Effets de l'augmentation du CO2 atmosphérique sur la physiologie et les paramètres de rendement du haricot

Effects of elevated CO2 on the physiology and yield parameters of bean. The effects of elevated CO2 on bean ( Phaseolus vulgaris) physiology were analysed in greenhouses at 350 mul/l and at 700 mul/l (i.e. twice the actual level). The photosynthesis of beans grown under high CO2 concentration increased (+73% until the 40th day after germination). At high concentration, leaf nitrogen content was 15% lower while the C/N ratio was 19% higher. Leaf soluble and unsoluble sugar contents increased (+49 and +64%, respectively). The CO2 doubling significantly increased leaf area by 36% and leaf mass by 57%. Two months after sowing, plants exposed to 700 mul/l produced pods with higher fresh and dry weights (+44 and +110%, respectively). The individual pod dry weight and length also were also higher (+100 and +10%) but the number of seeds per pod was reduced (-9%). The soluble sugar content increased by 41%. In summary, the results suggest that the CO2 doubling has an important effect on bean yield, particularly on the quantitative level, but the increase in the soluble sugar content was more important on the qualitative level.