Monochromatic Light Orchestrates Integrated Transcriptomic and Metabolic Reprogramming to Alleviate Phosphorus Starvation in Banana (Musa spp.)

Phosphorus (Pi) deficiency limits plant productivity. Light quality modulates growth and stress responses, but its interaction with Pi starvation in banana is unclear. We investigated physiological, transcriptomic, and metabolomic responses of banana seedlings to low Pi under white (WL), red (R), far-red (FR), blue (B), and ultraviolet (UV-A) light. FR light promoted shoot elongation and increased phosphorus, iron, and calcium accumulation, whereas B and UV-A exacerbated growth inhibition and oxidative stress (higher H2O2, MDA, and proline). Transcriptomics revealed that B and UV-A enriched cell cycle and stress pathways, while FR enriched photosynthesis and cell wall biogenesis. Expression of phosphate transporters and starvation-responsive genes was spectrum-specific. Metabolomics showed B and UV-A triggered massive accumulation of ABA, flavonoids, and secondary metabolites, indicating strong stress defense. Antioxidant enzyme activities were differentially activated: B upregulated SOD, CAT, and POD; UV specifically enhanced GSH-Px. Integrated correlation networks revealed distinct regulatory hubs: blue light centered on ROS scavenging, red light on phosphate transport. Our findings demonstrate that FR light acts as a positive regulator, while B and UV-A act as additional stressors under Pi deficiency, providing a mechanistic framework for using light spectra to improve crop resilience in Pi-limited conditions.