Response And Mechanism Of Photosynthesis To Different Light Quality In Sweet Pepper Seedlings

Light quality is an important component of light environment,which affects the growth and development of plants.In recent years,research on the relationship between light quality and growth,development,yield and quality of crop has become an important topic of concern at home and abroad.Sweet pepper?Capsicum annuum L.?is one of the main vegetables in protected cultivation in China,but the mechanism of growth and photosynthesis affected by different light quality is rarely reported.Therefore,the effects of white light?W?,red light?R?,blue light?B?,red-blue combined light?RB?1:1,RB3:1,RB6:1,RB9:1 and RB1:3 on the growth of sweet pepper seedlings were investigated,and the effects of CK?white light?,R,B and RB on photosynthesis of sweet pepper seedlings and its mechanism were further discussed,in order to provide a basis for the regulation of light environment in the protected cultivation.The results were as follows:1.Under different light quality?W,R,B,RB1:1,RB3:1,RB6:1,RB9:1 and RB1:3?,compared with white light,the Strong seedling index,stem diameter,dry weight of whole plant,root activity,root architecture parameters and chlorophyll b content of sweet pepper seedlings treated with RB3:1 were the highest,the quality of seedlings was the best.The strong seedling index,root activity,root architecture parameters and chlorophyll content of Sweet Pepper Seedlings treated with R were the lowest.2.Compared with four light qualities?CK,R,B and RB?,the net photosynthetic rate,stomatal conductance,transpiration rate,light saturation point,light saturation photosynthetic rate,carboxylation efficiency,CO₂ saturation point and RuBP maximum regeneration rate of sweet pepper seedlings treated with RB were the highest,followed by B treatment,and R treatment was lowest.Intercellular CO₂ concentration,stomatal limit value and T_RO/RC,D_IO/RC,J point and I point of OJIP curve of seedlings treated with R were the highest.The Fv/Fm,Fv'/Fm',Sm,PI_ABS,P_Itotal,?Ro and?RO of seedlings treated with B and RB were significantly higher than those of CK,while those treated with R were the lowest.3.Under four light qualities?CK,R,B and RB?,the stomatal size,stomatal density,stomatal opening ratio,leaf thickness,palisade tissue and sponge tissue thickness of sweet pepper seedlings treated with RB were significantly higher than those of other treatments.Compared with CK,B and RB treatment significantly increased the activity of Rubisco,FBPase,FBA,TK and the relative expression of FBPase,FBA,GAPDH,TK genes in sweet pepper seedlings,and R treatment was significantly lower than CK.4.According to GO enrichment analysis,compared with CK,the number of differentially expressed genes treated with R,B and RB were 2853,5426 and 936 respectively,these were divided into 53 functional groups of three groups.The main functional groups of cell component classification included membrane and organelle etc..The main functional groups of biological process classification comprised metabolic process,cellular process,signaling,multicellular organismal process,response to stimulus and biological regulation etc..The main functional groups of molecular functional classification were catalytic activity and binding etc..5.KEGG analysis showed that 6752 genes were involved in 58 KEGG pathways.Compared with CK,the number of differentially expressed genes in sweet pepper seedlings treated with R,B and RB were 58,122 and 30,respectively.Fluorescence quantitative PCR was performed on seven differentially expressed genes in the photosynthetic-related pathway,the transcriptome results were consistent with the fluorescence quantitative analysis results.The relative expression of seven differentially expressed genes in B and RB treatment were significantly higher than that in CK.