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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.

Light and nutrient are important factors for vegetable production in plant factory or greenhouse. The total 12 treatments which contained the combination of four light intensity (150, 250, 350 and 450 μmol · m −2 · s −1 ) and three nutrient solution concentration (NSC) (1/4, 1/2, 3/4 strength NSC) were established for investigation of lettuce growth and quality in a growth chamber. The combination of light intensity and NSC exhibited significant effects on photosynthetic pigment, nutritional quality, mineral content and antioxidant capacity. That a higher light intensity were readily accessible to higher chlorophyll a/b showed in lettuce of treatment of 350 μmol · m −2 · s −1 × 3/4NSC and 450 μmol · m −2 · s −1 × 1/4NSC. Lower total N contents, higher content of soluble protein, vitamin C, soluble sugar and free amino acid exhibited in lettuce under treatment of 250 and 350 μmol · m −2 · s −1 × 1/4NSC or 3/4NSC. With increasing NSC and LED irradiance, the content of total P and K in lettuce increased and decreased, respectively. The highest and lowest total Ca content were found in treatment of 150 μmol · m −2 · s −1 × 1/4NSC and 450 μmol · m −2 · s −1 × 1/4NSC, respectively, and higher content of total Mg and Zn was observed under 250 μmol m −2 s −1 × 1/4NSC and 150 μmol · m −2 · s −1 × 3/4NSC, respectively. The antioxidant contents generally decreased with increasing NSC level. The higher antioxidant content and capacity occurred in lettuce of 350 μmol · m −2 · s −1 × 1/4NSC treatment. The interaction of 350 μmol · m −2 · s −1 × 1/4NSC might be the optimal condition for lettuce growth in plant factory.Lettuce (Lactuca sativa L.) is one of the most important vegetable in the world, which is main crop in plant factory. The secondary metabolite in vegetable plays key roles for human body health, such as phenolic compound, vitamin A and C, and carotenoid. These compounds have a function on nutrition and health care 1 , which could enhance anti-oxidation ability of human body, and the suppression of inflammatory disease and cancer 2,3 . Nutritional quality of lettuce is affected by light and nutrient solution in plant factory. Light (including light quality, intensity and photoperiod) plays a crucial role in improvement of plant nutrition quality 4,5 . The proper ratio of red and blue light is essential for plant growth and development 6 . Light intensity not only positively regulates lettuce biomass and morphology, but also nutrition quality and activities of anti-oxidative enzymes 7,8 . The content of soluble sugars and ascorbic acid in lettuce increases with increasing light intensity 9 . Different light intensity is required by different plant for nutritional quality and growth. The highest content of lutein, ß-carotene and chlorophyll in leave shows at 335 μmol · m −2 · s −1 for kale, but 200 μmol · m −2 · s −1 for spinach 10 . In ten leafy vegetables (chicory, green lettuce, lamb's lettuce, mizuna, red chard, red lettuce, rocket, spinach, swiss chard, and tatsoi), higher leaf dry matter, content of protein, K,...

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.

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