Modified white LEDs spectra alter tomato seedling quality and post-transplant responses

This study evaluated tomato ( Solanum lycopersicum L.) seedling responses to three white-light-emitting diodes (LEDs) spectra and assessed post-transplant performance in a commercial greenhouse. The treatments were normal white light (NW), normal white light supplemented with red light (NWR), and a specific white-plus-red spectrum (SWR). All treatments delivered 275 ± 5 µmol m −2 s −1 for 20 d, with blue emission peaks at 450 nm in NW and NWR and 436 nm in SWR. Relative to NW, SWR increased leaf fresh and dry weights, leaf number, leaf area, and compactness. Red-containing treatments had lower sucrose and higher glucose relative peak abundances than NW. RT-qPCR revealed gene-specific responses: PsbB and PsaB transcript levels were higher under SWR than under NW and NWR, whereas RbcL and RbcS transcript levels did not differ among treatments. After transplanting, net photosynthetic rate did not differ among treatments at 40, 54, 68, or 82 d after transplanting (DAT). Cumulative fruit yield was higher under SWR at 78 DAT, but final cumulative yield at 127 DAT did not differ among treatments. Soluble-solids and lycopene responses were trait specific. Under the tested conditions, the SWR composite spectrum improved selected seedling-quality traits and was associated with a transient early-yield response, but it did not increase final cumulative yield.