Photosynthesis and Biomass. I. Evaluation of contribution of increased photosynthesis under elevated CO₂ to biomass by continuous monitoring of gas exchange with whole plants.

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The relationship between the rate of photosynthesis/leaf area and biomass is still not clear. Elevated CO₂ should have positive effect on C3 photosynthesis. We developed the system for monitoring CO₂ exchange with whole plants for a relatively long period to evaluate the impact of elevated CO₂ on whole plant photosynthesis and biomass. With hydroponic culture radish, cultivar of Kosena become reasonable size for harvest within 3 weeks. We monitored CO₂ exchange rate, the amount of H₂O transpired, dry and fresh weight increase, and leaf area from 2 to 3 weeks after germination under ambient (around 390 ppm) and elevated (around 750 ppm) CO₂ concentration. Elevated CO₂ accelerated growth. Plants grown under elevated CO₂ had bigger leaf area/plant. Increase of dry matter by elevated CO₂ is due to bigger leaf area and higher photosynthesis/leaf area. These results indicate that higher rate of photosynthesis does have positive effect on plant biomass.