The Preliminary Study On Photosynthetic Characteristics And Transcriptome Of Pepper Response To CO₂ Enrichment

Due to the frequent human activities,the photosynthesis of plants is affected by the change of CO₂ concentration in the atmosphere,the carbon supply capacity of plants is changed by CO₂ enrichment and the photosynthetic capacity of plants is also changed,which promotes the accumulation of photosynthetic compounds and biomass of plants.As one of the important vegetable crops,pepper is widely grown in the northern and Southern provinces of China.Pepper has very high economic benefits and is one of the vegetables with high output value,which is loved by the majority of growers.In this experiment,the effects of CO₂ enrichment on photosynthetic characteristics of five pepper varieties were studied.Meanwhile,in order to reveal the molecular response mechanism of pepper leaves under the CO₂ enrichment,the expression profiles of the pepper leaves under CO₂ enrichment and the control conditions were analyzed by RNA-seq technology.The results provided theoretical basis to high-quality and efficient production for facility pepper.The results were as follows:The net photosynthetic rate,stomatal conductance,transpiration rate,intercellular CO₂ concentration and other photosynthetic characteristics of five pepper varieties under CO₂ enrichment and the control conditions were measured by LI-6400.The results showed that the net photosynthetic rate of the four pepper varieties increased significantly after CO₂ enriched,except for ’Huang chao’,and the net photosynthetic rate of ’Mei da 108’ was increased most significantly,increased by 85.67%.The stomatal conductance of ’Huang chao’ and ’Huang ma’ decreased,while that of the other three pepper varieties increased.After CO₂ enrichment,the intercellular CO₂ concentration of the five pepper varieties increased significantly,and the intercellular CO₂ concentration of ’Mei da 108’ was increased most significantly,increased by 126.76%.After the enrichment of CO₂,the transpiration rate of the four pepper varieties increased,except for ’Huang chao’,the transpiration rate of ’Shou long 1 hao’ significantly increased,increased by 86.61%.Meanwhile,the light response curve and the CO₂ response curve of pepper under CO₂ enrichment and the control conditions were fitted by the curve model.The results showed that the light response curve and CO₂ response curve of different pepper varieties almost have the same change trend.With light intensity and CO₂ concentration were increased respectively,the net photosynthetic rate of five pepper varieties was increased at different degrees In addition,the light saturation point and CO₂ saturation point of both zhi jiao ’Hai feng chang jian’ and yangjiao ’huang chao’ were increased at different degrees,the light saturation point and CO₂ saturation point of cai jiao ’huang ma’ and luosi jiao ’Mei da 108’ were decreased at different degrees,and the CO₂ compensation point of all pepper varieties were increased at different degrees.‘Huang ma’ was selected as the experimental material,using RNA sequencing（RNA-Seq）and the pepper genome as a reference,the expression profile of pepper leaves grown under natural environmental conditions was compared to that of pepper leaves in an environment enriched with CO₂ and the genes associated with photosynthesis were screened.The 149 differentially expressed genes（DEGs）were identified,which were analyzed by GO functional annotation and KEGG pathway enrichment.Ten of the DEGs identified were suggested to be involved in photosynthesis and related processes;they were predicted to have roles in sugar metabolism,antioxidant function,chlorophyll and ABA biosynthesis,which affected the photosynthesis of pepper.These results lay the foundations for further investigation of the molecular mechanisms of the CO₂ enrichment reaction of Capsicum.