Submitted to: International Allelopathy Congress
Publication Type: Proceedings
Publication Acceptance Date: 8/12/1999
Publication Date: N/A
Technical Abstract: Allelopathic potential of a crop species varies depending on stage of growth. Since allelopathy of barley (Hordeum vulgare) is understudied, a barley variety ('Rihane')commonly grown in the semi-arid zone of Tunisia was selected to i) determine the form of phytotoxicity of barley, ii) identify the most allelopathic plant part, and iii) define the change of their respective allelopathic potentials over four growth stages following the Feekes scale. An experiment using germination and seedling growth bioassay techniques was conducted. Plant parts were extracted with distilled water. At growth stage 4 (stems not well developed), the whole plant of 'Rihane' barley was extracted. However, for the remaining growth stages roots, stems and leaves were extracted separately. Water extracts of 'Rihane' were bioassayed on 4 varieties of barley. Seedling growth bioassays revealed autotoxicity of barley which appeared to be more pronounced on radicle growth than coleoptile growth when plant parts were extracted near physiological maturity. Autotoxicity was not significant when 'Rihane' was simultaneously the donor and recipient of water extracts. When inhibitory activity of a water extract was observed, leaves were the most important source of allelopathic substances. Root extracts inhibited both radicle and coleoptile growth the least. Radicle and coleoptile showed contrasting responses to water extracts from roots, stems and leaves between stages 8 and 10. These results suggest that the allelopathic response by barley varies depending on source of allelochemicals (plant part) and the growth stage of the plant. Consequently, barley-barley cropping sequences should be avoided due to potential allelopathy of previous barley vegetative residues remaining in the field.