Allelopathic effects ofCitrus aurantium L. : II. Isolation, characterization, and biological activities of phytotoxins.

In an earlier work, we found that the failure of herbaceous plants to grow under sour orange was mainly due to an allelopathic mechanism. Four nonvolatile inhibitors were isolated by paper chromatography. Color reactions of all the inhibitors indicated that they are phenolic in nature. On the other hand, five volatile inhibitors were detected by gas chromatography, four of which were terpenes. All inhibitors reduced seed germination and/or seedling growth ofAmaranthus retroflexus.