Consequences of High C 0 2-Concentrations in Air on Growth and Gas-Exchange Rates in Tobacco Mutants

P. He*, K. P. Bader, A. Radunz and G.H. Schmid Lehrstuhl für Zellphysiologie, Fakultät für Biologie, Universität Bielefeld, Postfach 10 01 31, D-33501 Bielefeld, Bundesrepublik Deutschland Z. Naturforsch. 50c, 781-788 (1995); received July 3/July 30, 1995 High C 0 2-Pressure, Mass Spectrometry, Tobacco, Photosynthesis, Photorespiration Wild type tobacco N. tabacum var. John William's Broadleaf and the tobacco aurea mutant Su/su were permanently grown under 700 ppm C 0 2 in air. In comparison to plants grown under 350 ppm C 0 2 in air but under otherwise identical conditions growth was substantially enhanced. Gas exchange measurements carried out by mass spectrometry show that the rate of photosynthesis in the wild type and in the mutant is increased by more than 100%. The photorespiratory rate in the wild type measured as 180 2-uptake in the light in the “700 ppm C 0 2-plants” is not reduced to the extent expected or deduced from experiments in which the 350 ppm system responds under in vitro conditions to 700 ppm C 0 2. An analysis of the induction kinetics of room temperature fluorescence kinetics of the adapted (700 ppm C 0 2) system and the control system (350 ppm C 0 2) under various C 0 2-partial pressures shows that permanent growth under the elevated C 0 2-partial pressure leads to a structural modifi­ cation of the photosynthetic apparatus.