Effects of twist densities on allelopathic potential of Ipomoea cairica

To investigate the potential role of allelopathy in successful invasion of alien specie I. cairica, the effects of aqueous extracts from coronal roots, stems and leaves of I. cairica with twist densities of 1, 3, 9 and 18 plants per trellis were assessed on seed germination and seedling growth of Brassica parachinensis (target species). The different levels of allelopathic potentials in germination ratio and radicle lengths were associated with the twist density of I. cairica. Generally, at the same extract concentration and twist density, the inhibition ratio of extracts from coronal roots, stems and leaves of I. cairica on radicle lengths were greater than that on germination ratio, respectively. Inhibitory or stimulatory effects of coronal roots, stems and leaves of I. cairica were variable on radicle elongation and germination. At the same concentrations (except leaves at 0.02g/ml), the twist density of I. cairica exerted the allelopathic effects on radicle length more than on germination of receptor plant. The decreased alleopathic potentials at low twist density might show synergistic strategy of I. cairica, but increased potential at high twist density might increase the competitive strategy, to promote invasive capacity of I. cairica.