Effect of storage method on spore viability in five globally threatened fern species.

Spore germination of five globally threatened fern species [Culcita macrocarpa C. Presl, Dryopteris aemula (Aiton) O. Kuntze, D. corleyi Fraser-Jenkins, D. guanchica Gibby and Jermy and Woodwardia radicans (L.) Sm.] was determined after 1, 6 or 12 months of storage in glass vials (dry storage) or on agar (wet storage) at -20, 5 or 20 degrees C. In all species, storage technique, storage temperature and the technique-temperature interaction all had a significant effect on germination percentage. In most cases, the germination percentage was best maintained by wet storage at 5 or 20 degrees C. In the case of the hygrophilous species C. macrocarpa and W. radicans, 6 or 12 months' dry storage killed most spores. Only Woodwardia radicans germinated in the dark during wet storage at 20 degrees C. Wet storage at 5 degrees C prevented dark germination, and reduced bacterial and fungal contamination. Wet storage at -20 degrees C killed all or most spores in all species. In the three Dryopteris species, the differences among the storage conditions tested were smaller than in C. macrocarpa and W. radicans, and the decline in spore viability during storage was less marked, with high germination percentages being observed after 12 months of dry storage at all three temperatures. Dry storage, which has lower preparation time and space requirements than wet storage, was generally more effective at the lower temperatures (-20 or 5 degrees C).