Generative reproduction of long stalked pondweed (Potamogeton praelongus Wulfen) in the laboratory

• Potamogeton praelongus has a deep physiological dormancy: stored seeds germinate better.
• Scarification of water-impermeable seed coat is necessary for germination.
• Multiple dormancy breaking measures enhance germination more effectively.

Generative reproduction of Potamogeton praelongus in the laboratory is a possible way to preserve this critically endangered species in the Czech Republic (CR) as well as the whole of central Europe and to increase the low genetic diversity of its populations. Different methods of seed storage, breaking seed dormancy, cultivation temperature, seed age and interactions of these factors were examined to determine the suitable conditions for generative reproduction of P. praelongus in the laboratory. The most suitable storage method was keeping dried seeds in paper bags and submerging them in water for one month before the test. The best results of breaking seed dormancy were gained by near-natural methods – stratification, effect of microbial activity in water, scarification. Also methods using synthetic chemical substances and multiple dormancy breaking measures were successful. Seeds germinated better at 28 ± 1 °C than at 21 ± 3 °C. The best cultivation medium was river water. The strongest interaction was found between the storage method and treatment of seeds before cultivation.Seeds stored for about one year germinated better than fresh or shortly stored (6–9 months) ones. Optimal conditions for generative reproduction of P. praelongus in the laboratory were determined to be used for preservation of this species in CR.