Integrated physiology, metabolic, and transcriptomics studies provide new insights into the effects of different light conditions on tomato drought tolerance

• RB light alleviates drought damage and optimizes plant architecture in tomato. • Enhanced antioxidant and osmotic regulation under RB. • RB upregulates flavonoid biosynthesis genes ( CHS, CHI, F3H ) and metabolites. • MYB co-regulate light-induced flavonoid accumulation under drought. Tomato ( Solanum lycopersicum L.) is an economically important crop, but drought stress severely affects its growth and yield. While studies on the effects of different light qualities on plant responses to abiotic stress are abundant, the specific mechanisms in tomatoes remain unclear. Here, physiological, metabolomic, and transcriptomic data were integrated to investigate how the quality of red-blue light influences drought tolerance in tomato seedlings. The results indicated that red light (R), blue light (B), and red-blue composite light (RB) significantly mitigated drought-stress damage and optimized the structure of leaves, stems, and root systems compared to white light (CK). The RB treatment enhanced plant tolerance by boosting antioxidant and osmotic regulation capacities, thereby suppressing the accumulation of malondialdehyde (MDA) and reactive oxygen species (ROS) while improving water use efficiency. Metabolomic and transcriptomic analyses revealed that the expression of flavonoid biosynthesis genes, including CHS, CHI , and F3H increased promoted the accumulation of flavonoids was increased in tomato seedling leaves with RB treatment under drought stress. Furthermore, transcription factors, particularly members of the MYB family, were identified as crucial regulators in the flavonoid biosynthesis pathway. This study reveals that red-blue composite light significantly enhances tomato seedling drought tolerance by synergistically regulating antioxidant defense systems and flavonoid biosynthesis, providing crucial insights for optimizing light quality in tomato cultivation under drought stress conditions.