PARENT SESSION
Posters P1D Photosynthesis and global change. Abstracts (699-710)

Studies of photosynthesis and biomass by growth analysis and continuous monitoring of gas exchange. Hideaki Usuda^*,1, ¹ Teikyo University, Medical School, Lab of Chem., Hachioji, Japan

ABSTRACT- 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 simultaneous measurements of continuous monitoring of CO₂ exchange and growth analysis (RGR, NAR, LAR, LWR, & SLA) with whole plants to evaluate the impact of elevated CO₂ on whole plant photosynthesis and biomass. A radish cultivar with a big storage root was grown under 4 different conditions (1: ambient CO₂ of ca. 380 ppm and 23 molE/m²/day, 2: elevated CO₂ of ca. 750 ppm and 23 molE/m²/day, 3: ambient CO₂ of ca. 380 ppm and 15 molE/m²/day, 4:elevated CO₂ of ca. 750 ppm and 15 molE/m²/day). A radish cultivar without a big storage root was grown under two conditions of 1 & 2 mentioned above. Growth analysis and continuous measurement of CO₂ exchange were done from 15 days to 21 days after sowing. Elevated CO₂ increased biomass by 27 to 83%, leaf area by 0 to 43% and the rate of CO₂ fixation per leaf area by 1 to 28%. Increase of dry matter by elevated CO₂ is due to higher photosynthesis/leaf area and bigger leaf area, although with a cultivar having a big storage root, leaf area grown under the condition 2, stayed similar to that grown under the condition 1. These results indicate that higher rate of photosynthesis with increased leaf area does have positive effect on plant biomass of vegetative crops.

KEY WORDS: Biomass, Continuous CO₂ exchang measurements, Elevated CO₂, Growth analysis