Effects of LED spectrum combinations on the absorption of mineral elements of hydroponic lettuce

Lettuce(Lactuca sativa)was hydroponically cultured in a completely enclosed plant factory,in which spectrum proportion-adjustable LED panels were used as sole light source for plant growth.Absorption and content of eleven mineral elements such as K,P,Ca,Mg,Na,Fe,Mn,Zn,Cu,B and Mo in Lactuca sativa under different spectral component conditions were studied by ICP-AES technology.The results showed that:(1)Single or combined spectrums corresponding to the absorbing peaks of chlorophyll a and b(450,660nm)could enhance the absorbing ability of roots especially for mineral elements Na,Fe, Mn,Cu and Mo,the single red spectrum had the most significant promoting effect under which contents of those four elements were respectively 7.8,4.2,4.0and 3.7times more than that under FL;(2)Absorption of K and B was the highest under FL which was 10.309mg·g-1 and 32.6μg·g-1 while the values decreased significantly under single or combined spectrum of red and blue;(3)Plants grown under single blue spectrum had the lowest absorption of Ca and Mg which respectively decreased by 35% and 33%than FL;(4)Lettuce grown under the spectrum combination of 30%blue and 70%red had the highest accumulations of biomass while those grown under 20% blue and 80%red had the highest accumulations of the following seven elements Ca,Mg,Na,Fe,Mn,Zn and B.The results provided theoretical basis for adjusting nutrient solution formula and selecting light spectrum of hydroponic lettuce.