Beerling, David

Gilmour, Iain

Self, Stephen

Sephton, Mark

Sephton, Sarah

Watson, Jonathan

Wellman, Charles

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsSpore chemistry as a proxy for UV-B fluxConference or Workshop ItemHow to cite:Watson, Jonathan; Sephton, Mark; Sephton, Sarah; Beerling, David; Self, Stephen; Gilmour, Iain and Wellman,Charles (2005). Spore chemistry as a proxy for UV-B flux. In: 22nd International Meeting on Organic Geochemistry,12-16 Sep 2005, Seville, Spain.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://linkinghub.elsevier.com/retrieve/pii/S0146638006002397Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukSpore chemistry as a proxy for UV-B flux  Jonathan S. Watson1, Mark A. Sephton1,a, Sarah V. Sephton2, David J. Beerling3, Stephen Self2, Iain Gilmour1, Charles H. Wellman3  1Planetary and Space Sciences Research Institute, Open University, Milton Keynes, MK7 6AA, UK 2Department of Earth Sciences, Open University, Milton Keynes, Buckinghamshire, MK7 6AA, UK 3Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK aPresent address: Department of Earth Science and Engineering, Royal School of Mines, Imperial College, London, SW7 2BP, UK  Placing current increased terrestrial UV-B fluxes, due to the seasonal depletion of the stratospheric ozone layer, in a historical context is difficult due to a lack of long-term (century or more) instrumental records and necessitates developing proxy indicators. One promising line of enquiry derives from the response of plants to increased near-surface solar fluxes of harmful ultraviolet radiation in the 280 – 315 nm wavelength (UV-B) (Rozema et al. 2001, 2002). Plants exposed to increased UV-B radiation typically experience a number of detrimental effects, including damage to proteins, membrane lipids and DNA. To reduce this damage, many plants, animals and microbes accumulate UV-B protecting pigments (Cockell & Knowland 1999; Rozema et al. 2001, 2002). Here, we evaluate the potential of a promising candidate for such a proxy, which is based on changes in the chemical composition of spores in response to variations in near-surface UV-B fluxes, in a field setting. We obtained spores from five populations of the tropical lycopsid Lycopodium cernuum growing across an altitudinal gradient (650-1981 m a.s.l.) in S.E. Asia with the assumption that they experienced a range of UV-B radiation doses. Spores from each population were analyzed for UV-B protecting compounds using micro-Fourier transform infrared spectroscopy (micro-FTIR) and thermolchemolysis-GC-MS.   The data reveal the presence of various functional groups associated with UV-B protecting pigments including OH, C=O and C=C. Thermochemolysis and subsequent pyrolysis liberated UV-B pigments (ferulic and para-coumaric acid) from the spores. All of the aromatic compounds liberated from spores by thermochemolysis and pyrolysis were active in UV-B protection. We show systematic increases in micro-FTIR aromatic absorption (1520 cm-1) and olefinic or aromatic absorption (829 cm-1) with altitude that reflect a chemical response to higher UV-B flux. Our results indicate that detailed chemical analyses of historical spore samples could provide a proxy for stratospheric O3 layer variability and UV-B flux over historical (century to millennia) timescales.  Figure 1: Total ion chromatogram of products from a typical Lycopodium cernuum sample liberated at 300 ºC in the presence of TMAH  REFERENCES Cockell, C. S., Knowland, J., 1999. Ultraviolet radiation screening compounds. Biological Reviews. 74, 311-345. Rozema, J., Broekman, R.A., Blokker, P., Meijkamp, B.B., de Bakker, N., van de Staaij, J., van Beem, A., Ariese, F., Kars, S.M., 2001. UV-B absorbance and UV-B absorbing compounds (para-coumaric acid) in pollen and sporopollenin: the perspective to track historic UV-B levels. Journal of Photochemistry and Photobiology B 62, 108-117. Rozema, J., van Geel, B., Björn L.O., Lean, J., Madronich, S., 2002. Towards solving the UV puzzle. Science 296, 1621-1622.   P 

Spore chemistry as a proxy for UV-B flux

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Spore chemistry as a proxy for UV-B flux

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