Carbon isotope composition is widely used to distinguish plants with major photosynthetic pathways. Most terrestrial plants are C3 plants with δ13C values ranging from ‐24 to ‐34 ‰, whereas many aquatic, desert, salt marsh plants as well as tropical grasses have the dicarboxylic acid (C4) pathway and higher δ13C values from ‐6 to ‐19 ‰ [1]. However within these groupings there is variation and other factors contribute to differences in δ13C signatures i.e. environmental conditions and water use efficiency [2], plant parts and organs [3] and tissue ageing and decomposition [4]. Furthermore there is also δ13C variation within specific plant compounds i.e. alkanes, lipids [5], cellulose and lignin [6]. Cistanche is a genus of plants with worldwide distribution with no photosystem that obtain nutrients and water from the host plants whose roots parasitize. All of its fixed carbon derives from the host plant. Bulk carbon isotope analysis has been used to detect hosts in obliged and facultative parasitic plants, however matching is not always as expected; in general it is known that δ13C in parasitic plants tissue is slightly but consistently enriched as compared with the host by between 1.0 and 1.5 ‰ [7]. This difference provides a good chance for false matchings, especially when trying to assert host plants growing close together and mixed under the same environmental conditions, that also favours the occurrence of extensive and complex root systems i.e. wetlands or marshes [8]. The parasitic association between species and the obliged parasitic plant Cistanche phelypaea (L.) is studied in the Odiel Marshes Biosphere Reserve, Huelva, (SW Spain). The use of conventional carbon IRMS analysis of bulk lyophilized tissue was found of limited value to tie parasite and host plant. Pyrolysis compound specific carbon isotope analysis (Py‐CSIA) of bulk lyophilized tissue was a very accurate technique in associating a particular parasite with its host. This study also unambiguously detected hosts of C. phelypaea and effectively demonstrating its ability to thrive on both C3 (Arthrocnemum macrostachyum (Moric.), Limoniastrum monopetalum (L.) Boiss. and Halimione portulacoides (L) Aellen) and C4 (Atriplex halimus L.) photosystem‐type plants. Up to know no parasitism could be confirmed between C. phelypaea and the C4 photosystem‐type species Spartina densiflora Brong. (C4) Salsola sp. (cf. brevifolia) although not discarded, research is still in progress.

[1] P. Deines, "The isotopic composition of reduced organic carbon." In: P. Fritz and J.Ch. Fontes (Eds.), Handbook of Environmental Isotope Geochemistry, Vol. 1. Elsevier, New York, 329–406 pp [2] G.D. Farquhar, Aust. J. Plant Physiol. 10 (1983) 205–226 [3] M. Werth, Y. Kuzyakov, Plant Soil 284 (2006) 319–333 [4] M. Zech, R. Zech, B. Glaser, Chem. Geol. 242 (2007) 307–318 [5] J.W. Collister, G. Rieley, B. Stern, G. Eglinton, B. Fry, Org. Geochem. 21 (1994) 619–627 [6] E.A. Hobbie, R.A. Werner. New Phytol. 161 (2004) 371–385 [7] L.A. Cernusak, G. Tcherkez, C. Keitel, W.K. Cornwell, L.S. Santiago, A. Knohl, M.M. Barbour, D.G. Williams, P.B. Reich, D.S. Ellsworth, T.E. Dawson, H.G. Griffiths, G.D. Farquhar, I.J. Wright. Funct. Plant Biol. 36 (2009) 199–213 [8] M.J. Vepraskas, C.B. Craft (Eds), Wetland Soils: Genesis, Hydrology, Landscapes, and Classification (2nd Ed.) (2016) CRC Press, Boca Raton, FL, USA. 506p.

Comunicación oral presenta en el la XVI Reunión Científica de la Sociedad Española de Cromatografía y Técnicas Afines (SECyTA2016) O‐ENV‐2

Eds: González-Pérez, José Antonio.-- Almendros Martín, Gonzalo.-- González-Vila, Francisco Javier.-- Rosa Arranz, José M. de la

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