Allelopathic effects of mesquite (Prosopis juliflora) foliage on seed germination and seedling growth of bermudagrass (Cynodon dactylon)

Allelopathic effects of aqueous extracts of 10, 20, 30, 40, 50 and 60 g dry mesquite (Prosopis juliflora) leaves in a litre of distilled water on seed germination and early growth of bermudagrass (Cynodon dactylon 'Common Bermuda') at 30 degrees C were investigated. The final germination percentage and the germination rate, as judged by corrected germination rate index (CGRI) and to a lesser extent by the time to 50% of the final germination (GT(50)), were significantly reduced by the extracts in comparison with the distilled water control. This reduction increased with increasing extract concentration, until germination was totally inhibited with the most concentrated extract. Both radicle and plumule lengths were also significantly retarded. The radicles, which did not elongate at all in the most concentrated extract, were more affected. Polyethylene glycol 2000 solutions, with the same pH and osmotic potentials as the extracts, resulted in a significantly higher germination percentage, CGRI and radicle growth rate than their corresponding extracts. A similar trend was exhibited by the plumules at the three highest concentrations only. These results indicate that the mesquite foliage contains water-soluble allelochemicals which could inhibit seed germination and significantly retard the rate of germination and seedling growth of bermudagrass. (C) 1998 Academic Press Limited.