Study on the Influence of Different Far Red Light intensity on Growth, Photosynthetic Characteristics and Quality of Lettuce

Abstract

<b><sc>Abstract.</sc></b> In order to investigate effect of far red light on the yield and quality of hydroponic lettuce in artificial light plant factories, under the condition of 200 μmol·m^-2·s^-1 of photosynthetic effective radiation intensity, white LED was used as CK treatment, and two far red treatments(TM1 and TM2 treatment) were set by adding 10 μmol·m^-2·s^-1 and 20 μmol·m^-2·s^-1 far red light on the basis of CK, respectively, and the growth and development, photosynthetic characteristics and nutritional quality of plant treated with different light quality combinations were studied. The results showed that compared with CK treatment, the plant heights of TM1 and TM2 treatments significantly increased by 10.88% and 8.22%, respectively; The max leaf area of TM1 and TM2 treatments significantly increased by 33.13% and 38.29%, respectively; the root length of TM1 treatment significantly increased by 28.75%; the lettuce biomass of TM1 and TM2 treatments were significantly increased. TM1 and TM2 treatments reduced leaf chlorophyll content, chlorophyll a/b value and net photosynthetic rate, while improved the ability of plant to capture light, which was benefit to accumulation of dry matter in lettuce. Different far red light intensity had different effects on the quality indicators of plant. The contents of soluble sugar, soluble protein and vitamin C in the leaves of TM2 treatment significantly increased by 22.13%, 37.47% and 21.36%, respectively. Compared with CK, the nitrite content of plant leaves in TM1 and TM2 treatments significantly reduced by 23.67% and 24.02%, respectively. Adding 20 μmol·m^-2·s^-1 far red light on the basis of the white LED in the plant factory can effectively improve the yield and quality of lettuce. This study is expected to provide theoretical reference for application of far red light in the plant factory.