Effect of maturity level and desiccation process on liquid nitrogen storage of green spores of Osmunda japonica

Abstract

To improve storage of green spores by liquid nitrogen (LN), we studied the influence of spore maturity and desiccation process on storage of Osmunda japonica spores. Germination percentages of mature spores after drying for 12 h or equilibrating at 10–55 % relative humidity did not significantly differ from those of fresh spores. So we established that the critical water contents of mature spores were about 6.6 and 4.8 % by silica gel and equilibrating with saturated salt solutions, respectively. Germination percentages of post-mature spores after desication were lower than those of fresh spores. The viability of mature spores was always higher than the viability of post-mature spores following varying periods of storage in LN. The germination percentages of mature spores stored in LN after silica gel desication were comparable to those of mature spores desiccated with saturated salt solution, while desiccation with silica gel led to a marked decrease in germination percentages of post-mature spores during subsequent storage. In general, the level of maturity and desiccation process can have an impact on storage of green spores by LN storage. Mature spores can tolerate desiccation and freezing independent of the desication process. However, slow removal of intracellular water led to less damage and provided more protection to post-mature spores during storage. In addition, reduction in water contents of spores to approx. their critical levels can achieve the best results for long-term storage of spores.