Print PageCeratodon purpureus is a cosmopolitan moss species that grows in extreme climates ranging from hot, dry and high ultraviolet (UV) Australian environments to icy coastal Antarctica. Antarctic C. purpureus moss occurs in red and green forms and is known to be very resilient to damaging ultraviolet-B (280-315 nm; UV-B) radiation especially whilst desiccated.
We aim to determine 1) whether there is a difference between the photoprotective chemical signature of red and green forms of Antarctic C. purpureus, 2) whether these compounds are reduced in low light, and 3) whether their concentrations change along radiocarbon dated moss shoots of Antarctic C. purpureus.
We compare Antarctic C. purpureus in addition to two other Antarctic moss species grown under naturally different UV environments. Samples were collected in the 2011 and 2012 Antarctic summer seasons. Photoprotective compounds were extracted from moss that was 1) naturally exposed (red form) and shaded (green form), 2) grown in low UV laboratory conditions, and 3) growing under different screening treatments either blocking, reducing or transmitting UV radiation. Methanol (intracellular) and alkali hydrolysis (cell wall) plant extracts were analysed using UV-visible spectrophotometry and analytical high pressure liquid chromatography to monitor any change in compound concentrations.
Results/Conclusions
Both red and green forms of Antarctic C. purpureus localise ultraviolet-B absorbing compounds (or sunscreens) within cells and cell walls. These compounds have high photoprotection value especially for plants surviving under diminished stratospheric ozone. The red, exposed moss shows lower levels of intracellular sunscreens but contains significantly higher levels within its cell wall - perhaps sunscreens within cell walls more effectively suppress harmful UV-B radiation.
Early results show that Antarctic C. purpureus mosses grown in low UV environments have reduced cell wall UV-B screening compounds. In addition, the three Antarctic species seemed to thrive under reduced radiation during the recent 2012 field experiments. These preliminary results suggest that the synthesis of sunscreens in C. purpureus is enhanced by UV radiation and localised within cell walls during new growth. This implies that these cell wall sunscreens have a long-term protective role in this species. This presence and location of sunscreens in C. purpureus will be compared with other co-occurring Antarctic moss species. How these compounds change along 30-80 year old moss shoots will also be investigated. Our work demonstrates the importance of investigating cell wall sunscreens in plants and suggests that they could be much more widespread than so far identified.
phone 202-833-8773