Do spores of Tortula inermis (Brid.) Mont. deharden to desiccation tolerance during germination?

The potential for spores of a moss to deharden to desiccation tolerance during the 48 hours prior to germination is investigated for perhaps the first time in a moss. Spores from capsules of Tortula inermis (Brid.) Mont. stored for 13 years desiccated in darkness were rehydrated for 3, 6, 12, 24, 36, or 48 hours and then rapidly dried to equilibration with c. 34% relative humidity at c. 22°C. The spores were then rehydrated and germination observed on days 3, 7, and 14. Control spores that were not subject to desiccation began to germinate on day 3, and reached 50% germination by day 7 postrehydration. Spores dried rapidly 3-24 hours postrehydration exhibited control levels of germination (50-60%) by day 14 postrehydration, indicating that spores did not deharden during the first 24 hours. However, the germination percentage of spores dried rapidly at 36 and 48 hours postrehydration declined to c. 20%, indicating a vulnerability to desiccation just prior to germination. During this latter period, the percentage of abortive spores is relatively high, and appeared to have aborted in a 12-hour period (24-36 h). Nevertheless, 20% of the spores survived a rapid drying event just prior to germination. This strategy of water stress tolerance ensures survival capabilities even during interruptions of the germination process by sudden, harsh, desiccation events where the hydrated spore desiccates in under an hour. Given known dehardening times of ≥7 days in bryophyte species studied, dehardening dynamics of spores is of the shortest duration known thus far in bryophytes (1.5 days).