Blue:red LED ratios coordinate pigment accumulation and vacuolar pH to reshape petal color and VOC profiles in Rosa hybrida 'Juicy Terrazza'.

BACKGROUND

Light quality is a controllable signal in protected horticulture that can shift rose petal color and scent. However, how defined blue:red (B:R) ratios jointly influence pigment composition, vacuolar pH, and volatile organic compounds (VOCs) across development remains not fully understood.

RESULTS

Rosa hybrida 'Juicy Terrazza' plants were grown under six LED spectra (CK, B, R, 1B1R, 1B2R, 2B1R) in a randomized complete block design (RCBD; n = 3 blocks). A moderately blue-enriched spectrum (2B1R) increased late-stage yellowness (b*) and carotenoid accumulation at S4, whereas red and red-biased spectra favored anthocyanin accumulation. Vacuolar pH differed among treatments at S3-S4 and showed associations with color coordinates. VOC profiling at S4 within a fixed sampling window revealed spectrum-dependent compositional shifts, including enrichment of apocarotenoid-related volatiles under 2B1R. Transcript analyses showed stage-dependent regulation of flavonoid and carotenoid pathway genes, with the largest treatment divergence at S2.

CONCLUSIONS

Defined B:R ratios reshape warm-toned rose traits through coordinated changes in pigment pools, vacuolar pH, and, at S4, VOC profiles, supporting spectral strategies that target specific developmental windows to optimize ornamental quality.