Allelopathy of Angelica sinensis at vegetative stage

To investigate the relationship between autotoxicity and continuous cropping obstacle and to find a reasonable crop rotation system for Angelica sinensis (a common traditional Chinese medicinal plant).Aqueous extracts from root, stem and leaf of A. sinensis at vegetative stage were analyzed for autotoxicity and allelopathic effect on Brassica campestris, Triticum aestivum, Avena sativa (which are often grown in regions where A. sinensis grown). The results indicate that A. sinensis exhibits significant autotoxicity (sensitivity index M₃ = -0.258 3). The effect from stem and leaf extracts is stronger than root extracts, which also increases with increasing concentration.T. aestivum and A. sativa show resistance to A. sinensis allelopathy, with respective comprehensive sensitivity indexes (M) of -0.075 5 and -0.144 7, while B. campestris is sensitive at M₃ = -0.307 9. Bioassay result of B. campestris is inconsistent with practical planting and this may be due to interactions between allelochemicals and soil microbes or allelochemical transformation which reduces allelopathy potential. Being different from autotoxicity, allelopathic effect of A. sinensis root on the three other tested plants is stronger than stem and leaf extracts, and is positively correlated with extract concentration. It then can be concluded that autotoxicity is an obstacle to continuous cropping of A. sinensis cultivation; T. aestivum and A. sativa may be an alternative rotation for overcoming this obstacle.