Phytotoxic effects of Stellera chamaejasme L. root extract

Stellera chamaejasme is a traditional Chinese medicinal plant with a wide range of medicinal properties and biological activity. In order to evaluate the phytotoxity of S. chamaejasme, the effects of aqueous extracts (6.25, 12.5, 25, 50 and 100 g/L) prepared from roots was studied on the seed germination and seedling growth of rapeseed (Brassica napus), sesame (Sesamum indicum), wheat (Triticum aestivum) and maize (Zea mays). The treatments with high concentration extract (50 and 100 g/L) significantly reduced the germination rate of four crops compared with the control but the treatments with low concentration extract (from 6.25 to 25 g/L) had no obvious inhibitory effect. The mean germination time (MGT) of rapeseed and sesame increased with increasing extract concentration generally. The MGT of wheat and maize extended only at above 50 g/L concentration and at 100 g/L concentration respectively, whereas the treatments at 6.25, 25 and 50 g/L had a decreased effect on MGT of maize. The concentration-dependent effects were also found on shoot length, root length, number of lateral roots and dry weight of rapeseed, wheat and sesame seedling. Lower concentration extract treatments (6.25, 12.5 and 25 g/L) significantly promoted the seedling growth of maize, whereas the higher concentrations extracts had inhibitory effect. The results demonstrated that the high concentration aqueous extracts from S. chamaejasme had strong phytotoxity on seedlings growth of tested species. Dicotyledonous plants (rapeseed and sesame) were more sensitive to S. chamaejasme extract than monocotyledonous plants (wheat and maize). This result might be an important reference for further investigating the phytotoxic effect of S. chamaejasme for weed control.