Intraspecific and interspecific allelopathy of invasive plants Plantago virgica and Daucus carota.
At present, the species number and distribution range of invasive plants are gradually expanding, and the probability that multiple invasive plants invade the same habitat is increasing. In order to explore the intra- and inter-specific allelopathy of these invasive plants and the effect of allelopathy on their competitive ability, Plantago virgica and Daucus carota were chosen as examples of invasive plants. Using the biological method in laboratory, the effects of different concentrations(CK, 0.005, 0.01 and 0.05 g.mL-1) of water extracts from different organs(root, stem or rachis, and leaf) of the two plants on seed germination and seedling growth of self and the other were analyzed. The concentration of the extract had the greatest influence on the seed germination and seedling growth of the two invasive plants, and there were significant interactions among the concentration, organs and species. In general, each concentration of water extracts from different organs of the two plants showed inhibition on seed germination of the two plants. The medium and low concentrations of extracts promoted the seedling growth of the same species to an extent. High concentrations of extracts, especially extract from leaves of D.carota, significantly inhibited the seed germination and the seedling growth of the two plants. The allelopathic synthesis effect index indicated that the higher the concentration of the extract, the stronger inhibition effect. The allelopathic effect of the over-ground part was stronger than the underground part and D.carota showed the strongest interspecific allelopathy to P.virgica. Consequently, it is important that the invasive plants compete with each other for the intraspecific and interspecific allelopathy in the invaded area.