Effect Of Long-Time CO₂ Enrichment On The Growth Of Pepper In Greenhouse During Fruiting And Its Physiological Basis

Fertilization technique of carbon dioxide was a important control technique in protected environment which could enhance yield and improve quality of vegetable.But fertilization technique of carbon dioxide was lack of accurate and quantization regulation index at present.And there were little study about the effect of long-time CO₂ enrichment on the growth,development,changes rule of photosynthesis and physiological mechanism.So potential of fertilization technique of carbon dioxide was not realized.Pepper were tested as the experimental materials to study the effect of long-time CO₂enrichment on growth and development,photosynthetic physiology,leaf ultrastructure,antioxidant system and osmoregulation substance,yield and quality of pepper of autumn-winter cultivation and early-spring cultivation in greenhouse.This paper was aimed to clarify physiological mechanism,so that provide technical guidance and theoretical basis.The results were as follows:（1）A set of auxiliary device of CO₂ enrichment fertilization were invented.Combined application auxiliary device of CO₂ enrichment fertilization with liquefied carbon dioxide in cylinder could improve security,controllability,fertilization time.The auxiliary device could realize uniform fertilization,and had practical application value.（2）Long-time CO₂ enrichment promoted vegetative growth of pepper.CO₂enrichment of 1200±50μl·L^-11 promoted the growth of height and stem diameter of pepper.Promotion effect on the growth of pepper showed:earlier period of pepper growth exceeded the later stage.And CO₂ enrichment of 1200±50μl·L^-11 promoted root growth of pepper,root total length,root surface area,root total volume,root average diameter,root drought weight,root fresh weight of pepper were higher than CK.Fruit set percentage of CO₂ enrichment of 1200±50μl·L^-11 was significantly greater than CK.（3）Long-time CO₂ enrichment promoted Pn of pepper.Pepper photosynthesis under CO₂ enrichment 1200±50μl·L^-1 respectively increases by 16.1%and 36.6%in autumn-winter cultivation and early-spring cultivation.Pn of pepper in different cropping showed first increase and then decrease.Photosynthetic adaptation appeared after CO₂enrichment for 30 days and 40 days during autumn-winter cultivation and early-spring cultivation.（4）Long-time CO₂ enrichment promoted enzyme activity of Rubisco and RCA.In two cropping experiments,Pn showed a positive correlation with Rubisco and RCA,Rubisco showed a positive correlation with RCA,it explained that Rubisco and RCA played an important role in regulating Photosynthesis under long-time CO₂ enrichment.With the extension of the growth process,Rubisco and RCA enzyme activity of different treatments showed first increase and then decrease in autumn-winter cultivation and early-spring cultivation,it showed that CO₂ enrichment promoted enzyme activation effect of RCA on Rubisco,so Pn of pepper increased.In late the promotion of CO₂enrichment on RCA reduced,and the activation effect of RCA on Rubisco reduced,it caused photosynthetic adaptation.（5）The treatment of long-time CO₂ enrichment promoted stomatal closure of pepper.Therefore Gs and Trm reduced.Starch grain in chloroplast of pepper had evident increase after long-time CO₂ enrichment.More starch grain caused congestion of chloroplast space.Some grana lamella and stroma lamellae were decomposed under congestion of starch grain.It weakens photosynthesis after long-time CO₂ enrichment.（6）Long-time CO₂ enrichment improved antioxidant capacity.CO₂ enrichment of1200±50μl·L^-1 improved SOD,POD,CAT and total antioxidant capacity.And osmoregulation substance content which included soluble sugar,soluble protein and proline increased after CO₂ enrichment.MDA content and conductivity was higher than CK under long-time CO₂ enrichment.（7）Long-time CO₂ enrichment was conducive to improving of appearance quality and nutrition quality.Fruit quality such as fruit length,single fruit weight,soluble sugar,soluble protein,vitamin C and crude fiber,was improved under CO₂ enrichment of1200±50μl·L^-1 in autumn-winter cultivation and early-spring cultivation.（8）Long-time CO₂ enrich increased yield of pepper.The economic yield of CO₂enrichment of 1200±50μl·L^-1 was higher than control by 7.0%and 13.0%in two cropping experiments.The bio-yield of CO₂ enrichment of 1200±50μl·L^-1 was higher than control by 13.6%and 15.2%in two cropping experiments.