Abstract

The allelopathic effects of fresh shoot aqueous extract of Tithonia diversifolia(Hemsl.) A. Gray was investigated on the germination of seeds and growth of young seedlings of Zea mays L. Although the fresh shoot aqueous extract did not show significant allelopathic effect on the germination of Z. mays, however, the radicle and plumule lengths of the seedlings were significantly inhibited by the fresh shoot aqueous extract. Also, the fresh shoot aqueous extract of T. diversifolia was found to significantly stimulate the growth of older plants of two weeks old and above. The application of fresh shoot aqueous extract of T. diversifolia was observed to significantly enhance the following growth parameters: fresh weight, dry weight, leaf area and ratio. In addition, chlorophyll a, chlorophyll b and total chlorophyll accumulation were reduced in these young plants. The study was able to reveal that fresh shoot aqueous extract of T. diversifolia could have differing effects (inhibitory and stimulatory), on seedling growth of this test crop, depending on plants growth stage.

Key words: Allelochemicals, allelopathy, fresh shoot aqueous extract, inhibitory, stimulatory, Tithonia diversifolia, Zea mays.