Lycopene, one of the strongest natural antioxidants known and the main carotene in ripe tomato, is very important for human health. Light is well known to be one of the most important environmental stimuli influencing lycopene biosynthesis; specifically, red light induces higher lycopene content in tomato. However, whether blue light promotes lycopene synthesis remains elusive and exactly how light stimulation promotes lycopene synthesis remains unclear. We applied supplemental blue and red lighting on tomato plants at anthesis to monitor the effect of supplemental blue and red lighting on lycopene synthesis. Our results showed that supplemental blue/red lighting induced higher lycopene content in tomato fruits; furthermore, we found that the expression of key genes in the lycopene synthesis pathway was induced by supplemented blue/red light. The expression of light signaling components, such as red-light receptor phytochromes (PHYs), blue-light receptor cryptochromes (CRYs) and light interaction factors, phytochrome-interacting factors (PIFs) and ELONGATED HYPOCOTYL 5 (HY5) were up-or down-regulated by blue/red lighting. Thus, blue and red light increased lycopene content in tomatoes by inducing light receptors that modulate HY5 and PIFs activation to mediate phytoene synthase 1 (PSY1) gene expression. These results provide a sound theoretical basis for further elucidation of the light regulating mechanism of lycopene synthesis in tomatoes, and for instituting a new generation of technological innovations for the enhancement of lycopene accumulation in crop production.

To evaluate the supplementary blue light intensity on growth and health-promoting compounds in pak choi (Brassica campestris ssp. chinensis var. communis), four blue light intensity treatments (T0, T50, T100 and T150 indicate 0, 50, 100, and 150 μmol m-2 s-1 , respectively) were applied 10 days before harvest under greenhouse conditions. Both of cultivars (greenand red-leaf pak choi) under T50 had the highest yield, content of chlorophyll and sugars. With light intensity increasing, antioxidant compounds (vitamin C and carotenoids) significantly increased, while nitrate content showed an opposite trend. The health-promoting compounds (phenolics, flavonoids, anthocyanins, and glucosinolates) were significantly higher under supplementary light treatment than T0, so as the antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl and ferric-reducing antioxidant power). The species-specific differences in photosynthetic pigment and health-promoting compounds was found in green-and red-leaf pak choi. T50 treatment could be used for yield improvement, whereas T100 treatment could be applied for quality improvement. Results showed that blue light intensity can regulate the accumulation of biomass, morphology and health-promoting compounds in pak choi under greenhouse conditions.