GERMINATION OF MACROPHYTES FROM A DELAWARE-RIVER TIDAL FRESH-WATER WETLAND

The effects of burial and soil moisture (seeds were on the surface, or buried at 1 and 5 cm with drained, saturated, or hooded water levels) , inundation (Petri dishes, and open and closed jars), and storage (si milar to 0 and similar to 100% RH), as well as of light and various te mperature regimes, were examined. Focus was on ten species (Amaranthus cannabinus (L.) Sauer, Ambrosia trifida L., Bidens laevis (L.) BSP. I mpatiens capensis Meerb., Peltandra virginica (L.) Schott. & Endl., Ph alaris arundinacea L., Pilea pumila (L.) A. Gray, Polygonum arifolium L., Polyontum punctatum Elliott, and Sagittaria latifolia Willd.); fiv e others were also considered to a limited extent (Alisma subcordatum Raf., Carex lurida Wahlenb., Cicuta maculata L., Cuscuta gronovii Will d., and Pontederia cordata L.). Species varied in their germination re sponses. Those with the same seed bank strategy (transient or persiste nt) had different dormancy mechanisms although seeds with persistent s eed bunks required temperatures >5 degrees C and germination fur most was enhanced by light. Responses to burial and moisture level showed t hat larger seeded species were able to germinate from greater depth. b ut germination was greater in drained samples. There were three types of responses to inundation: (1) requirement for at least modest amount s of oxygen, (2) requirement for hypoxic conditions, and (3) those hav ing good germination regardless of inundation regime. Seed bank losses and relatively short seed bank longevity could be accounted for by ge rmination following afterripening, adverse effects of prolonged inunda tion. failed germination (e.g., germination at depths that preclude th e seedling from reaching the surface), and predation. Differences betw een the seed characteristics of species of this and those of other wet lands relate to the transient nature of the seed bank, and to wetland hydrology. Variable responses to drying have implications for wetland restoration projects.