The Effect of Extracts of Decomposing Shoots of Tithoniarotundifolia on the Germination and Seedling Growth of Vignaunguiculata, Glycine max, Zea mays and Sorghum bicolor
Otusanya, O.O; Ilori , O.J

Abstract
The phytotoxic effect of decomposing shoots of Tithoniarotundifoliaon Vignaunguiculata, Glycine max, Zea mays and Sorghum bicolor was investigated. The germination studies were carried out by raising seedlings in clean oven dried Petri dishes which had been lined with Whatman No 1 filter paper. The filter paper in each Petri dish allocated to the control was moistened with 10 ml of distilled water while 10 ml methanolic and water extracts of the decomposed shoots of T. rotundifolia were used for the treatments.The germination percentage, plumule length, radicle length, fresh and dry weights of plumule and radicle were determined according to standard methods. The data obtained were subjected to ANOVA. Treatment means were compared using least significant difference (LSD P < 0.05). The germination and growth of the juvenile seedlings of all the target test crops were significantly inhibited by themethanolic and water extracts. The phytotoxicity of themethanolic extracts was significantly higher than that of the water extracts showing that theallelochemicals in the decomposed tissues were better extracted in the methanol solvent than in water. Extracts of freshly decomposed shoot tissues were found to be more potent and significantly inhibited the germination and growth of the juvenile test crops at p < 0.05. In some cases, the germination and growth parameters of the test crops were stimulated with the increase in the period of decomposition of the shoot from which the extracts were prepared. It was concluded that the process of decomposition reduced or nullified the phytotoxicity of the extracts.

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