The Physiological Effect Of CO₂ Enrichment On Muskmelon Seedlings In Plastic House

Effects of CO₂ enrichment(800μL.L^-1,1000μL.L^-1,1200μL.L^-1,1400μL.L^-1and CK) on muskmelon seedlings were studied in the experiment, such as photosynthetic characteristics,the production of dry matter,the growth indexes, the physiological indexes,yield and vigorous seedling;also CO₂ enrichment on the electrolytic leakage,antioxidant enzymes,lipid peroxidation of muskmelon seedlings in low temperature. Effects of the main environmental factors on photosynthetic characteristics of melon seedlings were also studied. Results showed as follows:1.Different concentrations of CO₂ enrichment (800μL . L^-1 ,1000μL . L^-1 ,1200μL.L^-1,1400μL.L^-1 and CK ) could obviously promote the maxim photosynthetic rates.Comparing with CK, the maxim photosynthetic rates increased by 9.59%,70.52%,80.64% and 131.21% respectively. Meanwhile, the transpiration rates descended respectively by12.16%,27.18%,37.34% and 54.65% .The difference between leaf and air temperature increased. IntercellularCO₂concentration also increased by 12.04%¹4.25%.With increasing CO₂ concentration,the light compensation point(LCP) decreased, but the light saturation point(LSP) increased.2. The chilling tolerance of CO₂-enriched plants was strengthened. Activities of POD and CAT in CO₂-enriched plants were higher obviously than those in control under cold stress, but malondiadehyde content and electrolytic leakage were lower. So CO₂ enrichment was beneficial to oxidative damage of muskmelon leaves under cold stress.3. CO₂ enrichment increased shoot height,stem diameter,leaf area and dry weight. After CO₂ enrichment for 30d, total dry weight increased by 28.46%,48.62%,83.41%and 90.09% respectively comparing with CK; Vigorous seedling index were 0.1125,0.1867,0.1909,0.2226 and 0.2385; Meanwhile ,root development was strengthened and root/shoot ratio increased.4. Yield of muskmelon increased 23.34%～88.48% after CO₂ enrichment. Also sugar content of fruit and sugar/acid ratio enhanced. Sucrose content,glucose content,fructan content in the center of fruit were all higher than in the edge of fruit.