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Abstract: The response of potato (Solanum tuberosum L., cv. Shepody) to elevated CO2 was studied in 1994 at Fairbanks, Alaska using open-top chambers (OTC). Three CO2 exposure levels were used in OTC: ambient (A); A+175μmolmol−1 CO2 (A+175); A+350μmolmol−1 CO2 (A+350). Plots were also established outside chambers (ANC) to test chamber affects. Potato leaf appearance rate and canopy development did not differ between CO2 treatments. Six plants in each plot were harvested in late July and August. At the first harvest, the number of stems, total stem weight, number of flowers, and total flower dry weight decreased with increasing CO2. Biomass allocated to stems and leaves declined while allocation to tubers increased with elevated CO2. Root:shoot ratio was larger and percent leaf nitrogen declined 12.6% with increased CO2. At the final harvest, total tuber dry weight in A+350 chambers was 36% higher than in the A treatment, but yields in open-top chamber plots were lower than the no-chamber plots possibly due to 7–14% less photosynthetic active radiation in chambers. Net photosynthesis measurements made on July 13 showed no differences due to CO2 treatment; however, on August 5, net photosynthesis of leaves grown at A+350 was 53% greater than at ambient CO2. Tuber initiation and growth began between the two photosynthesis measurements. Before tuber initiation, photosynthetic rates may have been down-regulated by insufficient carbon sink capacity. [Copyright &y& Elsevier]