The synergistic effect of grafting and LED light quality on enhancing the mineral nutrition and growth performance of tomato seedlings

Light quality is a critical determinant in controlled environment agriculture, yet information regarding the interactive effects of spectral composition and grafting on tomato seedling performance remains limited. Moving beyond the assumption that rootstock vigor is solely a static trait, we hypothesized that above-ground spectral cues significantly modulate rootstock efficiency. We investigated the synergistic effects of grafting (Solanum lycopersicum 'Maxifort') and various LED spectra (monochromatic Red, Blue, White, and Red:Blue 70:30) on morphological architecture, photosynthetic potential, and the stoichiometric balance of mineral nutrients in tomato seedlings. Our results reveal a critical interaction: while grafting alone alleviated specific nutritional deficits (N, K, Mg) under suboptimal monochromatic red light, the rootstock's capacity to maximize the uptake of key elements-particularly phosphorus and calcium-was fully realized only under the synergistic Red:Blue spectrum. This study provides empirical evidence that integrating the R70:B30 spectrum with grafting not only improves growth but also optimizes resource acquisition. These findings offer a novel approach to optimizing transplant quality and establish a robust protocol for producing resilient transplants in modern nurseries. Future research should focus on unraveling the molecular pathways underlying this light-rootstock communication.