Effects Of Different Light Quality And Nutrient Composition On The Growth And Tipburn Incidence Of Lettuce

Effects of different light quality and nutrient composition on the growth and tipburn incidence of lettuce (Lactuca sativa var. crispa L.) cultivated in plant factory were studied to provide the scientific guidance for the lettuce production in plant factory. Following results were obtained.Different light qualities (white fluorescent lamp, red LED, blue LED, red/blue mixed LED) had great effect on the growth and tipburn control of lettuce. With red/blue mixed LED, fresh weight, leaf number and leaf area were significantly increased, the content of nitrite was decreased, while disease index of tipburn could not be reduced. With red LED, stem elongation was promoted, disease index of tipburn and nitrate content were significantly reduced, while it was unfavorable for the accumulation of dry weight and vitamin c (Vc), and for the increase of leaf area. With blue LED, the growth of lettuce was inhibited, and nitrate content was increased, however disease index of tipburn was significantly reduced.Effeets of different potassium concentration (4 mmol·L-1,6 mmol·L-1,8 mmol·L-1,10 mmol·L-1) on the growth and tipburn control of lettuce were investigated. The fresh weight, leaf number and leaf area were significantly increased at 6 mmol·L-1 K, disease index of tipburn and nitrate content were significantly reduced, while it was unfavorable for the accumulation of Vc; disease index of tipburn was significantly reduced at 4 mmol·L-1 K, which had the highest total Ca content, the growth of the lettuce was restrained; at 10 mmol·L-1 K, disease index of tipburn was reduced and it was favorable for the accumulation of dry matter, total K and Mg content were highest. Effeets of different ratios of ammonium-N to nitrate-N (the ratios of NH+-N/NO3-N were 1:3,1:4,1:5,1:6) on the growth and tipburn control of lettuce were investigated. With the treatment of NH4+-N/NO3-N 1:5, the fresh weight, leaf number and leaf area had maximum value, and it was favorable for the accumulation of dry matter, while it was unfavorable for the accumulation of Vc, and for the decreased of nitrate content; With the treatment of NH4+-N/NO3-N 1:6, the growth of the lettuce was restrained, nitrate content was increased and Vc was reduced, disease index of tipburn was significantly reduced which had the highest total Ca content; With the treatment of NH4+-N/NO3-N 1:3, relative chlorophyll content SPAD (Soil and Plant Analyzer Development) value reached maximum, nitrate content was reduced and Vc was increased significantly, but it was unfavorable for the accumulation of dry matter and increased of tipburn disease index, total K and Mg content in leaves were highest.