title: Allocation of freshly assimilated carbon into primary and secondary metabolites after in situ ¹³C pulse labelling of Norway spruce (Picea abies).
abstract: Plants allocate carbon (C) to sink tissues depending on phenological, physiological or environmental factors. We still have little knowledge on C partitioning into various cellular compounds and metabolic pathways at various ecophysiological stages. We used compound-specific stable isotope analysis to investigate C partitioning of freshly assimilated C into tree compartments (needles, branches and stem) as well as into needle water-soluble organic C (WSOC), non-hydrolysable structural organic C (stOC) and individual chemical compound classes (amino acids, hemicellulose sugars, fatty acids and alkanes) of Norway spruce (Picea abies) following in situ (13)C pulse labelling 15 days after bud break. The (13)C allocation within the above-ground tree biomass demonstrated needles as a major C sink, accounting for 86% of the freshly assimilated C 6 h after labelling. In needles, the highest allocation occurred not only into the WSOC pool (44.1% of recovered needle (13)C) but also into stOC (33.9%). Needle growth, however, also caused high (13)C allocation into pathways not involved in the formation of structural compounds: (i) pathways in secondary metabolism, (ii) C-1 metabolism and (iii) amino acid synthesis from photorespiration. These pathways could be identified by a high (13)C enrichment of their key amino acids. In addition, (13)C was strongly allocated into the n-alkyl lipid fraction (0.3% of recovered (13)C), whereby (13)C allocation into cellular and cuticular exceeded that of epicuticular fatty acids. (13)C allocation decreased along the lipid transformation and translocation pathways: the allocation was highest for precursor fatty acids, lower for elongated fatty acids and lowest for the decarbonylated n-alkanes. The combination of (13)C pulse labelling with compound-specific (13)C analysis of key metabolites enabled tracing relevant C allocation pathways under field conditions. Besides the primary metabolism synthesizing structural cell compounds, a complex network of pathways consumed the assimilated (13)C and kept most of the assimilated C in the growing needles.
authors.affiliation: Department of Agro-Ecosystem Research, BAYCEER, University of Bayreuth, Universitätsstraße 30, 95448 Bayreuth, Germany Soil Biogeochemistry, Martin-Luther University Halle-Wittenberg, von-Seckendorff-Platz 3, 06120 Halle, Germany steffen.heinrich@uni-bayreuth.de.
authors.forename: Steffen
authors.initials: S
authors.lastname: Heinrich
authors.affiliation: Department of Agricultural Soil Science, University of Göttingen, 37077 Göttingen, Germany.
authors.forename: Michaela A
authors.initials: MA
authors.lastname: Dippold
authors.affiliation: Department of Agro-Ecosystem Research, BAYCEER, University of Bayreuth, Universitätsstraße 30, 95448 Bayreuth, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Werner
authors.affiliation: Department of Geography, University of Zurich, CH-8057 Zurich, Switzerland.
authors.forename: Guido L B
authors.initials: GL
authors.lastname: Wiesenberg
authors.affiliation: Department of Agricultural Soil Science, University of Göttingen, 37077 Göttingen, Germany.
authors.forename: Yakov
authors.initials: Y
authors.lastname: Kuzyakov
authors.affiliation: Soil Biogeochemistry, Martin-Luther University Halle-Wittenberg, von-Seckendorff-Platz 3, 06120 Halle, Germany.
authors.forename: Bruno
authors.initials: B
authors.lastname: Glaser
mesh_terms: D002244:Carbon / Q000737:chemistry / Q000378:metabolism*; D002247:Carbon Isotopes; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D010368:Pectins / Q000737:chemistry / Q000378:metabolism; D028222:Picea / Q000737:chemistry / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D005227:Fatty Acids; D011134:Polysaccharides; D002244:Carbon; C007916:hemicellulose; D010368:Pectins
keywords: amino acid pathways; carbohydrate turnover; carbon allocation; compound-specific isotope analysis; lipid biosynthesis; metabolite tracing; photosynthetic partitioning