修 広田

作物の群落構造と物質生産 : 受光およびCO_2拡散 : V.グレインソルガムの草高が群落光合成に及ぼす影響

The field experiment was carried out to study the effect of canopy height on CO_2 diffusion and canopy photosynthesis using the isogenic line of grain sorghum with different canopy height. Using the data obtained from the field experiment, CO_2 profile and canopy photosynthesis of grain sorghum were simulated. The results of the study are summarized as following; Canopy architecture of tall type grain sorghum was superior to the short type in all the factors concerning the CO_2 diffusion (wind speed at canopy surface, drag coefficient, attenuation coefficient of wind speed, mixing length and leaf width). High leaf photosynthetic rates (more than 100 mg CO_2/dm^2h) were observed under a field condition. The CO_2 profiles simulated by using these values of leaf photosynthesis coincided with CO_2 profiles measured in the canopy. Crop photosynthesis of tall type grain sorghum which has a LAI of 6.27 was 12% higher than that of short type which has a LAI of 5.21. Under the condition of a LAI of 6.0, the crop photosynthesis of tall type was 8% higher than short type canopy.