Allelopathic activity ofLitchi chinensisSonn.

The present research was carried out to investigate the allelopathic activity of Litchi chinensis Sonn., an important exotic fruit plant of subtropical to tropical areas. The aqueous methanol extract of L. chinensis leaves at four different concentrations was examined against the germination of lettuce (Lactuca sativa L.) and barnyard grass (Echinochloa crus-galli L. Beauv.), and the seedling growth of cress (Lepidum sativum L.), lettuce, alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), Italian ryegrass (Lolium multiflorum Lam.) and barnyard grass. The hypocotyl/coleoptile and root growth of all test plants were significantly inhibited by the extracts at concentrations ≥0.01 g dry weight equivalent (dry wt. eq.) extract mL−1. The inhibitory activities of the extracts were proportional to the extract concentrations. At concentration 0.1 g dry wt. eq. extract mL−1, the extracts completely inhibited the hypocotyls of cress, lettuce and alfalfa, and the root growth of all test plant species. At the same concentration, a complete inhibition of lettuce seed germination and a significant delay of germination on barnyard grass were also observed. The I 50 values for the hypocotyl/coleoptile and root growth of test plants range from 0.002 to 0.079 g dry wt. eq. extract mL−1. These results suggest that L. chinensis leaf extracts possess allelopathic properties and contain allelopathic substances. Therefore, the plant could be used as a candidate for isolation and identification of those active substances, which may explore the interactions of L. chinensis with other neighbouring plants under natural settings. Further, the leaf extracts and/or their residue could be directly used as bioherbicides, or the active substances isolated from this plant may possibly be used as herbicide or templates for new natural, biodegradable herbicide for alternatives of cruel synthetic herbicides in most sustainable manner. To the best of our knowledge this is the first report about the allelopathic activity of L. chinensis.