The Effects Of CO₂ Enrichment On Occurrence Of Blight Of Watermelon At Seedling Stage

This experiment used watermelon young seedling to be experiment material,studied CO₂ enrichment on the photosynthetic rate,resistant matter,protective enzyme,MDA, active oxygen and other physiological and biochemical indicators of dynamic change of watermelon seedlings during seedling stage,Analysis of mutual relations of these physiological and biochemical changes and occurrence situation of blight of watermelon seedling stage.And the effects of mycelium date growth and spore germination rate of the different CO₂ concentration on Fusarium oxsporum f.sp.niveum,The results showed:1.CO₂ enrichment significantly reduced the morbidity and disease index of blight of watermelon seedling,the feeling disease ability of HO₁,HO₂ was weaker,the effects of prevention were fairly good,the effect of prevention of 1200uL·L^-1was best,the morbidity came down 35.71%,32.56%,the disease index came down 37.74%,34.36%; That feeling disease ability of Sh was higher,the morbidity and disease index had dropped 6.52%～23.91%,5.78%～25%respectively.2.With increasing of concentration of CO₂ four fungiform mycelium date growth and spore germination rate were the corresponding change.Compared with the antitheses,the amounts of mycelial date growth cut down respectively HO₁,0.02～0.10;HO₂ 0.02～0.12;HO₃,0.01～0.08;Sh.0.01～0.25(cm).The action of inhibitor of amounts of four myceliums date growth had not been obvious under low concentrations,had been even promoted;The spore germination rate of HO₁,HO₂,HO₃,Sh were significantly inhibited compared with the ck in 1600,1800,2000,1400uL·L^-1,the spore germination rates were lower 4.3%～9.8%,2.7%～5.6%,2.0%～3.7%.2.2%～11.9%.3.CO₂ enrichment processed watermelon seedlings,the net photosynthetic rate was a significant change.Compared with the ck,under four CO₂ concentrations the increases of average Pn were 22.04%.61.02%,96.75%and 73.98%.Intercellular CO₂ concentration increased 38.49%,51.16%.57.96%and 72.94%.4.CO₂ enrichment significantly promoted watermelon seedling growth,plant height, stem diameter,leaf area,and nurtured strong seedlings.Compared with the ck,the plant height increased 26.1%～154%;stem diameter increased 27.1%～71.9%.Plant height was greater than the rate of stem diameter,leaf area increased 15.1%～45.7%.The exponent of the strong seedling was 0.1416,0.1951,0.2272,0.2678 and 0.2884 respectively5.Effect of CO₂ enrichment generally increased carbohydrate content of watermelon seedlings,The content of V_C increased 2.04%～16.16%,the content of soluble sugar increased 6.60%～41.08%.the content of organic acid increased 18.18%～97.40%.the content of soluble protein increased 12.01%～22.05%.6.CO₂ enrichment had improved the enzyme activity of SOD,POD,CAT,AsA-POD of stem leaf of watermelon young seedling,the enzyme activity of AsA-POD changed most significantly,And the contents of MDA had decreased in varying degrees,respectively 13.18%,28.45%,44.18%.47.02%.7.With increasing concentration of CO₂,the downward trend of the content of H₂O₂ and the production rate of O_2·-of watermelon seedling is different,1200uL·L^-1droped most obviously to 20.17%,36.88%respectively.