Abstract

Wild sunflower (Tithonia diversifolia) is an invasive weed in both tropical and subtropical cultivated lands and propagates through seeds and plant cuttings. Invasive plants have distinctive functional traits that enable their invasiveness. The objective of this study was to determine the in vitro suppression of germination of crop seeds by extracts of T. diversifolia. Two experiments were carried out, one in the laboratory and the other in the greenhouse. The laboratory experiment was set up in a completely randomized design, while the greenhouse experiment was set up in a Randomized Complete Block Design. The blocking factor for the greenhouse experiment was the distance from the greenhouse door. Both experiments were replicated five times. T. diversifolia parts (leaves, stem, roots, and whole plant) were used in this experiment. The Genstat statistical package was used to analyze the data. Results showed that whole plant, leaf, stem, and roots extracts significantly (p<0.001) inhibited germination, radicle, plumule, stem girth extension, and chlorophyll content of maize, sunflower, soybeans, sorghum, rapoko grass, and cowpeas. This study confirmed that T. diversifolia parts suppressed germination, radicle, plumule, stem girth extension, and chlorophyll content of maize, sunflower, soybeans, rapoko grass, and cowpeas. Therefore, allelopathy contributes to the invasiveness of the weed.

Key words: Growth inhibition, invasive, traits, colonize.