracted with distilled water. At growth stage 4 (stems not well developed), whole plants were extracted. Thereafter, roots, stems, and leaves were extracted separately. Water extracts of 'Rihane' barley plant parts were bioassayed on four varieties of barley. Seedling growth bioassays revealed autotoxicity of barley, which appeared to be more pronounced on radicle growth than coleoptile growth, especially when plants near physiological maturity were extracted. Autotoxicity was not significant when 'Rihane' barley was simultaneously the donor and recipient of water extracts. Leaves were the most important source of allelopathic substances. Root extracts were least inhibitory toward both radicle and coleoptile growth. Results suggest qualitative and quantitative changes in allelopathic substances in barley plant parts during plant development.