Studies On Non-structural Carbohydrate Accumulation And Metabolism Between Source And Sink Of Tomato Plant In Greenhouse Under The CO₂ Enrichment

To investigate the non-structural carbohydrate?NSC?accumulation and metabolism between source and sink of tomato plants under the CO₂ enrichment,contents of NSC and activities of related metabolic enzymes in different parts of toamto?"Xinghai No.12"?under different CO₂ concentrations was examined,in order to provide a theoretical reference for the scientific application of CO₂ in greenhouse,meanwhile,laying physiological foundations for revealing the response mechanism of tomato sugar metabolism to CO₂ concentration.The CO₂ concentration in greenhouse was maintained at four levels:CK(400 ?mol.mol^-1),T1(600 ?mol.mol^-1),T2(800?mol.mol^-1)and T3(1000 ?mol.mol^-1)during the whole growth period of tomato.Taking samples at the four stages of growth and development:early growth stage of fruit,rapid expansion period,green ripening stage and ripening stage.The contents of NSC?glucose,fructose,sucrose and starch?in leaf blades/middle leaf veins/leaf stalk/rachis/stem/fruit spur/peduncle/pedicel/sepal and fruit,and activities of related metabolic enzymes?sucrose synthase,sucrose phosphate synthase,invertase and amylase?in leaf blades/stem and fruit was separately measured.The main results are as follows:1 After treatment of different CO₂ concentrations,the content of soluble sugar in the "source"leaves increased significantly;excepting the starch content in the rapid expansion period of fruit was not significantly increased,the others were significantly higher than that of the control.The sucrose content in leaves was significantly higher than that of the control under the 1000?mol/mol treatment,indicating that higher CO₂ concentration promoted the accumulation of sucrose in leaves.The starch content in leaves under the 800 ?mol.mol-l treatmentl was lower than that of the other two enrichment treatments,which was beneficial to the photosynthesis and transportation of photosynthate.2 The analysis of the content of NSC in the vascular related organs under different CO₂ concentrations found that the total soluble sugar increased significantly after CO₂ enrichment,and the content of starch increased significantly under 800 ?mol.mol^-1 and 1000 ?mol.mol^-1 treatment,and it was positively correlated with the increasing CO₂ concentration.Under different CO₂ concentrations,the difference of sucrose content in various vascular organs was mainly manifested in stem and terminal vascular organs,indicating that the increase of CO₂ concentration could promote the transportion of sucrose to library.3 After CO₂ enrichment treatment,the total soluble sugar and starch content in the sepals increased in different degrees,but it increased significantly compared with the control in the fruit,and the starch content was significantly lower than the control.It indicated that the CO₂ enrichment could promote the conversion of starch to soluble sugar.The content of reducing sugar was the highest in mature fruit at 800 ?mol.mol^-1,which was related to the photosynthetic efficiency and the transport efficiency of Photosynthate at source.4 CO₂ enrichment could enhance the activities of sucrose-metabolizing enzymes and amylase,and promote the process of various glucose metabolism activity.However,enzyme activities changes of different parts in various periods had different responses to different CO₂ concentrations.In the early stage of tomato growth,the activities of sucrose synthase and sucrose phosphate synthase in the leaves,stems and fruits was higher,with the most significant under the treatment of 1000 ?mol.mol^-11;.In the later stage,the activity changes of enzymes?invertase and amylase?in various parts of the plant were significantly changed,especially in the fruits of ripening stage,which resulted in a large accumulation of hexoses,which was the most significant under the treatment of 800 ?mol.mol^-1.In summary,CO₂ enrichment can promote the accumulation of non-structural carbohydrates in the different parts of the source and library,promote the transport of sucrose to the end of the library,and promote the conversion of starch to soluble sugar and the accumulation of sugar in the process of fruit ripening.CO₂ enrichment can enhance the activities of sucrose metabolism related enzymes and amylase,and promote the activities of various carbohydrate metabolism.The CO₂ fertilizer concentration in production can be referred to 800 ?mol.mol^-1.