Effect of Water Extract from Mexican Sunflower [Tithonia diversifolia (Hemsl.) A. Gray] on Germination and Growth of Tested Plants

The inhibitory activity of water extract from leaves, stems and roots of Mexican sunflower [Tithonia divers ifolia (Hemsl.) A. Gray] on seed germination and seedling growth of selected plants were examined in the laboratory. The water extract from mature leaves at the concentration of 10mg (dry weight)/ml showed slight effect on seed germination but caused significant reduction in seedling growth of most plants tested. The degree of inhibition on plant growth varied depending on plant species. The inhibitory activity of water extract from leaves and stems on growth of sorghum seedlings were similar but higher than the activity of water extract from roots. There was no difference in phytotoxic activity between the extract from green and senescent leaves. The water extract applied in soil also inhibited root growth of the plants tested but this inhibitory activity declined in the soil.