Abstract: In this study, nine types of lettuce with different leaf color and leaf shape were selected in this experiment, the light source was set up with compound light whose ratio of red and blue composite light was 7:1, and the contrast experiment was carried out with white light in plant factory. The results showed that compared to the white light (WL) treatment, red and blue (RBL) composite light enhanced the relative growth rate of plant height of green leaf lettuce (P < 0.05), but inhibited its overgrowth, and decreased the chlorophyll content of purple lettuce the net photosynthetic large rate, transpiration rate and stomatal conductance of half-enveloped and loose-leaf lettuce varieties were increased (P < 0.05). The maximum photochemical efficiency of PSⅡ of all varieties of lettuce was inhibited. The ETR value of loose-leaf lettuce varieties was increased (P < 0.05); The soluble solid content and soluble sugar content of half-headed lettuce were increased (P < 0.05); The content of vitamin C, yield and dry matter rate of green loose-leaf lettuce were increased (P < 0.05). In a word, the effect of red and blue composite light on the growth, development and photosynthetic fluorescence characteristics of different lettuce varieties was mainly related to the degree of leaf dispersion, the effect of improving the quality and yield of green lettuce was better than that of purple lettuce.

Key words: Red and blue light, Varietal variation, Growth and development, Photosynthetic fluorescence, Quality and yield