Autotoxicity of Ambrosia artemisiifolia and Ambrosia trifida and its significance for the regulation of intraspecific populations density.

Ambrosia artemisiifolia and Ambrosia trifida are annual invasive plants that cause serious harm to agriculture, animal husbandry, and human health. Based on the important characteristic of high-density, cluster distribution of their populations, it is speculated that its autotoxins have an effect on density regulation. This study explored the regulation of autotoxicity on intraspecific density. We used water extracts from two plants to compare and verify the autotoxicity of seed germination, analysed the components of autotoxins. The results showed that A. artemisiifolia and A. trifida had significant autotoxicity, and the highest inhibition rates on seed germination were 27.21% and 77.94%, respectively; ultra-performance liquid chromatography tandem mass spectrometry analysis revealed that chlorogenic acid, caffeic acid, p-coumaric acid, and vanillin were the main autotoxins of the two plants. After the seeds were washed with water, the germination recovery rate of seeds increased with the increased of inhibition degree of autotoxins treatment. Therefore, this study verified the autotoxicity of A. artemisiifolia and A. trifida, which can promote and inhibit the seed germination of A. artemisiifolia and A. trifida to regulate intraspecific competition.