THE ROLE OF FLOODING RESISTANCE IN THE ESTABLISHMENT OF RUMEX SEEDLINGS IN RIVER FLOOD PLAINS

1. This study deals with resistance to complete submergence of seedlings of Rumex acetosa, R. crispus and R. palustris. 2. Seedlings of R. crispus and R. palustris appeared to be more resistant to flooding than those of R. acetosa under both field and greenhouse conditions. 3. Younger seedlings of all species were able to survive a longer flooding period than older ones. 4. When completely submerged the three Rumex species showed a low, but significant, photosynthetic activity. In R. crispus and R. palustris photosynthetically produced oxygen is released by the roots. Excised Rumex root tips have a low hypoxia tolerance, but that of R. acetosa was the lowest. This correlates with a high rate of ethanolic fermentation in both R. crispus and R. palustris and a low rate in R. acetosa. 5. The overall resistance to flooding of Rumex seedlings established from field, greenhouse and laboratory experiments showed a relationship with their site distribution in a flooding gradient of river Rhine.