Effect Of Rhizosphere CO₂ Concentration On Growth And Development And Related Physiological Factors Of Netted Muskmelon

High CO₂ concentration with low O₂ concentration in the soil and substrate always affect the growth and development of plants.Because of the large need of O₂ in the root of muskmelon,how does high CO₂ concentration affect its growth and development still lacks of systemic report.This study probed the effect of rhizosphere CO₂ concentration on growth and develop process,photosynthesis and root metabolism of muskmelon by employing method of aeroponic and supply CO₂ to the roots.The aim is to construct the proper cultivation method to improve rhizosphere CO₂ concentration.The main results showed as follows:1 We revealed that when CO₂ concentration above 2500μL·L^-1,growth and development of muskmelon would be restricted through the aerated treatment during anthesis and fruit time.When CO₂ concentration reached 5000μL·L^-1,the restrain effect was more serious.At the same time,the dry matter of organs would be reduced,so as the fruit qulity and yield.2 The experiment revealed that Pn,Gs,Ci and Tr would be decreased with increased rhizosphere CO₂ concentration.The results showed that elevate rhizosphere CO₂ concentration would affect the photosynthesis of muskmelon.3 The experiment revealed that root activity would increase and then decrease with high CO₂ concentration treatment for a long time.At the end of experiment,the root activity value of 2500μL·L^-1 treatment and 5000μL·L^-1 treatment were lower compared with 350μL·L^-1 treatment.The absorption and transport of nutrition were restricted in the high rhizosphere CO₂ concentration treatments,so the content of nutrition transported to the over ground was reduced.4 The experiment showed that xylem sap volume,EC value and pH value were all decreased at high CO₂ concentration.The pH was netutral when the CO₂ concentration was 350μL·L^-1,but at high rhizosphere CO₂ concentration,the pH was acidic.5 At high rhizosphere CO₂ concentration,hormone syenthesis was effected. Promote hormone IAA,GA₃ and ZT synthesis were reduced and inhibited hormone ABA synthesisi was increased.The balance of hormone was disturbed and the ratio of promote hormone and inhibited hormone was decreased.6 The experiment revealed that the amino acid synthesis was restricted when rhizosphere CO₂ concentration was high.In the detected amino acid,the separated amino acid content was reduced with elevated rhizosphere CO₂ concentration except Val and His.The total amino acid content was 350μL·L^-1＞2500μL·L^-1＞5000μL·L^-1 treatment.