Allelopathic Interactions of Parthenium hysterophorous with Kidney Bean, Phaseolus vulgaris

Allelopathy, an important mechanism in invasive species stems from the lack of coevolved tolerance of indigenous species to novel chemicals released by the invader species. These chemicals are key to successful invasive of species of natural plant communities and ecosystems. This study analyzed the allelopathic effects of the invasive plant, Parthenium hysterophorous on the growth of kidney beans (Phaseolus vulgaris). One hundred and fifty viable kidney bean seeds were washed in distilled water, and transferred in triplicates to pots with wet sterile sand. Ten grams of freshly collected Parthenium leaves and roots were weighed, grounded separately using a mortar and a pestle, mixed with 100 ml of distilled water in a beaker and left for 24 hours in a dark at a room temperature (250C). The aqueous extract filtrates were used in experimental treatments. While untreated (control) seeds germinated on day 4 seeds treated with leaf extract germinated on day 14 and day 9 for the root extract. Leaf extract inhibited germination and sprouting of new leaves more effectively than root extract. Leaves in control seeds appeared on day 1 after germination. In treated seeds, leaves appeared on the 4th day then stagnated until day 15 when more leaves sprouted. Root extract significantly depressed seed germination. The number of new leaves increased significantly in control seedlings compared to the treated ones. Combined root and leaf extracts highly significantly inhibited of seed germination and the number of new leaves. Additionally, combined treatment with root and leaf extracts significantly inhibited shoot growth, and the increase in leaf length and width. A comparison of the effectiveness of the root and leaf extracts showed that leaf extract was more effective in inhibiting shoot growth and leaf width than the root extract.