N deposition affects allelopathic potential of Amaranthus retroflexus with different distribution regions.

This study aims to determine the allelopathic potential of Amaranthus retroflexus (Ar) with different climatic zones on seed germination and growth of A. tricolor (At) treated with a gradient N addition. Ar leaf extracts only displayed significantly allelopathic potential on the underground growth of Ar but not the aboveground growth of At. The allelopathic potential of Ar leaf extracts on root length of At were enhanced under N addition and there may be a N-concentration-dependent relationship. The effects of the extracts of Ar leaves that collected from Zhenjiang on seed germination and growth of At may be higher than that collected from Jinan especially on root length of At under medium N addition. This reason may be the contained higher concentration of secondary metabolites for the leaves of plants that growths in high latitudes compare with that growth in low latitudes. This phenomenon may also partly be attributed to the fact that Ar originated in America and/or south-eastern Asia which have higher similarity climate conditions as Zhenjiang rather than Jinan. The allelopathic potential of Ar on seed germination and growth of acceptor species may play an important role in its successful invasion especially in the distribution region with low latitudes.