Day Versus Night Exposure of Two Ecologically Contrasted Moss Species to Stratospheric Conditions: Stress Tolerance as a Key to Survival

Two species of moss, representative of the two categories of ecological strategies typical for bryophytes (i.e. stress tolerator and ruderal), were selected for the initial assessment of their capacity to withstand the conditions of the stratosphere. Samples of moss were attached to the balloons and elevated to the stratosphere during both diurnal and nocturnal periods. Observations of morphological changes, chloroplast condition, and chlorophyll autofluorescence post-introduction were conducted to assess survival abilities. The results demonstrated that Orthotrichum anomalum, a stress-tolerant moss, exhibited significantly higher resilience under both tested conditions compared to the ruderal Physcomitrella patens. Consequently, for further assessment of survival abilities of plants under space- or Mars-like conditions, desiccation tolerant stress-tolerant species are recommended.