Effect of storage temperature on green spore longevity for the ferns Equisetum ramosissimum and Osmunda regalis.

Green spores of ferns lose viability quickly, and need specialized treatment for long-term conservation in germplasm banks. Dry storage at different temperatures was studied in green spores of Osmunda regalis and Equisetum ramosissimum. Changes in germination percentage, time to 50 percent of maximum germination (T50) and tendency for normal growth of the gametophyte were assayed during 24 months of storage. Spores stored at 25 degree C died within 1 month. Spores stored at 4 degree C maintained high viability for about 3 months, and then aging was evident by a decrease of final germination percentage, an increase in T50, and abnormal development of the gametophyte. Germination of spores stored at -25 degree C was highly variable during the storage period. Spores cryopreserved at -80 degree C and -196 degree C maintained high viability, rapid germination and normal growth throughout the study period. Cryopreservation of green spores is a feasible method to preserve viability and ensure normal gametophyte development for several years.