Abstract

American ginseng (Panax quinquefolium L.) cannot be replanted in the same soil consecutively. Inhibitory allelopathy has been reported to be one of the factors in its replant failure. Ginsenosides is the important allelochemicals of ginseng. However, the allelopathic effects of ginsenosides on American ginseng are not well known. This paper investigated the effects of ginsenosides on American ginseng seedling growth, the activity of antioxidant enzymes and the content of malondialdehyde (MDA) in seedling radicles. Results showed that total ginsenosides, panaxadiol ginsenosides and ginsenosides-Rb group have inhibitory effects at higher concentrations but at low concentrations they have stimulatory effects on the growth of American ginseng seedling. The panaxatriol ginsenosides have stimulatory effects on the growth at various concentrations. All the ginsenosides treatments caused an increased MDA content. Under total ginsenosides treatment, catalase (CAT) activity was not detected. Both superoxide dismutase (SOD) and peroxidase (POD) activities increased at low concentrations, and they decreased at high concentrations, under panaxadiol ginsenosides treatment, CAT activity was not detected. Both SOD and POD activities decreased, under panaxatriol ginsenosides treatment, CAT activity was not detected. SOD activities significantly increased while POD activities significantly decreased, under ginsenosides-Rb group treatment, the SOD, CAT and POD activities increased at low concentrations while decreased at high concentrations. The phytotoxicity of ginsenosides is one of many possible factors contributing to ginseng replant failure.

Key words: American ginseng (Panax quinquefolium L.), allelopathy, ginsenosides, replant failure.