Effect of Carbon Dioxide Concentration on Growth and Dry Matter Production of Crop Plants : 1. Effects on leaf area, dry matter, tillering, dry matter distribution ratio, and transpiration

[摘要] Crop plants at the 5 to 7-leaf stages possessing C3 (barley, rice, and soybean) and C4 (barnyard millet and maize) pathways of photosynthesis were cultured for 15 days in transparent growth chambers placed outdoors under 4 different carbon dioxide (CO2) concentrations from 1/2 to 10 times the normal atmosphere (ca. 350 ppm) to make clear the effects of various CO2 concentrations on growth and dry matter production. The following results were obtained: I. Increases in plant height and leaf area were promoted by high CO2 concentrations, but the degree of promotion was relatively small. At a low concentration (160 ppm), plants often elongated and had narrow drooping leaves as compared to control plants under normal CO3 concentration. 2. Increase in dry weight was promoted by high CO2 concentrations and suppressed by a low concentration. This increase proceeded up to about 3 times (sometimes 10 times) the normal concentration, and this was effected mainly through the increase in net assimilation rate. The C3- and C4-plants responded differently to CO2 concentrations, the latter giving less suppression at a low concentration and less promotion at high concentrations than the former. 3. Tillering in barley and rice was accelerated by high CO2 concentratoins and withheld by a low concentration. In rice plants, observed at the 7-leaf stage, the promotion of tillering took place at the 4th node, and the appearance of tillers was made steadier at the 2nd and 3rd nodes by high CO2 concentrations. 4. Distribution ratio of dry matter in rice and maize was in a marked contrast. In rice plant distribution to leaves was less and that to roots was increased at high CO2 concentrations, while in maize such a tendency was not observed at all. 5. Transpiration rates (dm-2 day-1) were smaller at higher CO2 concentrations. At a low concentration, the promotion of transpiration was enhanced day by day as the treatment proceeded. On fine days, the leaf temperature was about 1°C lower at a low CO2 concentration and about 1°C higher at higher concentrations as compared to control plot, but no difference was observed on cloudy days.

[学科分类] 农业科学（综合）