Desiccated Syntrichia ruralis shoots regenerate after 20 years in the herbarium

The longest record for a moss withstanding continuous desiccation is 19 years. This report demonstrates that a herbarium specimen of Syntrichia ruralis (Hedw.) F. Weber & D. Mohr from southern Nevada, USA, has retained its viability for 20 years and 3 months. Fifty-eight shoots of a herbarium specimen collected in 1995 were cleaned and placed into culture using locally collected and sterilized sand. These shoots were kept hydrated and examined daily for 28 days for signs of regeneration. Five sets of three additional shoots from the herbarium specimen were assessed for chlorophyll fluorescence at intervals from 30 min to 8 days post-rehydration. About two-thirds of the shoots were viable: producing regenerative protonemata or shoots directly from the original shoots or leaves, with shoot apices not resuming growth despite most regeneration occurring towards the apex of shoots. Chlorophyll fluorescence measurements were similar to those of dead or severely compromised plant tissues over the first 48 h post-rehydration, with F-v/F-m levels <0.05. However, F-v/F-m levels rose to similar to 0.35 after 8 days as F-m values dropped, indicative of some viable tissues.