Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 66, Issue 19, Pages 5769-5781Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/erv279
Keywords
Compound-specific isotope analysis (CSIA); drought; organic acids; plant respiration; stable carbon isotopes; sugars; temperature; tricarboxylic acid (TCA) cycle
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Funding
- SNF [205321_132768]
- SNF via R'equip [206021_128761]
- Swiss National Science Foundation (SNF) [205321_132768] Funding Source: Swiss National Science Foundation (SNF)
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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. delta C-13(R)) shows daily enrichments up to 14.8% under different environmental conditions. However, the reasons for this C-13 enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in delta C-13(R) of putative leaf respiratory carbon sources (d13CRS) are not yet clear. Thus, we exposed potato plants (Solanum tuberosum) to different temperature and soil moisture treatments. We determined delta C-13(R) with an in-tube incubation technique and d13CRS with compound-specific isotope analysis during a daily cycle. The highest delta C-13(R) values were found in the organic acid malate under different environmental conditions, showing less negative values compared to delta C-13(R) (up to 5.2%) and compared to delta C-13(R) of soluble carbohydrates, citrate and starch (up to 8.8%). Moreover, linear relationships between delta C-13(R) and delta C-13(RS) among different putative carbon sources were strongest for malate during daytime (r2= 0.69, P= 0.001) and nighttime (r(2)= 0.36, P= 0.001) under all environmental conditions. A multiple linear regression analysis revealed delta C-13(RS) of malate as the most important carbon source influencing delta C-13(R). Thus, our results strongly indicate malate as a key carbon source of C-13 enriched dark-respired CO2 in potato plants, probably driven by an anapleurotic flux replenishing intermediates of the Krebs cycle.
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