Unraveling the response of secondary metabolites to cold tolerance in oil palm by integration of physiology and metabolomic analyses.

Abstract

Background: Oil palm (Elaeis guineensis), a tropical crop, is highly sensitive to temperature fluctuations, with low temperatures significantly limiting its growth, development, and geographical distribution. Understanding the adaptive mechanisms of oil palm under low-temperature stress is essential for developing cold-tolerant varieties. This study focused on analyzing the physiological and metabolomic responses of annual thin-shell oil palm seedlings to low-temperature exposure (8 °C) for different time periods: 0 h (CK), 0.5 h (CD05), 1 h (CD1), 2 h (CD2), 4 h (CD4), and 8 h (CD8).

Results: Physiological analysis showed a significant increase in the activity of antioxidant enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), highlighting the activation of oxidative stress defense mechanisms. Concurrently, elevated relative conductivity, indicated cell membrane damage, a common consequence of cold-induced oxidative stress. Metabolomic profiling using LC-MS/MS revealed significant changes in metabolite composition, with differential metabolites predominately enriched in key metabolic pathways such as arginine and proline metabolism, glycine, serine, and threonine metabolism, plant hormone biosynthesis, and flavonoid biosynthesis pathways. Notable metabolites such as citric acid, L-aspartic acid, L-tryptophan, and vitexin showed significant accumulation, indicating their roles in enhancing cold tolerance through improved antioxidant defenses, promoting osmoregulation, and stabilizing cellular structures. Correlation analysis further emphasized the importance of flavonoids and plant hormones in the cold stress response. In particular, vitexin, isovitexin, and apigenin 6-C-glucoside were significantly enriched, suggesting their contribution to antioxidant and stress signaling networks. Furthermore, metabolites involved in amino acid metabolism, including L-glutamic acid, sarcosine, and proline, were upregulated, supporting enhanced protein synthesis and cellular repair under stress. This metabolic reprogramming correlated with physiological improvements, as evidenced by increased relative conductivity and post cold exposure growth recovery.

Conclusion: This study provides critical insights into the physiological and metabolic adaptations of oil palm to cold stress, emphasizing the significant role of secondary metabolites-such as flavonoids, amino acids, and plant hormones-in enhancing cold tolerance. Theses metabolites contribute to oxidative stress protection, osmotic regulation, and cell wall stabilization enabling the plant to better withstand with low temperature condition. The findings provide a strong foundation for molecular research and breeding initiatives aimed at developing cold tolerant oil palm varieties, a crop of siginificant economic value. By combining metabolomic profiling with physiological analyses, provides a holistic understanding of the adaptive mechanisms in oil palm under cold stress.This integrated approach identifies key metabolic pathways that can be targeted in breeding programs to enhance cold resilience, paving the way for improved crop performance in challenging environments.