Allelopathic effect of p -coumaric acid on American ginseng and its physiological mechanism

The cultivation of American ginseng (Panax quinquefoliurn L.; Araliaceae) is frequently hindered by problems during replanting. Our previous studies showed that p-coumaric acid significantly inhibited the radicle growth of American ginseng embryos grown on filter paper. The objectives of the study were to determine the allelopathic effects of p-coumaric acid on embryos of American ginseng grown in soil, to evaluate the effects of p-coumaric acid on adult plant growth, and to identify the physiological mechanism involved. The role p-coumaric acid played in the growth of American ginseng embryos was investigated using natural soil to mimic real conditions in the field. We also studied how p-coumaric acid affected the growth of 2-year-old American ginseng toots grown in nutrient solution. In conclusion, our data showed that p-coumaric acid exerts autotoxic effects on both embryos and seedlings of American ginseng and that these allelopathic effects might be partially achieved via the inhibition of photosynthesis in leaves of adult plants.