biochemistry; tree rings; sugars; stable isotopes; tree physiology
Lehmann Marco M, Ghiasi Shiva, George Gavin M, Cormier Marc-André, Gessler Arthur, Saurer Matthias, Werner Roland A (2019), Influence of starch deficiency on photosynthetic and post-photosynthetic carbon isotope fractionations, in Journal of Experimental Botany
, 70(6), 1829-1841.
Gessler Arthur, Cailleret Maxime, Joseph Jobin, Schönbeck Leonie, Schaub Marcus, Lehmann Marco, Treydte Kerstin, Rigling Andreas, Timofeeva Galina, Saurer Matthias (2018), Drought induced tree mortality – a tree-ring isotope based conceptual model to assess mechanisms and predispositions, in New Phytologist
, 219(2), 485-490.
Lehmann Marco M., Goldsmith Gregory R., Schmid Lola, Gessler Arthur, Saurer Matthias, Siegwolf Rolf T.W. (2018), The effect of18
O-labelled water vapour on the oxygen isotope ratio of water and assimilates in plants at high humidity, in New Phytologist
, 217(1), 105-116.
Blees Jan, Saurer Matthias, Siegwolf Rolf T.W., Ulevicius Vidmantas, Prevôt André S.H., Dommen Josef, Lehmann Marco M. (2017), Oxygen isotope analysis of levoglucosan, a tracer of wood burning, in experimental and ambient aerosol samples, in Rapid Communications in Mass Spectrometry
, 31(24), 2101-2108.
Lehmann Marco M., Gamarra Bruno, Kahmen Ansgar, Siegwolf Rolf T.W., Saurer Matthias (2017), Oxygen isotope fractionations across individual leaf carbohydrates in grass and tree species δ 18 O of individual leaf carbohydrates, in Plant, Cell & Environment
, 40(8), 1658-1670.
Stable carbon and oxygen isotope ratios of plant materials are versatile tools in climatic and ecophysiological research. The combined use of the two isotope ratios has great potential because the fundamental processes of carbon uptake and water loss can be partly disentangled due to different isotope fractionations for carbon and oxygen during photosynthesis and transpiration. This method has been applied already in many studies, but has some limitations related to the use of bulk plant matter which consists of a complex mixture of different compounds with different history regarding time of production, chemical pathway and pool turnover time. Compound-specific isotope analysis therefore provides a more detailed view on the biochemical fractionation processes involved and should enable a better mechanistic understanding of the important steps of isotope fractionation during photosynthesis and downstream metabolism. So far, however, only techniques for compound-specific carbon isotope analysis have been available. Recently, we have now successfully developed a new method for GC-pyrolysis-isotope-ratio-MS of d18O based on methylation for a range of carbohydrates (including the most common sugars such as sucrose, fructose, glucose and sugar alcohols). This opens for the first time the possibility of compound-specific dual isotope analysis for the investigation of fractionation processes in plants. We will build upon these promising advances by conducting a dual-isotope labelling in the greenhouse and by studying natural carbon and oxygen isotope variations in the field, with a focus on the effect of drought. In the greenhouse experiment, we will expose tree saplings to a drought treatment, while another group of trees will be well watered, and then apply a puls-labelling. We will then follow the isotope signal in individual compounds by multiple sampling from the leaves, phloem and the stem. In the field studies, we will measure natural isotope variations during the growing season in mature forests. By analyzing the relationship between weather conditions and the isotope ratios in different plant parts, we will be able to detect the response of both isotope ratios in leaf sugars to the actual environmental conditions as well as the changes later on in other tissues related to post-photosynthetic fractionation and exchange processes.By extending the dual isotope method from the bulk level to the level of individual molecules, we will improve the quantification of isotope fractionation in plants and therefore contribute to a more reliable application of stable isotopes in various fields of the environmental sciences.