title: Malate as a key carbon source of leaf dark-respired CO2 across different environmental conditions in potato plants.
abstract: Dissimilation of carbon sources during plant respiration in support of metabolic processes results in the continuous release of CO2. The carbon isotopic composition of leaf dark-respired CO2 (i.e. δ (13) C R ) shows daily enrichments up to 14.8‰ under different environmental conditions. However, the reasons for this (13)C enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in δ(13)C of putative leaf respiratory carbon sources (δ (13) C RS ) are not yet clear. Thus, we exposed potato plants (Solanum tuberosum) to different temperature and soil moisture treatments. We determined δ (13) C R with an in-tube incubation technique and δ (13) C RS with compound-specific isotope analysis during a daily cycle. The highest δ (13) C RS values were found in the organic acid malate under different environmental conditions, showing less negative values compared to δ (13) C R (up to 5.2‰) and compared to δ (13) C RS of soluble carbohydrates, citrate and starch (up to 8.8‰). Moreover, linear relationships between δ (13) C R and δ (13) C RS among different putative carbon sources were strongest for malate during daytime (r(2)=0.69, P≤0.001) and nighttime (r(2)=0.36, P≤0.001) under all environmental conditions. A multiple linear regression analysis revealed δ (13) C RS of malate as the most important carbon source influencing δ (13) C R . Thus, our results strongly indicate malate as a key carbon source of (13)C enriched dark-respired CO2 in potato plants, probably driven by an anapleurotic flux replenishing intermediates of the Krebs cycle.
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland Institute of Agricultural Sciences, ETH Zurich, Universitaetsstr. 2, CH-8092 Zurich, Switzerland marco.lehmann@alumni.ethz.ch.
authors.forename: Marco M
authors.initials: MM
authors.lastname: Lehmann
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
authors.forename: Katja T
authors.initials: KT
authors.lastname: Rinne
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitaetsstr. 2, CH-8092 Zurich, Switzerland.
authors.forename: Carola
authors.initials: C
authors.lastname: Blessing
authors.affiliation: Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
authors.forename: Rolf T W
authors.initials: RT
authors.lastname: Siegwolf
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitaetsstr. 2, CH-8092 Zurich, Switzerland.
authors.forename: Nina
authors.initials: N
authors.lastname: Buchmann
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich, Universitaetsstr. 2, CH-8092 Zurich, Switzerland.
authors.forename: Roland A
authors.initials: RA
authors.lastname: Werner
mesh_terms: D000143:Acids / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D009930:Organic Chemicals / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D011198:Solanum tuberosum / Q000378:metabolism*; D013213:Starch / Q000378:metabolism; D013696:Temperature
chemical_list: D000143:Acids; D002247:Carbon Isotopes; D009930:Organic Chemicals; D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D013213:Starch
keywords: Compound-specific isotope analysis (CSIA); drought; organic acids; plant respiration; stable carbon isotopes; sugars; temperature; tricarboxylic acid (TCA) cycle.