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Agriculture (Species: Potato) -- Summary
Nearly all agricultural crops respond to increases in the air's CO2 content by exhibiting increases in photosynthesis, biomass production and water use efficiency, as well as an enhanced ability to withstand the normally-deleterious effects of air pollution.  In this summary, we review some recent reports of these phenomena in potato plants (Solanum tuberosum L.).

In the study of Sicher and Bunce (1999), exposure to twice-ambient atmospheric CO2 concentrations enhanced rates of net photosynthesis in potato plants by 49%; while in the study of Schapendonk et al. (2000), a doubling of the air's CO2 content led to an 80% increase in net photosynthesis.  In a study that additionally considered the role of the air's vapor pressure deficit (VPD), Bunce (2003) found that exposure to twice-ambient atmospheric CO2 concentrations boosted net photosynthesis by 36% at a VPD of 0.5 kPa (moist air) but by 70% at a VPD of 3.5 kPa (dry air).  Yet another complexity was investigated by Olivo et al. (2002), who assessed the effect of a doubling of the air's CO2 content on the net photosynthetic rates of high-altitude (Solanum curtilobum) and low-altitude (S. tuberosum) and found the rate of the former to be enhanced by 56% and that of the latter by 53%.  In addition, although they did not directly report photosynthetic rates, Louche-Tessandier et al. (1999) noted that photosynthetic acclimation was reduced in CO2-enriched plants that were inoculated with a fungal symbiont, which consequently allowed them to produce greater amounts of biomass than non-inoculated control plants grown in ambient air.

Because elevated CO2 concentrations stimulate photosynthesis in potatoes, it is only to be expected they would also increase potato biomass production.  And so they do.  Miglietta et al. (1998), for example, reported that potatoes grown at 660 ppm CO2 produced 40% more tuber biomass than control plants grown in ambient air.  Such reports are common, in fact, with twice-ambient atmospheric CO2 concentrations having been reported to produce yield increases of 25% (Lawson et al., 2001), 36% (Chen and Setter, 2003), 37% (Schapendonk et al., 2000), 40% (Olivo et al., 2002), 44% (Sicher and Bunce, 1999), 85% (Olivo et al., 2002) and 100% (Ludewig et al., 1998).

A few studies have been conducted at even higher atmospheric CO2 concentrations.  Kauder et al. (2000), for example, grew plants for up to seven weeks in controlled environments receiving an extra 600 ppm CO2, obtaining final tuber yields that were 30% greater than those of ambiently-grown plants.  Also, in a study of potato microcuttings grown for four weeks in environmental chambers maintained at ambient air and air enriched with an extra 1200 ppm CO2, Pruski et al. (2002) found that the average number of nodes per stem was increased by 64%, the average stem dry weight by 92%, and the average shoot length by 131%.

Atmospheric CO2 enrichment also leads to reductions in transpirational water loss by potato plants.  Magliulo et al. (2003), for example, grew potatoes in the field within FACE rings maintained at either ambient (370 ppm) or enriched (550 ppm) atmospheric CO2 concentrations for two consecutive years, finding that the CO2-enriched plants used 12% less water than the ambient-treatment plants, while they produced 47% more tuber biomass.  Hence, the CO2-enriched plants experienced a 68% increase in water use efficiency, or the amount of biomass produced per unit of water used in producing it.  Likewise, Olivo et al. (2002) found that a doubling of the air's CO2 content increased the instantaneous water-use efficiencies of high-altitude and low-altitude potato species by 90% and 80%, respectively.

In the final phenomenon considered here, we review the findings of three studies that evaluated the ability of atmospheric CO2 enrichment to mitigate the deleterious effects of ozone pollution on potato growth.  Fangmeier and Bender (2002) determined the mean tuber yield of potato as a function of atmospheric CO2 concentration for conditions of ambient and high atmospheric O3 concentrations, as derived from a trans-European set of experiments.  At the mean ambient CO2 concentration of 380 ppm, the high O3 stress reduced mean tuber yield by approximately 9%.  At CO2 concentrations of 540 and 680 ppm, however, the high O3 stress had no significant effect on tuber yield.

