INFLUENCE OF ETHANOL AND ETHYLENE ON THE SEED-GERMINATION OF 3 NYMPHAEID WATER PLANTS

1. Under anaerobic conditions cold stratified seeds of Nymphaea alba a nd Nuphar lutea germinated readily and released ethanol (up to 6-7 mM ethanol g(-1) DW), whereas seeds of Nymphoides peltata did not germina te and hardly any ethanol was released (up to 1.5 mM ethanol g(-1) DW) . Ethylene release by seeds of Nymphaea, Nuphar and Nymphoides incubat ed under hypoxic conditions could not be detected. 2. Under aerobic co nditions all Nymphaea and Nuphar seeds germinated, but at a lower rate compared with anaerobic incubation. Ethanol release under aerobic con ditions was low (1.5-2 mM ethanol g(-1) DW). Under aerobic conditions the seeds of Nymphoides germinated promptly and ethanol release was lo w (0-0.5 mM ethanol g(-1) DW). 3. Germination of Nymphaea and Nuphar s eeds in an ethanol solution (350 mM) was generally stimulated compared with that in water, but no significant effect was recorded if seeds h ad not received a cold treatment or had been stratified for 8 weeks. G ermination of Nymphoides seeds was inhibited in the ethanol solution u nless they had received a cold treatment of 12 weeks. 4. Germination o f Nymphaea and Nuphar was stimulated by ethylene (5 mu g l(-1)) but ge rmination in moist air was lower than under normal submersed condition s. A stimulating effect of ethylene on the germination of Nymphoides s eeds was also evident. 5. It is suggested that ethanol and ethylene pl ay an important role in determining niches for germination, contributi ng to the zonation of these nymphaeids in a water body.