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Factors Affecting the Development of Flue-Cured Tobacco Grown in Artificial Environments: IV. Effects of Carbon Dioxide Depletion and Light Intensity¹

Plants grown in controlled-environment rooms are usually under a CO₂ stress that the so-called "make-up air systems" do little or nothing to alleviate. Tobacco (Nicotiana tabacum L.) rapidly depletes the CO₂ from 400 ppm (v/v) ambient level to 200 ppm. This report evaluates the effects of this CO₂ stress by comparison with plants grown in an atmosphere where CO₂ was maintained at the ambient 400 ppm level by supplemental CO₂. Light intensities of 215, 322, and 450 hlx were superimposed on both CO₂ regimes. Plant development was evaluated by physical and chemical properties of mature leaves and has been compared not only among the imposed treatment conditions, but also with the development that occurs in a natural field environment.

Several abnormalities of tobacco were noted under CO₂ stress. These include: a low concentration of reducing sugars in the cured leaves, presumably reflective of low soluble carbohydrate accumulation in mature leaves; reduced internode elongation; and epinasty of leaves during maturation. A reduced dry matter accumulation in aerial organs, concomitant with the reduced internode growth, was recorded under the CO₂ stress. Only small differences between CO₂ levels occurred for dry matter accumulation in leaf tissue.

Decreased light intensity increased accumulation of nitrogen and potassium by the plants independent of CO₂ level. Most of this increase was attributed to actively expanding tissue, in this case to growth of secondary meristems.

Key Words: Alkaloids • Reducing sugars • Leaf area • Leaf shape • Internode elongation • Nitrogen • Potassium

² Assistant Professor, Department of Soil Science, and Director of the Phytotron, North Carolina State University, Raleigh, N.C. 276O7.

Received for publication June 28, 1972.