Rapid loss of germinability and gradual loss of physiological activity in Japanese Dryopteris uniformis (Dryopteridaceae) spores stored in herbaria

Herbaria of museums and universities contain vast arrays of plant specimens. If seeds and spores from these specimens can be successfully germinated, they can help restore genetic diversity in current plant populations and even reestablish lost species. The spores of Dryopteris uniformis Makino (Dryopteridaceae) were collected from 23 specimens stored in the Herbarium of Osaka Museum of Natural History and the Niigata University Herbarium, and their germinabilities and physiological activities were examined using germination and tetrazolium staining tests, respectively. Although no germination was observed, some stained fern spores were confirmed from five specimens that had been stored for 0.3, 3.3, 4.9, 12.3, and 24.3 years, respectively. The number of partially stained spores rapidly declined over time; however, some spores were observed in specimens stored for >88 years (0.8% ± 0.3%). In germination tests using gibberellin, three spores germinated from specimens stored for 5.3 years. The discrepancy between spore germination and staining rates indicates that the loss of mitochondrial activity, which indicates spore death, occurs much later than that of germinability. This study will enhance our understanding of the potential viability of specimens preserved in herbaria.