Responses Of Seedling Growth And Feed Nutrient Metabolism Of Hydroponic Barley In Different Light Formulas And Nitrogen Level

Artificial light hydroponic forage technology provided a new way of production to solve the shortage of green feed in animal husbandry,but low production efficiency and high energy consumption cost were the“bottleneck”in the application of this technology.The purpose of energy saving,consumption reduction and efficient production can be achieved by regulating plant growth and metabolism,increasing the biomass from crop seed germination to seedling stage through different light formulas and nitrogen application rates.In this paper,“Ganpi No.8”barley(Hordeum L.)was used as the test material,to discuss the characteristics of growth morphology,biomass,nutritional quality and metabolic transcription under different LED light quality ratio,light intensity,photoperiod and nitrogen concentration,so as to provide a scientific basis for the photosynthetic growth,physiological and biochemical mechanism of hydroponic barley.The main results were as follows:(1)Using LED red and blue light sources with different light quality ratios,six light quality ratios of B,R,R4/B,R/B,R8/B and R12/B were set.Taking no light(CK)as the control,it was concluded that the combination of red and blue light(4R/B)significantly increased the seedling leaf area,leaf length,stem,leaf and root dry matter biomass of barley.The principal component analysis of growth physiology and nutritional quality indexes of barley seedings showed that the ratio of red and blue light was 4:1.(2)Setting the light intensity to 100,200,300μmol/m~2/s,200μmol/m~2/s was beneficial to increase the contents of ether extract,crude ash,crude protein,total amino acids and essential amino acids in the stems and leaves of barley seedlings.The light intensity of 300μmol/m~2/s was beneficial to the increase of dry matter biomass and the content of crude fat,crude fiber and acid detergent fiber in root of barley plant.Higher light intensity was conducive to the increase of VC content,and VE content was the highest in the absence of light.The principal component analysis showed that the light intensity of 200μmol/m~2/s was beneficial to the growth of hydroponic barley seedlings.(3)Setting the light duration of 10,8,4,2 and 0 h in 16 h photoperiod.It was concluded that 10 h light was conducive to the growth of barley stems and leaves,the increase of amino acid content.And 8 h light was conducive to photosynthesis and dry matter mass accumulation.The chlorophyll value decreased with the decrease of illumination time.Illumination for 2 h was beneficial to increase the contents of crude protein,crude ash,crude fiber and VC.No light was conducive to the accumulation of VE content.Principal component analysis showed that 8 h/16 h was the suitable photoperiod for hydroponic barley seedlings.(4)Setting the nitrogen concentration as 0,4,8,16 mmol/L,it was concluded that nitrogen concentration of 16 mmol/L was conducive to the growth of stems and leaves of barley seedlings,biomass accumulation and photosynthesis.Nitrogen concentration of 8mmol/L was beneficial to the increase of amino acids and crude fat,crude ash and crude fiber content in stems and leaves.The nitrogen concentration of 16 mmol/L was conducive to the accumulation of crude protein and ether extract in roots.Nitrogen application reduced VE content.The content of VC was the highest when nitrogen concentration was 4 mmol/L.Principal component analysis showed that the suitable nitrogen concentration for hydroponic barley seedlings was 16 mmol/L.(5)The combined analysis of metabolism and transcriptome showed that light intensity reached 300μmol/m~2/s,the contents of aspartate,phenylalanine,glutamate,arginine,tyrosine and proline in amino acids increased,and 6 key genes regulating amino acids.The content of short chain fatty acid A increased,and 7 key genes regulated.The contents of fructose,mannose phosphate,sucrose and galactose in glucose synthesis and metabolism were different,and 6 key genes regulated;With the illumination time increasing,the contents of aspartate,glycine and arginine increased,and 6 key genes regulated.The contents of short chain fatty acid A,linoleic acid and myristic acid in fatty acids decreased,and 4 key genes regulated.Fructose content decreased significantly,and 5 key genes regulated;The application of nitrogen fertilizer increased the contents of serine,glutamate,methionine,leucine,proline and isoleucine in amino acid metabolism,and decreased the contents of phenylalanine,threonine,alanine,glycine and tyrosine.There were 6 key regulatory genes.The content of stearic acid in fatty acids decreased,and 4 key genes regulated.Fructose content decreased and sucrose increased in glucose metabolism,and 3 key genes regulated.To sum up,when hydroponics forage barley seedlings adopts LED red and blue artificial light as source,the recommended light quality ratio was R:B=4:1;The light intensity was200μmol/m~2/s;The illumination time in 16 h photoperiod was 8 h;The concentration of nitrogen nutrient solution was 16 mmol/L.The main differences and key functional genes regulating the synthesis and metabolism of amino acids,fatty acids and sugars in the growth of barley seedlings under different light intensity,photoperiod and nitrogen levels were obtained by the analysis of metabolic combined transcriptome.