Abstract: Tissue culture methods were used to simulate the allelopathy effect of root exudates and plant aqueous extracts of continuously cropped soybean under sterilized conditions. The results show that the exudates and extracts both apparently affect the growth and physiological activities of second-batch seedlings, which may be related to the disturbance in the metabolism of plant hormones. The known allelochemicals as vanillic acid, vanillin and p-hydroxybenzoic acid were detected from both the exudate and the extract, and the continuous cropping obstacle of soybean may be related to their deleterious effect.

Key words: Soybean, Continuous cropping obstacle, Allelopathy