Abstract: The study investigated the effects of light qualities on seed germination and seedling growth of lettuce. Plants were grown under six different combinations of red and blue light (2R/1B， 4R/1B， 8R/1B， 1R/2B， 1R/4B， 1R/8B). The results showed that different light qualities had different influences on seed germination and seedling growth of lettuce. The combination of red (R) and blue (B) lights based on red promoted seed germination obviously， and the germination potential， germination index and vigor index under these treatments were significantly higher than those of control. Compared with seedlings grown under white light， the mixture of blue and red light promoted the morphogenesis， root activity， content of leaf pigment and chlorophyll fluorescence of lettuce seedlings. Furthermore， the promoting effects under the RB lights based on red were better than those of treatments based on blue. The combination of 2R/1B and 4R/1B were better than the combination of 8B/1R on promoting seed germination and seedling growth in lettuce. These results indicated that light quality significantly affected the seed germination and seedling growth of lettuce， and the treatments of 2R/1B and 4R/1B showed more superiority than others．

Key words: Lactuca sativa L., light quality, seed germination, growth