EFFECTS OF DROUGHT AND FLOODING ON THE REPRODUCTION OF AN AMPHIBIOUS PLANT, RANUNCULUS-PELTATUS

Aquatic seedlings of Ranunculus peltatus Schrank were subjected to thr ee levels of drought (dry, saturated and flooded) at two different phe nological stages, vegetative stage and at onset of flowering. Changes in growth form, timing of flowering, number of flowers and fruits and the number of seeds per fruit were monitored to test the effect of dro ught on reproduction. Plants that were transferred to a terrestrial, b ut water-saturated, environment at a vegetative stage rapidly changed from an aquatic, spreading; elongated growth form to a prostrate growt h form and produced only slightly fewer seeds per pot (86) than the fl ooded control plants (93). Total seed production was decreased by 1000 seeds per pot in both saturated treatments compared to the control tr eatment. There was no significant difference in total seed production between plants encountering drought at a vegetative or a flowering sta ge (2471 vs. 2348 seeds per pot). Plants subjected to air drying of th e soil (no water added) at both phenological stages changed growth for m, but flower, fruit and seed production was negligible. The fact that total seed production was still relatively high under water-saturated conditions at both phenological stages may explains partially why thi s species is successful in temporary mac-shes where drought often occu rs during its lifecycle. (C) 1997 Elsevier Science B.V.