Plants in dryland ecosystems experience extreme daily and seasonal fluctuations in light, temperature, and water availability. We used an in-situ field experiment to uncover the effects of natural and reduced levels of UV on maximum PSII quantum efficiency (Fv/Fm), relative abundance of photosynthetic pigments and antioxidants, and the transcriptome in the desiccation-tolerant desert moss Syntrichia caninervis. We tested the hypotheses that: (1) S. caninervis plants undergo sustained thermal quenching of light (non-photochemical quenching; NPQ) while desiccated and after rehydration, (2) a reduction of UV will result in improved recovery of Fv/Fm, but (3) one year of UV removal will de-harden plants and increase vulnerability UV damage to photosynthetic efficiency. All field-collected plants had extremely low Fv/Fm after initial rehydration but recovered over eight days in lab-simulated winter conditions. UV-filtered plants had lower Fv/Fm during recovery, higher concentrations of photoprotective pigments and antioxidants such as zeaxanthin and tocopherols, and lower concentrations neoxanthin and chlorophyll b than plants exposed to near natural UV levels. Field-grown S. caninervis underwent sustained NPQ that took days to relax and for efficient photosynthesis to resume. Reduction of solar UV radiation adversely affected recovery of Fv/Fm following rehydration.
Desert mosses withstand intense sunlight while desiccated and metabolically inactive. We used in situ field experiments to uncover the effects of natural and reduced levels of UV radiation on maximum Photosystem II (PSII) quantum efficiency (Fv/Fm) and on the relative abundance of photosynthetic pigments and antioxidants in Syntrichia caninervis. We tested the hypothesis that if UV is a stressor, reduction of natural UV levels will result in increased photosynthetic efficiency, but that such reduction will de-harden plants and increase vulnerability to PSII damage with UV exposure. We also measured photosynthetic efficiency over a simulated winter recovery period to assess sustained non-photochemical quenching (NPQ) and its subsequent relaxation. Finally, we measured the effect of UV reduction on photosynthetic pigment and antioxidant abundance. All fieldcollected plants had low Fv/Fm at collection but recovered over eight days in winter conditions. Plants in the low-UV treatment had lower Fv/Fm during recovery than those exposed to natural UV levels and had higher zeaxanthin, lutein, tocopherols, and a higher ratio of chlorophyll a to chlorophyll b. Natural S. caninervis undergoes sustained NPQ that takes days to relax and for efficient photosynthesis to resume. Reduction of UV radiation from sunlight has adverse effects on recovery of Fv/Fm.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.