Metabolism is a major driver of hydrogen isotope fractionation recorded in tree-ring glucose of Pinus nigra

Abstract

- Stable isotope abundances convey valuable information about plant physiological processes and underlying environmental controls. Central gaps in our mechanistic understanding of hydrogen isotope abundances impede their widespread application within the plant and Earth sciences. - To close these gaps, we analysed intramolecular deuterium abundances in glucose of Pinus nigra extracted from an annually resolved tree-ring series (1961 to 1995). - We found fractionation signals at glucose H1 and H2 introduced by closely related metabolic processes. These signals (and thus metabolism) respond to drought and atmospheric CO2 concentration beyond a response change point. They explain ≈60% of the whole-molecule deuterium variability. Altered metabolism is associated with below-average yet not exceptionally low growth. - We propose the signals are introduced at the leaf-level by changes in sucrose-to-starch carbon partitioning and anaplerotic carbon flux into the Calvin-Benson cycle. In conclusion, metabolism can be the main driver of hydrogen isotope variation in plant glucose.

Anaplerotic flux into the Calvin-Benson cycle. Hydrogen isotope evidence forin vivooccurrence in C3metabolism

“…Second, Wieloch et al . (2021) also analysed intramolecular deuterium (D) abundances across the Pinus nigra tree-ring series.…”

“…Metabolites: 3PGA, 3-phosphoglycerate; 6PG, 6-phosphogluconate; 6PGL, 6-phosphogluconolactone; ATP, adenosine triphosphate; F6P, fructose 6-phosphate; G6P, glucose 6-phosphate; NADPH, nicotinamide adenine dinucleotide phosphate; Ru5P, ribulose 5-phosphate; RuBP, ribulose 1,5-bisphosphate; TP, triose phosphates (glyceraldehyde 3-phosphate, dihydroxyacetone phosphate). Modified figure from Wieloch et al . (2021).…”

“…Interestingly, the response requires the crossing of a change point. Allegedly, shifts of the chloroplastic PGI reaction towards equilibrium contribute to the signal at H 2 while chloroplastic G6PD contributes to the H 1 signal as anaplerotic flux increases (Wieloch et al ., 2021).…”

“…(2021) reported evidence for anaplerotic flux under normal growth conditions while Wieloch et al . (2018, 2021) reported evidence for stress-induced upregulation.…”

“…To explain the 13 C and D fractionation signals observed in tree-ring glucose of the gymnosperm Pinus nigra , Wieloch et al . (2021) proposed the following hypotheses.…”