Effects Of Red And Blue Light Ratio On The Quality Of Eggplant Seedlings

Eggplant(Solanum melongena L.)cultivation area expands year by year in our country,and it is one of the most important vegetables for sale in domestic and export markets.With the increasing development of optical biology research and artificial light,the studies on effects of light qualities on protected vegetable crop production were more and more.Based on the early study that the R/B=1/1 treatment benefits the formation of healthy seedlings,in this paper,compared to LED white light(W)as the control,effects of the different LED red and blue light ratio[including LED blue light(B),R/B =1/1,R/B =3/1,R/B =6/1,R/B =9/1 and LED red light(R)]on root development,leaf structure,photosynthesis,carbon and nitrogen metabolism of eggplant seedlings were studied,using 'Jing Qie Jin Gang' as material.This study focused on selecting the best suitable red and blue light ratio to benefit the growth and development of eggplant seedlings,and providing theoretical support for the heathy seedlings cultivation and the development of light quality environmental regulation for the protected cultivation.The results showed that:1.The seedling index,plant dry weight,root vigor,root total absorption area and active absorption area,root structure parameters of eggplant seedlings were significantly higher than other treatments under the R/B=3/1 treatment.Under B treatment,plant height and ratio of root and shoot were higher than other treatments.The stem diameter,leaf area,plant dry weight,ratio of root and shoot,seedling index,root vigor,root total absorption area and active absorption area,root structure parameters were significantly lower than other treatments,under R light.Stem diameter was highest under R/B?1/1,total dry weight,root vigor,root total absorption area and active absorption area were followed by R/B=3/1.Under the treatments of R/B =1/1,3/1,6/1,the leaf thickness,palisade tissue,spongy tissue and lower epidermis thickness were better than other treatment.The spongy tissue of R/B=9/1 treatment was loose.The leaf structure tightness was promoted by B light.2.Under short time(0-8 h)treatment,the expression of psbB was significantly increased under different LED red and blue light ratio.The expression of rbcS,rbcL,phyA,phyB,psbA,psbB and CRY2 were significantly increased under R/B =9/1.The expression of rbcS and rbcL were significantly improved by W,R/B =1/1 and 9/1.The expression of phyA and phyB under R/B =9/1 and 1/1 were also increased significantly.The expression of psbA and psbB were improved by all treatments,except the W treatment.And the expression of CRY2 under R/B =1/1,3/1,6/1 and 9/1 were significantly improved.At the end of seedling,the R/B =3/1 treatment significantly improved the expression of rbcL,rbcS,phyA,phyB,psbA,psbB and CRY2.B treatment increased the expression of psbB and rbcS.R treatment promoted the expression of phyA.These results showed that both red and blue light were involved in the regulation of the gene expression of RuBPcase activity,light receptor and light reaction center.3.The contents of chlorophyll a,chlorophyll(a+b),chlorophyll a/b and carotenoid,Fv'/Fm',electron transfer rate(ETR),stomatal conductance,water use efficiency,RuBPcase activity,light saturation point,the light saturated photosynthetic rate,carboxylation efficiency,CO2 saturation point and the maximum regeneration rate of RuBP were significantly higher than other treatments under the R/B=3/1,and the apparent quantum efficiency(AQY)was lower than R/B =1/1,but higher than others.Chlorophyll b content,Fv/Fm,net photosynthetic rate,transpiration rate,AQY,light compensation point were higher than other treatments under the R/B=1/1,and the RuBPcase and CE were followed by R/B=3/1.Compared with B treatment,R treatment improved the photosynthetic pigment contents of eggplant seedling leaves.B treatment was more beneficial to the photosynthetic electron transfer of eggplant seedling leaves,and significantly increased the leaf chlorophyll fluorescence parameters Fv/Fm,PSII,Fv'/Fm',ETR,qP and qNP than the R treatment.4.The activities of sucrose phosphate synthase(SPS)and sucrose synthase(SS)in leaves of eggplant seedlings under R/B =3/1 were significantly higher than other treatments,which could promote the accumulation of total sugar,sucrose,glucose,fructose and starch in leaves.Compared with other treatments,the activities of glutamate dehydrogenase(GDH),glutamate synthase and nitrate reductase(NR)and glutamine synthetase also increased significantly under R/B =3/1,which could significantly increase the contents of ammonium nitrogen,non protein nitrogen,soluble protein and free amino acid in leaves.The SPS,GDH,NR activities and the contents of total sugar,fructose,soluble sugar and non protein nitrogen under R/B=1/1 treatment were lower than that of R/B =3/1,but the contents of reducing sugar and soluble sugar was the highest.Total nitrogen content of B treatment was the highest.There were the highest amylase activity and nitrate content under R treatment,and the highest protein nitrogen content under the R/B =6/1 treatment,but there wrer no significant difference on the SPS and SS activities,the contents of reducing sugar,glucose,nitrate nitrogen,non protein nitrogen and soluble protein between R/B =6/1 treatment and R/B =3/1 treatment.