Much the same results were obtained by Wolf and van Oijen (2002, 2003), who used the validated potato model LPOTCO to project future European tuber yields.  Under two climate change scenarios that incorporated the effects of increased greenhouse gasses on climate (i.e., increased air temperature and reduced precipitation), the model generated increases in irrigated tuber production ranging from 2,000 to 4,000 kg of dry matter per hectare across Europe, with significant reductions in the negative effects of O3 pollution.

In summary, it is clear that as the CO2 content of the air increases, potato plants should exhibit increases in photosynthesis, biomass production, water use efficiency and ozone pollution resistance that should significantly enhance the tuber yields of this important agricultural staple.

References
Bunce, J.A.  2003.  Effects of water vapor pressure difference on leaf gas exchange in potato and sorghum at ambient and elevated carbon dioxide under field conditions.  Field Crops Research 82: 37-47.

Chen, C.-T. and Setter, T.L.  2003.  Response of potato tuber cell division and growth to shade and elevated CO2Annals of Botany 91: 373-381.

Fangmeier, A. and Bender, J.  2002.  Air pollutant combinations - Significance for future impact assessments on vegetation.  Phyton 42: 65-71.

Kauder, F., Ludewig, F. and Heineke, D.  2000.  Ontogenetic changes of potato plants during acclimation to elevated carbon dioxide.  Journal of Experimental Botany 51: 429-437.

Lawson, T., Craigon, J., Black, C.R., Colls, J.J., Tulloch, A.-M. and Landon, G.  2001.  Effects of elevated carbon dioxide and ozone on the growth and yield of potatoes (Solanum tuberosum) grown in open-top chambers.  Environmental Pollution 111: 479-491.

Louche-Tessandier, D., Samson, G., Hernandez-Sebastia, C., Chagvardieff, P. and Desjardins, Y.  1999.  Importance of light and CO2 on the effects of endomycorrhizal colonization on growth and photosynthesis of potato plantlets (Solanum tuberosum) in an in vitro tripartite system.  New Phytologist 142: 539-550.

Ludewig, F., Sonnewald, U., Kauder, F., Heineke, D., Geiger, M., Stitt, M., Muller-Rober, B.T., Gillissen, B., Kuhn, C. and Frommer, W.B.  1998.  The role of transient starch in acclimation to elevated atmospheric CO2FEBS Letters 429: 147-151.

Magliulo, V., Bindi, M. and Rana, G.  2003.  Water use of irrigated potato (Solanum tuberosum L.) grown under free air carbon dioxide enrichment in central Italy.  Agriculture, Ecosystems and Environment 97: 65-80.

Miglietta, F., Magliulo, V., Bindi, M., Cerio, L., Vaccari, F.P., Loduca, V. and Peressotti, A.  1998.  Free Air CO2 Enrichment of potato (Solanum tuberosum L.): development, growth and yield.  Global Change Biology 4: 163-172.

Olivo, N., Martinez, C.A. and Oliva, M.A.  2002.  The photosynthetic response to elevated CO2 in high altitude potato species (Solanum curtilobum).  Photosynthetica 40: 309-313.

Pruski, K., Astatkie, T., Mirza, M. and Nowak, J.  2002.  Photoautotrophic micropropagation of Russet Burbank potato.  Plant, Cell and Environment 69: 197-200.

Schapendonk, A.H.C.M., van Oijen, M., Dijkstra, P., Pot, C.S., Jordi, W.J.R.M. and Stoopen, G.M.  2000.  Effects of elevated CO2 concentration on photosynthetic acclimation and productivity of two potato cultivars grown in open-top chambers.  Australian Journal of Plant Physiology 27: 1119-1130.

Sicher, R.C. and Bunce, J.A.  1999.  Photosynthetic enhancement and conductance to water vapor of field-grown Solanum tuberosum (L.) in response to CO2 enrichment.  Photosynthesis Research 62: 155-163.

Wolf, J. and van Oijen, M.  2002.  Modelling the dependence of European potato yields on changes in climate and CO2.  Agricultural and Forest Meteorology 112: 217-231.

Wolf, J. and van Oijen, M.  2003.  Model simulation of effects of changes in climate and atmospheric CO2 and O3 on tuber yield potential of potato (cv. Bintje) in the European Union.  Agriculture, Ecosystems and Environment 94: 141-157.