Work

Blue light optimizes photosynthetic physiology and photoprotective molecular mechanisms of Hydrangea quercifolia seedlings

Year: 2026

Type: article

Abstract: Introduction Hydrangea quercifolia is a rare ornamental shrub whose natural populations have declined due to habitat loss, necessitating efficient artificial propagation techniques. Light quality is a critical environmental factor regulating seedling growth and physiological quality; however, the molecular mechanisms by which different LED light spectra modulate photosynthetic physiology and hormone signaling in H. quercifolia remain poorly understood. Methods We investigated the regulatory mechanisms of four LED light qualities—white (W), blue (B), red (R), and red:blue = 3:1 (R3B1)—on the growth, photosynthetic performance, chloroplast ultrastructure, hormone metabolism, and transcriptomic profiles of H. quercifolia 'Harmony' seedlings. Physiological parameters were measured on days 7, 14, and 21, and RNA sequencing was performed to identify differentially expressed genes and associated signaling pathways. Results Blue (B) light significantly increased chlorophyll, anthocyanin, and cytokinin (CTK) contents, promoted chloroplast proliferation and grana thylakoid development, and enhanced photosynthetic efficiency. Transcriptomic analysis revealed that B light upregulated genes encoding photosystem I (PSI) and photosystem II (PSII) reaction center proteins (especially PsbS , Photosystem II S subunit), strengthened non-photochemical quenching (NPQ) and photoprotective capacity, and reduced brassinosteroid (BR) biosynthesis by suppressing BRI1 (Brassinosteroid Insensitive 1) and BSK (Brassinosteroid-Signaling Kinase) expression. In contrast, R3B1 and red (R) light induced chloroplast shrinkage, reduced chloroplast number, and triggered starch accumulation. R3B1 light inhibited PSII oxygen evolution and electron transport, downregulating chloroplast-related genes; while R light suppressed cytokinin biosynthesis by downregulating CRE1 (Cytokinin Response 1) and activated BAK1 (BRI1-Associated Receptor Kinase 1)-mediated BR signaling. Discussion These findings demonstrate that blue light plays a pivotal role in promoting the high-quality development of hydrangea seedlings by optimizing photosynthetic apparatus assembly, enhancing photoprotection, and repressing BR-mediated growth inhibition. The differential molecular responses to distinct light spectra provide a theoretical basis for designing optimized artificial light environments and improving the efficiency of horticultural seedling production.

Source: Frontiers in Plant Science

DOI: 10.3389/fpls.2026.1951910

Authors: Pengfei Su, Dacheng Wang, Yameng Gao, Xue Chen, Jinyan Hou, Lifang Wu