INFLUENCE OF EXTRACTS FROM FRESH SAMPLE OF FIVE TROPICAL WEEDS ON SEED GERMINATION AND EARLY SEEDLING DEVELOPMENT OF SELECTED CROP SPECIES

Abstract

The inhibitory potentials of extracts from five of the major troublesome weeds in arable crop production in the humid tropics were investigated. Extracts from fresh shoot of wild poinsettia (Euphorbia heterophylla L.)  Siam weed (Chromolaena odorate (L) R. M. King and Robinson) and

Itchgrass (Brottboellia cochinchinensis (Lour) Clayton) generally produced greater inhibitory effects on the early seed germination of tomato (Lycopersicon esculaentum Mill), pepper (Capsicum frutescens L.), and cowpea (Vigna unguiculata (L.) Walp) than their root extracts. Root extracts of nutsedge (Syperustuberrosus Rottb.) And speargrass (Imperata cylindrical (L.) Beauv) produced greater inhibitory effects on the development of the test crops than their shoot extracts. Both the root and shoot extracts from the various weed species produced no inhibitory effects on the germination of maize seeds. Siam weed and wild poinsettia shoot extracts delayed seed germination in millet (Penniselum maiwaStapf) and rice (oryza sativa L.Var. ITA  22) and inhibited their seedling developments.

The effects of extracts from the different weed species on the test crps on order of potency were siam weed > wild poinsettia > itchgrass > speargrass.

Although the early germination stages of all the test crops except maize, were generally delayed by the weed extracts, their final germination  was not significantly affected. The inhibitory effects tended to be more on the germination of smaller seeds (tomato, pepper, millet, and rice) than on bigger seeds (maize and cowpea) and the  development of young seedling root was more inhibited than that of young seedling shoot.