Effects of elevated CO2 on growth and yield of different fall dormancy alfalfa

This study was conducted to determine the growth and development of three types of fall dormancy alfalfa (fall dormancy alfalfa Maverick, semi-fall dormancy alfalfa ABI700, and non-fall dormancy alfalfa UC-1465) under elevated CO2 concentration. We used an artificial climate box and open top chamber dynamic and observed seed germination, growth, and yield of three types of fall dormancy alfalfa. The results showed the following: 1) The germination rate, germination potential, germination index, and mean germination time of all three types fall dormancy alfalfa were promoted significantly when CO2 concentrations reached 550-700 μmol·mol-1. 2) Under high CO2 concentration, the growth period of the three types of alfalfa increased with CO2 concentration after 3~6 d. 3) The plant height, leaf area, fresh weight, and dry weight increased significantly under high CO2 concentration (P0.05). The fresh weight of single plant of UC-1465 was greater than Maverick and ABI700 by 19.33%~21.76% and 12.74%~13.11%, respectively, after high CO2 concentration treatment. The dry weight per plant of UC-1465 was also greater than Maverick and ABI700 by 14.85%~26.77% and 12.31%~14.58%, respectively, after high CO2 concentration treatment, while the growth advantage of the non-fall dormancy alfalfa UC-1465 was further improved. 4) CO2 concentration had no significant effect on the stem diameter except at flowering (P0.05). The stem diameters of Maverick and ABI700 during the whole growth period were larger than those of the control group under high CO2 concentration. These results suggest that the growth potential of the non-fall dormancy alfalfa and semi-fall dormancy alfalfa would be greater in the future under conditions of elevated atmospheric CO2 concentration.