Metabolic dynamics of oil palm seed during germination: effects of storage duration

Oil palm (Elaeis guineensis Jacq.) is the world's leading vegetable oil crop in terms of oil production, with about 23 million ha of plantations. Maintenance of such a considerable surface area requires replanting of millions oil palm seedlings each year. Yet, producing oil palm germinated seeds remains slow and difficult, due to morphological and physical dormancies. Different techniques are being used to improve germination rates, amongst which the dry heat treatment is the most popular. However, the germination rate remains variable and depends on palm crosses, environmental conditions and most importantly, seed storage duration. To better understand biochemical events in germination and how seed ageing affects them, we conducted a metabolomics analysis of oil palm seeds during germination, using NMR and GC-MS techniques. We characterized metabolic changes in different tissues (embryo, endosperm, and haustorium) at several germination stages (from day 0 to 116), using seeds stored for either 4 or 16 months. As expected, germination was associated with early protein remobilization, sugar interconversions, stored lipid remobilization and biosyntheses to support early heterotrophic growth. Multivariate analyses show that metabolic trajectories were strongly influenced by both time (development stage) and storage duration. Storage duration affected lipid and protein metabolism differentially in embryo and endosperm. Furthermore, seeds that did not germinate also had tissue-specific metabolic patterns depending on whether they were stored for 4 or 16 months, suggesting that metabolic bottlenecks responsible for the developmental arrest changed with storage duration.