Embryos of the moss Aloina ambigua are inducibly desiccation tolerant (DT), requiring a slow-dry period to confer tolerance to air-dryness. Hardening to DT describes a condition of temporary tolerance to a rapid-dry event (<30 min from full turgor to air-dryness) that is conferred by a prior slow-dry event.
Brinda et al. found for the first time that moss embryos can indeed be hardened to DT, by first slowly drying embryos and equilibrating them at 50 % relative humidity, then rehydrating the embryos and exposing them to a rapid dry event at intervals of 24 h. The degree of hardening to DT is dependent upon the prior rate of slow-drying. Finally, a new metric for assessing DT is presented as the minimum rate of drying in order for shoots or embryos to recover undamaged upon rehydration.