|Cochran, Verlan - ARS RETIRED|
Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 21, 2005
Publication Date: September 19, 2005
Citation: Conn, J.S., Cochran, V. 2006. Response of potato (solanum tuberosum l.)to elevated atmospheric CO2 in the North American subarctic. Agriculture, Ecosystems and Environment 112:49-57. Interpretive Summary: Little is known about the response of crops to increasing atmospheric carbon dioxide (CO2) when they are grown under the cool temperatures and long day lengths that occur in summer at high latitudes such as Alaska. The potato cultivar Shepody was grown in chambers at normal atmospheric CO2 levels and at 1.5 and 2-times current levels. Potatoes were also grown outside of the chambers to determine what effect the chambers had on potatoes. Six plants were harvested in late July and August from each treatment and the plants were separated into various plant parts. Potato leaf appearance rate and canopy development did not differ between CO2 treatments. At the first harvest, the number of stems, total stem weight, number of flowers, and total flower dry weight decreased with increasing CO2. Weight of stems and leaves declined while weight of tubers increased with elevated CO2. Roots made up a higher proportion of plant total weight and percent leaf nitrogen declined 11% with increased CO2. At the final harvest, total tuber dry weight in the 2-times CO2 chambers was 36% higher than in the normal CO2 chambers but yields in the chambers were lower than outside the chambers due to 7 - 14% less photosynthetic active radiation in the chambers. The results show that potato yields can be expected to increase at atmospheric CO2 levels increase, even under the cool climate and long day lengths found at high latitudes. The results also showed that potato growth and yield is sensitive to changes in light levels, which could be influenced by any changes in cloudiness brought about through global climate change.
Technical Abstract: The response of potato (Solanum tuberosum L., cv. Shepody) to elevated CO2 was studied in 1994 at Fairbanks, Alaska using open-top chambers. Three CO2 exposure levels were used in the chambers: ambient (A); A + 175 uM M-1 CO2 (A+175); A + 350 uM M-1 CO2 (A+350). Plots were also established outside of the chambers (ANC) to test chamber affects. Potato leaf appearance rate and canopy development did not differ between CO2 treatments. Two biomass harvests were conducted in late July and August. Six plants in each plot were removed from the soil and separated into roots, stems, leaves, tubers and flowers. 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 that allocated to tubers increased with elevated CO2. Root:shoot ratio was larger and percent leaf nitrogen declined 11% with increased CO2. At the final harvest, total tuber dry weight in the 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 due to 7 - 14% less photosynthetic active radiation in chambers. Net photosynthesis was measured July 13 and August 5. 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.