Germination responses in Callitriche truncata Gussone

Abstract

This study investigated the germination responses of seeds of Callitriche truncata, an obligate hydrophyte that colonises temporary ponds in the Mediterranean, when subjected to different depths of burial and to varying patterns of initial flooding, and to examine the effect of flooding date on the growth and reproduction effort of this plant. All investigations were carried out at two different seed densities in order to investigate whether this factor would exert any effect on germination success and on accumulation of biomass. Seeds germinated from the 'no burial' treatment and from burial under 1cm} of sterile sediment with the rates of germination success declining rapidly with depth of burial. No germination was recorded from seeds buried deeper than 1cm. The density of seeds per pot did not influence the results significantly. There was no significant difference in germination success of seeds subjected to 'Autumn flooding' and 'Winter flooding' treatments or across seed densities. Plants grown during the 'Winter flooding' treatment produced less total biomass and a lower proportion of reproductive biomass at the end of the experiment than seeds grown during the 'Autumn flooding' treatment. Although characterised by lower reproductive success, later flooding still permitted completion of life cycles and restocking of the seed bank. These findings are generally consistent with the results of previous studies in other temporary waters of the Mediterranean.