Allocation of freshly assimilated carbon into primary and secondary metabolites after in situ C-13 pulse labelling of Norway spruce (Picea abies)

作者：Heinrich Steffen^*; Dippold Michaela A; Werner Christiane; Wiesenberg Guido L B; Kuzyakov Yakov; Glaser Bruno

来源：Tree Physiology, 2015, 35(11): 1176-1191.

DOI：10.1093/treephys/tpv083

• amino acid pathways
• carbohydrate turnover
• carbon allocation
• compound-specific isotope analysis
• lipid biosynthesis
• metabolite tracing
• photosynthetic partitioning

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 C-13 pulse labelling 15 days after bud break. The C-13 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 C-13) but also into stOC (33.9%). Needle growth, however, also caused high C-13 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 C-13 enrichment of their key amino acids. In addition, C-13 was strongly allocated into the n-alkyl lipid fraction (0.3% of recovered C-13), whereby C-13 allocation into cellular and cuticular exceeded that of epicuticular fatty acids. C-13 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 C-13 pulse labelling with compound-specific C-13 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 C-13 and kept most of the assimilated C in the growing needles.

• 出版日期2015-11