Assistant Professor University of Minnesota Saint Paul, Minnesota, United States
Abstract: Bryophytes are renowned for their ability to tolerate extended periods of desiccation, and some studies have found that exposing desiccated bryophytes to humid air prior to rehydration with liquid water aids in recovery. While little is known about this phenomenon in bryophytes, we know that numerous lichen photobionts can activate photosynthesis in the presence of water vapor alone. The ability to access water in the form of vapor can prove advantageous in both humid and dry environments as it broadens the conditions under which photosynthesis can occur.
In this study, we aimed to assess the extent of vapor-induced photosynthesis activation in morphologically diverse bryophytes from the Black Hills, SD, Grand Staircase-Escalante National Monument, UT, Hill Annex Mine State Park, MN, and Puerto Rico. We hypothesized that bryophytes from high-humidity habitats and bryophytes with lower shoot mass per area would display more effective use of water vapor in photosynthesis. We used an infrared gas analyzer and a chlorophyll fluorometer to measure CO2 uptake and Fv/Fm in these bryophytes under both vapor and liquid hydrating circumstances.
We found that numerous bryophytes activate photosynthesis through exposure to high-humidity air. CO2 uptake and Fv/Fm were almost always lower when hydrated with vapor than with liquid water. However, some taxa displayed nearly identical CO2 uptake rates in vapor and liquid. Bryophytes from Puerto Rico, the most humid location, displayed the lowest levels of vapor-induced CO2 uptake. Additionally, we found a positive correlation between shoot mass per area and area-scaled carbon uptake, with vapor holding capacity linking these variables together.
The results of this study help elucidate an exceptionally understudied phenomenon in bryophyte physiology. Furthermore, our broad examination of vapor hydration in bryophytes will prove useful in projecting outcomes for these organisms in the face of climate change. The ability of many bryophytes to use humid air as a water source suggests that it needs to be included explicitly in climatic niche models if present and future ranges are to be accurately predicted.
