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Some Mosses Survive Cryopreservation without Prior Pretreatment

Abstract Pretreatment with sucrose or abscisic acid is thought to afford protection for plant tissues during dehydration and freezing by increasing desiccation tolerance. It is possible that the natural desiccation tolerance exhibited by some mosses will provide adequate protection during cryopreservation. The aim of this study was to determine whether three mosses with differing levels of desiccation tolerance would survive and regenerate after cryopreservation without prior encapsulation and pretreatment. The species chosen were Bryum rubens Mitt. (desiccation tolerant), Cyclodictyon laetevirens (Hook. & Tayl.) Mitt. (desiccation intolerant), and Ditrichum cornubicum Paton (limited desiccation tolerance). Encapsulated and non-encapsulated protonemal samples were air dried for 18 days. After desiccation, 100% of B. rubens and 40% of D. cornubicum survived in both non-encapsulated and encapsulated samples. After freezing, 90–100% of B. rubens, and 30–20% of D. cornubicum survived in non-encapsulated and encapsulated samples, respectively, while C. laetevirens did not survive either dehydration or freezing. Cryopreservation reduced the growth rate of D. cornubicum and B. rubens. The reduction in growth rate of B. rubens was temporary, with that of encapsulated protonemata eventually exceeding controls. It was concluded from this study that the natural desiccation tolerance of some mosses would be adequate to allow them to survive cryopreservation without prior pretreatment.