Analysis Of Light Quality、Light Intensity Response And Metabolite Difference In Seedling Stage Of Industrial Hemp

Illumination is one of the important environmental factors affecting plant growth and development.Many crops have been produced with high quality and efficient under the control of artificial light source.The research of using LED as energy saving light source to regulate plant growth has always been the focus of exploring to perfect plant factory cultivation.As a commercial crop,Cannabis sativa L.has high utilization value in fiber and metabolite.In order to improve its economic efficiency,indoor cultivation is an indispensable cultivation mode with open field cultivation,but there are few reports on the response of industrial hemp to light conditions.In order to provide the theoretical basis for the indoor cultivation of industrial hemp,In this study,two legally cultivated industrial hemp varieties’Longdama 3’（the representative variety of Heilongjiang Province）and’Yunma 1’（the representative variety of Yunnan Province）were selected as samples,LED lamp as the light source,set the combination of red（R）:blue（B）:white（W）=3:3:1,red（R）:blue（B）:white（W）=9:3:1,red（R）:blue（B）:white（W）=1:0:0,red（R）:blue（B）:white（W）=1:0:3,and set four different light intensity on the basis of screening the optimal combination:weak light of 30μmol·m^-2·s^-1,medium weak light of 80μmol·m^-2·s^-1,medium high light of 130μmol·m^-2·s^-1,high light of 180μmol·m^-2·s^-1.The agronomic traits,SPAD value,soluble sugar content,soluble protein content,free amino acid content and activities of antioxidant enzymes（SOD,POD,CAT）were determined at seedling stage.Wide-target metabolomics analysis was performed on the two cultivars under different light intensity fractions based on UPLC-MS/MS metabolomics technique.The main results are as follows:1.Red:blue:white=1:0:3 was the best combination of light quality for the growth of industrial hemp seedlings.In red:blue:white=1:0:3 processing under two kinds of industrial hemp plant height,stem diameter,aboveground fresh weight and dry weight,fresh weight and dry weight of underground part are the highest,SPAD value,antioxidant enzyme activity,soluble osmotic regulation substances content overall is higher,MDA content was low.compared with monochromatic red light,it decreased by 62.15%（Longdama 3）and 47.44%（Yunma 1）.2.130μmol·m^-2·s^-1was the most suitable for the growth of two kinds of hemp.The plant height of Longdama 3 increased with decreasing light intensity,and that of Yunma 1increased first and then slightly decreased with decreasing light intensity,and reached the highest value at 130μmol·m^-2·s^-1.180μmol·m^-2·s^-1could inhibit the increase of plant height of two kinds of hemp.The stem diameter of the two kinds of industrial hemp increased firstly and then decreased with the decrease of light intensity,and reached the maximum at 130μmol·m^-2·s^-1.Leaf fresh weight,dry weight,stem fresh weight and dry weight increased with decreasing light intensity,and reached the highest value at130μmol·m^-2·s^-1.Root fresh weight and dry weight decreased with decreasing light intensity,and reached the highest value at 180μmol·m^-2·s^-1.Leaf fresh weight and dry weight,stem fresh weight and dry weight,root fresh weight and dry weight increased with decreasing light intensity,and reached the highest value at 130μmol·m^-2·s^-1.The SPAD value of Longdama 3 increased first and then decreased with the decrease of light intensity,and reached the highest value at 130μmol·m^-2·s^-1.The SPAD value of Yunma 1increased with the decrease of illumination.3.The soluble sugar content was positively correlated with light intensity,while the soluble protein and free amino acid content was negatively correlated with light intensity.The activities of SOD,POD and CAT increased first and then decreased with the decrease of light intensity,and reached the peak value at 130μmol·m^-2·s^-1.The content of MDA decreased firstly and then increased with the decrease of light intensity,and the accumulation of MDA was the lowest at 130μmol·m^-2·s^-1,and the highest at30μmol·m^-2·s^-1.Comprehensive analysis showed that 130μmol·m^-2·s^-1was the most suitable for normal physiological metabolism of the two kinds of industrial hemp.4.A total of 693 metabolites were detected by metabolome analysis.Including 81kinds of amino acid and its derivatives,110 kinds of phenolic acid compounds,47nucleotide and its derivatives,91 kinds of flavonoids,eight kinds of wooden fat element compounds,9 kinds of coumarin compounds,43 kinds of sugar and alcohol compounds,2kinds of stilbene compounds,17 kinds of vitamin compounds,6 kinds of tannins compounds,50 kinds of alkaloids compounds,6 terpenoids,64 organic acids,120 lipids,17 cannabinoids and 20 other compounds were identified.The differential metabolites were mainly phenolic acid metabolites,flavonoid metabolites,sugar and alcohol metabolites,organic acid metabolites,amino acids and their derivatives,nucleotide and their derivatives,and lipid metabolites.Based on the overall metabolome analysis,The highest concentration of metabolites accumulated in industrial hemp was 130μmol·m^-2·s^-1.Low light was not conducive to the accumulation of metabolites in industrial hemp.With the decrease of light intensity,amino acids and their derivatives were significantly up-regulated,while phenolic acids,flavonoids,sugars and alcohols,organic acids and lipid metabolites were significantly down-regulated.The common difference metabolites between different light intensities were mainly phenolic acid metabolites,flavonoids metabolites,sugar and alcohol metabolites,organic acid metabolites,amino acids and their derivatives,nucleotides and their derivatives.There are a lot of metabolites which have important influence on plant growth and development.5.Different light intensity has different effects on metabolic pathways in industrial hemp.Longdama 3 significant differences in metabolic pathway of enrichment of concentrated in the galactose metabolism,flavonoids biosynthesis,amino acid biosynthesis and metabolism,pentose and glucuronate interconversions,amino sugar and nucleotide sugar metabolism,stilbenoid,diarylheptanoid and gingerol biosynthesis,photosynthesis,indole alkaloid biosynthesis,riboflavin metabolism,pentose phosphate pathway,starch and sucrose metabolism,glutathione metabolism;Yunma 1 significant differences in metabolic pathway of enrichment of amino sugar and concentrated in the pentose phosphate pathway,amino sugar and nucleotide sugar metabolism,flavonoids biosynthesis,pyruvate metabolism,the Krebs cycle,nicotinate and nicotinamide metabolism,galactose metabolism,amino acid biosynthesis and metabolism,photosynthetic carbon fixation,taurine and low taurine metabolism,stilbenoid,diarylheptanoid and gingerol biosynthesis,thiamine metabolism.