Effects Of CO₂ Enrichment On Growth And Metabolism Of Roots And Rhizospheric Micro-ecosystem Of Cucumber Seedlings

The experiment studied effects of different CO₂ enrichment on growth and metabolism of roots and rhizospheric micro-ecosystem of cucumber seedling in mannul controlled environment. Three CO₂ enrichment treatments were set, 350±50μmol·mol-1CO₂ concentration(T1), 950±50μmol·mol^-1 CO₂ enrichment for 3 h every morning (T2) and 950±50μmol·mol^-1 CO₂ enrichment for 6 h every day (T3). The key results were as follow:1.Elevated CO₂ could stimulate development of cucumber roots. Elevated CO₂ could promote total root length, dry weight, branching and biomass. The effect of enrichment for 6 h every day (T3) was better than that for 3 h every morning (T2).2.Elevated CO₂ could increase root activity, root absorption area, boost NR and GS activities. The effect of CO₂ enrichment for 6 h every day was better than that of enrichment for 3 h every morning. Elevated CO₂ promoted total bleeding sap of roots. Content of ammonia, P, K, Ca, Mg, Fe, Zn, Mn and ZT increased while GA, ABA and IAA decreased.3.Most sugars, organic acids, phenolic acids and most amino acids increased significantly with elevated CO₂. The treatment, 950±50μmol·mol-1 CO₂ enrichment for 6 h every day had more obvious effects than the treatment, 950±50μmol·mol-1 CO₂ enrichment for 3 h every day. Levan, sucrose, arginine, oxalic acid, alanine, malic acid, acetic acid, lactic acid cinnamic acid,ρ- hydroxybenzoic acid and benzoic acid increased significantly. Content of sugars and phenolic acids per RFW increased but that of majority of amino acids per RFW remained unanimous or decreased and that of organic acids per RFW decreased or increased.4.Elevated CO₂ could increase number of fungi, bacterial and actinomyce in rhizospheric and non-rhizospheric soil and CO₂ enrichment had more significant influences on fungi than bacterial and actinomyce. The effects of enrichment for 6 h were better than that of enrichment every morning. Acid phosphatase, saccharase, urease and catalase activities increased slightly no...