Primary Mechanisms Of Blue Light Mediate The Synthesis Of Flavonoids In Soybean Sprouts

Soybean sprouts,having high medicinal value and economic value,are tasteful and packed with nutrients that contain flavonoids,proteins,amino acids,vitamins and other healthy substances.Soybean sprouts have been preferred as a part of daily diets and high-quality soybean sprouts are high market demand.The usage of safe and environment friendly light-emitting diode to control the light environment has become a hotspot in the field of facility cultivation to improve the growth and quality of sprouts.In this study,Soybean sprouts varieties 'DongNong 690' were tested to investigate the effects of blue light on the synthesis of flavonoids in soybean sprouts.This will provide a theoretical basis for the application of luminous environment regulation in the production of soybean sprouts.The main results are as follows:1.The effects of light quality on the growth and nutrient quality of soybean sprouts were studied under four different light conditions:dark(D),white(W),red(R)and blue(B).Light treatment significantly reduced the hypocotyl length and fresh weight of soybean sprouts apart from the edible dry weight and water content.Compared with other light quality,the complete stool dry weight value was the highest one and the contents of isoflavones,anthocyanins,soluble sugar and ascorbic acid in soybean sprouts were significantly increased by blue light.Luminous treatment can remarkably improve the content of soluble protein in soybean sprouts,but the contents of free amino acids in soybean sprouts had no significant difference between the three light treatments compared with the control.Unlike white and red light,the blue light can notably improve the nutritional quality of soybean sprouts.2.Effects of blue light continuous illumination on the growth and flavonoid content of soybean sprouts were studied in this article.Dark treatment was used as control.The results showed that compared with the dark treatment,treated with 36h of blue light continuous illumination,the content of Kaempferol and Daidzein in the cotyledon,and the expressions of related genes CRY1,CRY2 and IFS were significantly up-regulated.As the illumination time goes on,the Daidzein content in hypocotyls was increased gradually.With the increasing of illumination time,the content of Daidzein,Genistein,Genistin and Kaempferol were first increased and then decreased in the hypocotyls,which was remarkably higher than those in the dark.Continuous blue light treatment for 6 h and 24 h significantly stimulated the activities of phenylalanine ammonia lyase(PAL)and chalcone isomerase(CHI),respectively.Moreover,continuous blue light treatment first up-regulated the expression of flavonoid biosynthesis-related structural genes(PAL,CHS,ANS,IFS)then declined,while raised the expression of blue light receptor genes(CRY1,CRY2)gradually.3.The soybean sprouts were grown in dark(D),white(W),blue light(B),blue light(B)+ 6 mM CaCl2,blue light(B)+ 0.4 mM EGTA,blue light(B)+ 6 mM CaCl2+ 0.4 mM EGTA to figure out the synthesis mechanism of flavonoids in soybean sprouts by blue light treatment.The results showed that the treatment of blue light(B)and Ca2+ significantly increased the content of flavonoids in the hypocotyls of soybean sprouts,and the opposite results happened in exogenous addition of EGTA.The blue light receptor genes CRY1,CRY2,PHOT1,PHOT2,flavonoid synthesis genes and HY5 were great up-regulation in the coprocessing of blue light(B)and Ca2+.After the addition of EGTA chelate Ca2+,the expression of blue light receptor genes,HY5 and flavonoid synthesis genes were notably repressed.