%A %T Effects of High Light Duration and Frequencies on Growth and Nutrient Element Contents of Hydroponic Lettuce Cultivated Under LED Red and Blue Light %0 Journal Article %D 2021 %J SPECTROSCOPY AND SPECTRAL ANALYSIS %R 10.3964/j.issn.1000-0593(2021)09-2853-06 %P 2853-2858 %V 41 %N 09 %U {https://www.gpxygpfx.com/CN/abstract/article_12223.shtml} %8 2021-09-01 %X As the largest band of light absorption of plant photosynthetic pigment, the red and blue spectrum is the main function spectrum of plant photosynthesis, and red-blue LED has become the mainstream light source of plant factories. The response of plants to red-blue light and its mechanism needs to be explored. In this study, effects of high light duration and alternating frequencies of high light supplied with red-blue LEDs on growth and nutrient element content as well as accumulation of hydroponic lettuce were conducted using ICP-AES analysis technology in an artificial plant factory. Five treatments were set up in experiment 1: high light (500 μmol·m-2·s-1) was irradiated for 0 h (CK), 0.5 h (HL0.5), 1 h (HL1), 2 h (HL2) and 4 h (HL4) in the middle of the light period (150 μmol·m-2·s-1), respectively. In experiment 2, set up one conventional treatment (NL, 170 μmol·m-2·s-1) and four alternate light treatments, in which 1 h high light was separated into four different alternating frequencies: one time (A1), three times (A3), six times (A6) and twelve times (A12). The light quality (4R∶1B), photoperiod (16/8 h), and treatment days (20 days) were the same in the two experiments. The results showed that the biomass production and the accumulation of nutrients of lettuce such as N,C,P,K,Ca,Mg increased first and then decreased with the increase of high light duration. Compared with the CK, the root dry and fresh weight, and specific leaf weight of lettuce grown under HL4, increased significantly, and the leaf area decreased significantly. The dry weight of lettuce and the accumulation of N,C,P,K,Ca and Mg were the highest under HL2. Compared with NL treatment, A6 significantly reduced the fresh weight and increased the root shoot ratio of lettuce, but there was no significant difference among other treatments. The alternating light treatments significantly increased the C element content of lettuce, but the alternating frequencies of high light had no significant effect on the biomass production and the accumulation of nutrient elements. In conclusion, applying a short-term continuous high light irradiation in the middle of the light period can effectively improve the accumulation of nutrients and biomass production in lettuce and is more suitable for lettuce cultivation in plant factories.