The high mountain pottioid moss Molendoa hornschuchiana (Hook) Lindb. ex Limpr. is a very rare and critically endangered bryophyte species in Europe in need for ex situ conservation. A 25-year-old herbarium sample was used to revive and propagate this species for further reintroduction and introduction to potential natural habitats. The reviving of “dead” herbarium specimen was achieved by disposing of axenical organisms as well as adjusting condition for developing secondary protonema, bud inductions, and optimization of gametophyte propagation in vitro condition.
The influence of exogenously added growth regulators on the morphogenesis of this species was studied. The plants were cultured in the two basic types of media, viz., BCD and half-strength Murashige and Skoog (MS) supplemented with different concentrations (0.01–0.3 μM) of indole-3-butyric acid (IBA) and N6-benzyladenine (BA) under a 16-h photoperiod. The influence of growth regulators on gametophores multiplication in vitro as well as on protonemal diameter was recorded. Well-developed gametophores were obtained on BCD medium, whereas on half-strength MS medium, secondary protonema was produced, both on hormone-free and supplemented substrate exclusively. Based on multiplication index in vitro, maximum development of gametophores was realized on BCD medium supplemented with 0.3 μM IBA and 0.1 μM BA. However, the widest diameter of secondary protonema was obtained on BCD medium enriched with low concentration of both BA (0.01 and 0.03 μM) and constant concentration of IBA (0.03 μM). Chemical names used: indole-3-butyric acid (IBA), N6-benzyladenine (BA), Murashige and Skoog medium (MS).