Rapid assessment of fern spore quality using microscale electrical conductivity testing

Ex situ spore banks are essential for fern conservation and research, yet traditional germination tests for assessing spore quality are time consuming and labor intensive. We explored whether electrical conductivity (EC), a rapid proxy for seed vigor, could offer an efficient alternative for evaluating fern spore quality.

Using chlorophyllous spores of Plenasium banksiifolium, we developed a microscale EC protocol (0.01-g spores, 1-h immersion) to track EC and germination over eight weeks of storage. Spore longevity (p ₅₀) was estimated via probit analysis, and correlations among EC, viability, and longevity were assessed.

Fresh spores from different individual plants showed varied initial EC (EC₀) values, with lower EC₀ values associated with longer longevity (p ₅₀). During storage, EC values increased over time, while germination percentage declined. The relative EC ratio (EC_i/EC₀) showed significant negative correlations with germination percentage, with a ratio of ~2 indicating 50% viability loss and ~3 signaling complete viability loss.

The EC test presents a promising approach for rapidly assessing spore viability and longevity. Lower initial EC (EC₀) values predicted greater initial spore viability and longer longevity, likely reflecting differences in spore maturity. The relative EC_i/EC₀ ratio effectively tracked viability loss, supporting its use in improving spore bank management.