Autotoxic potential of foliage on seed germination and early growth of mesquite (Prosopis juliflora)

Aqueous extracts of 10, 20, 40 and 60 g dry leaves of mesquite (Prosopis juliflora), in a line of distilled water, were tested for their autotoxic effects on seed germination and early seedling growth. With the exception of the effect of the least concentrated extract on the final seed germination, all extracts reduced seed germination percentage, and radicle and hypocotyl lengths considerably, in comparison with the distilled water control. This reduction increased with the increase of extract concentration throughout the germination period. The radicles, which did not elongate at all in the highest concentrated extract, were more affected than the hypocotyls. Using ground leaves mixed with sand in the ratios of 1:15, 1:10 and 1:5, (leaves: sand, by volume) compared to sand as a control, resulted in similar findings. The pH and the osmotic potentials of the extracts were not low enough to bring about such effects, so it could be concluded that the mesquite foliage contains water-soluble allelochemicals which could inhibit seed germination and seedling growth of the same species. (C)1995 Academic Press Limited