Abstract:

The LED as precision modulation light sources were used with 3 treatments including red（R）light，blue（B）light and combination of red and blue light with proportion of 3︰1（3R1B），white light as control. The effects of red and blue light qualities on main fruit quality and gene expression of key enzymes involved in the biosynthesis of lycopene of tomato with‘Micro-Tom’as experiment material during color-turning period were studied. The results showed that compared with control，red and 3R1B light treatment could significantly increase the soluble sugar content and ratio of sugar and acid in tomato fruit，but reduced the titratable acid content. The content of vitamin C，soluble protein and titratable acid under blue light was significantly enhanced，while lower in the soluble sugar content and no significant difference was found compared with control. With the fruit maturation，the lycopene content and gene expression of geranylgeranyl pyrophosphate synthase（GGPS）and phytoene synthase（PSY）were significantly higher under red and 3R1B light than those under blue and white light，especially for 3R1B. Furthermore，the lycopene content was significantly reduced and the expression of GGPS and PSY1 was inhibited by blue light. In summary，blue light could promote the increment in levels of vitamin C，protein and organic acids. Red and combination of red and blue light were more conducive to the accumulation of carbohydrates，and promoted lycopene synthesis by enhancing the transcription levels and activities of GGPS and PSY1，which involved in the biosynthesis of lycopene，especially the latter treatment. It indicated that the combination of red and blue light with appropriate proportion could promote the color-turning of tomato fruit and improve fruit quality.

Key words: tomato, lycopene, light-emitting-diode, light quality, fruit quality