DIFFERENTIAL-EFFECTS OF THE MICROBIAL METABOLITE, ACETIC-ACID, ON SPROUTING OF AQUATIC PLANT PROPAGULES

Subterranean vegetative propagules are important life cycle stages for some species of rooted aquatic plants. Sediments contain numerous com pounds resulting from anaerobic degradation of organic matter, includi ng acetic acid. Tubers, turions, and winter buds of Hydrilla verticill ata (L.f.) Royle, Potamogeton gramineus L., and Potamogeton pectinatus L. were exposed to acetic acid concentrations from 0 to 696 mmol l(-1 ) for 1-8 days. Hydrilla verticillata propagules were more sensitive t o acetic acid exposure than those of either Potamogeton species. Monoe cious H. verticillata propagules did not sprout at acetic acid concent rations of 17 mmol l(-1) or over, even at the shortest exposure time. Potamogeton gramineus winter buds and P. pectinatus tubers were less i nhibited between 17 and 87 mmol l(-1) if the exposure time was short ( 2 days or less). Sediment type did not influence the differential resp onse to acetic acid, but the presence of sediments ameliorated the eff ects of acetic acid somewhat. More than two-thirds of P. pectinatus tu bers sprouted after a 24 h exposure to 696 mmol l(-1) at 4 degrees C, at higher temperatures sprouting was greatly reduced. Hydrilla ventici llata tubers did not sprout following exposure to 17 mmol l(-1) at any temperature (4, 13, 19, and 25 degrees C) examined.