EFFECTS OF ELEVATED CO2 CONCENTRATION AND WARMING ON GROWTH AND YIELDOF RICE

Effects of combined treatments of CO2 (400, 660, 1200 ppm) and air tem perature (outdoor tracking, outdoor+2 degrees C) on growth and yield o f rice (Oryza sativa L. cv. Nipponbare) grown in growth chambers under natural sunlight were investigated. The effects of container size (ta nk, 3.5 l pot) on growth and yield were also examined. Plants were gro wn under simulated paddyfield conditions. Growth parameters under the elevated CO2 and temperature conditions were promoted at the maximum t iller number stage but nor at the heading stage, without appreciable d ifference in such parameters. In the 660HT plot, dry weight increased about 30% at both stages compared with the 400NT plot. In the 1200HT p lot, it increased more than that of the 660HT plot at the maximum till er number stage but at the heading stage, the degree of promotion was decreased substantially. Dry matter distribution to leaf blades was re duced, and the nitrogen ratio in leaf blades were low in plants grown in both 660HT and 1200HT plants. In the 1200HT plot, the yield was rem arkably reduced probably due to the high temperature sterility. Potted , limited-root-space plants grew smaller above-ground parts than did t ank plants (less limited), without any difference in root production. From these results, the production processes of rice crop are discusse d in terms of climate conditions predicted for the future.