Unieke manier van vegetatieve voortplanting bij watervedermos (Fissidens fontanus)

Abstract

In a Bryonet discussion about Fissidens fontanus (Octodiceras) in May 2016, Jim Dickson asked whether anyone could throw light on Dixon’s (1924) statement that it is not unusual for the capsule to fall off and new plants to spring from the margins of the calyptra. A possible source for this statement could have been an illustration showing a shoot arising from the inner part of the calyptra of Octodiceras published by Britton in 1902. In the Bryonet discussion that followed, several participants suggested this might be a once-only observation. We decided to repeat and extend the culture experiments that van der Kamp conducted in 2009, in which plants of F. fontanus successfully produced sporophytes (van der Kamp 2018). For this study, we collected F. fontanus from a submerged population on the brick stone wall in a canal in the city of Utrecht (River Kromme Rijn) in February 2017. The plants we collected were very eroded and damaged by grazing invertebrates. To prevent the plants from being overgrown by other organisms, e.g. algae, the plants were transferred into clean bottles and new water fortnightly. The detritus, which in the earlier experiments was thrown away, was in the new experiment accurately inspected on the presence of detached sporophytes. Many sporophytes were found, not only in the detritus at the bottom of the tank, but also floating at the water surface close to the rim of the glass. During the months of April, May, and June, in total c. 175 released sporophytes have been collected, but after this period no new sporophytes were found. The detached sporophytes were placed into small bottles in order to follow their development. After a few months the majority of the calyptrae on these sporophytes developed juvenile plants. All juvenile plants originated at the calyptra base at the inner face. We have come to the conclusion that the production of juvenile plants from the calyptrae of F. fontanus is not just a once-only event but reflects a regular strategy for vegetative reproduction and dispersal.