Award Date


Degree Type


Degree Name

Master of Science (MS)


Life Sciences

First Committee Member

Lloyd R. Stark

Second Committee Member

Elizabeth Stacy

Third Committee Member

Matthew Petrie

Fourth Committee Member

Clemens Heske

Number of Pages



Many terrestrial mosses of xeric environments experience excess light during extended periods of desiccation. While dry or hydrated, excess light energy can lead to formation of reactive oxygen species and photoinhibition (e.g. damage to Photosystem II) which affects photosynthetic stress and efficiency. This study aimed to determine the effect of duration dry and light intensity (PAR) on cultured shoots of the chaparral moss Timmiella crassinervis, as well as to elucidate the optimal rehydration light conditions for this species. I hypothesized that 1) mosses exposed to higher light intensities during desiccation would incur more damage upon rehydration than those exposed to lower light intensities, 2) lower light intensities during rehydration would be more conducive to recovery than higher light intensities, and 3) the combination of high light during desiccation and rehydration will be the most stressful. To this end, shoots were removed from culture, slowly dried for 55 h, moved to a growth chamber at 160 PAR, ~25 PAR, and darkness for 10 days, and rehydrated at their respective light level for 72 h. Chlorophyll fluorescence measurements were taken at 0, 24, 48, and 72 h to assess relative shoot health and recovery from desiccation and light stress. Desiccation- and recovery-light intensities showed a significant interaction effect on the recovery of photosynthetic stress (Fv/Fm) and operating efficiency (?PSII). However, desiccation-light level was more important for the recovery of Fv/Fm than recovery-light level. As hypothesized, high-desiccation light was most stressful regardless of the recovery-light level. Recovery of Fv/Fm was not affected by recovery light, but recovery of ?PSII was best under low light. Finally, light conditions during desiccation and rehydration may be conferring light acclimation to this species, highlighting the importance of light during these stages for not only recovery, but also photoprotection, which should be taken into consideration in the design and focus of future experiments.


Desiccation tolerance; Light acclimation; Light stress


Environmental Sciences | Plant Sciences | Terrestrial and Aquatic Ecology

File Format


File Size

4800 KB

Degree Grantor

University of Nevada, Las Vegas




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