Natural ¹³C distribution in oil palm (Elaeis guineensis Jacq.) and consequences for allocation pattern

Oil palm has now become one of the most important crops, palm oil representing nearly 25% of global plant oil consumption. Many studies have thus addressed oil palm ecophysiology and photosynthesis-based models of carbon allocation have been used. However, there is a lack of experimental data on carbon fixation and redistribution within palm trees, and important C-sinks have not been fully characterized yet. Here, we carried out extensive measurement of natural ¹³C-abundance (δ¹³C) in oil palm tissues, including fruits at different maturation stages. We find a ¹³C-enrichment in heterotrophic organs compared to mature leaves, with roots being the most ¹³C-enriched. The δ¹³C in fruits decreased during maturation, reflecting the accumulation in ¹³C-depleted lipids. We further used observed δ¹³C values to compute plausible carbon fluxes using a steady-state model of ¹³C-distribution including metabolic isotope effects (¹²v/¹³v). The results suggest that fruits represent a major respiratory loss (≈39% of total tree respiration) and that sink organs such as fruits are fed by sucrose from leaves. That is, glucose appears to be a quantitatively important compound in palm tissues, but computations indicate that it is involved in dynamic starch metabolism rather that C-exchange between organs.