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Nonstructural Carbohydrates -- Summary
When the air's CO2 content rises, nearly all of earth's plants experience increased rates of photosynthesis; and because photosynthesis converts carbon dioxide into sugars, elevated levels of atmospheric CO2 practically always stimulate the production of nonstructural carbohydrates.  In turn, with greater nonstructural carbohydrates, CO2-enriched plants have more raw materials at their disposal for facilitating increased growth and development.  In this review, we thus highlight some of our earlier Journal Reviews that document this phenomenon.

In the study of Allen et al. (1998), the authors grew soybeans at atmospheric CO2 concentrations ranging from 160 to 900 ppm, finding that total nonstructural carbohydrate concentrations in all plant parts increased with increasing CO2.  This phenomenon has also been observed in many other agricultural crops, including alfalfa (Sgherri et al., 1998), potato (Miglietta et al., 1998), cotton (Reddy et al., 1998) and, once again, soybean (Sims et al., 1998).

Elevated CO2 has also been shown to enhance nonstructural carbohydrate concentrations in the leaves of various trees.  Wurth et al. (1998), for example, observed 30 to 100% CO2-induced increases in sugar and starch concentrations within leaves of four semi-deciduous tropical forest species in response to a doubling of the atmospheric CO2 content.  Similar CO2-induced increases in leaf nonstructural carbohydrate concentrations have been reported in spruce (Roberntz and Stockfors, 1998), oak (Tognetti et al., 1998) and a leguminous species native to Australia (Schortemeyer et al. 1999).

In conclusion, the scientific literature clearly demonstrates that as the air's CO2 content continues to rise, earth's plants will almost certainly respond by increasing their nonstructural carbohydrate supply, which can then be used to support increased plant growth and development.  As an editorial aside, we note that this phenomenon - the tendency for atmospheric CO2 enrichment to increase nonstructural carbohydrate concentrations - is so ubiquitous within the plant kingdom that we often choose not to list new Journal Reviews under this heading, as it would take too much space to store all the relevant information.

Allen, L.H., Jr., Bisbal, E.C. and Boote, K.J.  1998.  Nonstructural carbohydrates of soybean plants grown in subambient and superambient levels of CO2Photosynthesis Research 56: 143-155.

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.

Reddy, K.R., Robana, R.R., Hodges, H.F., Liu, X.J. and McKinion, J.M.  1998.  Interactions of CO2 enrichment and temperature on cotton growth and leaf characteristics.  Environmental and Experimental Botany 39: 117-129.

Roberntz, P. and Stockfors, J.  1998.  Effects of elevated CO2 concentration and nutrition on net photosynthesis, stomatal conductance and needle respiration of field-grown Norway spruce trees.  Tree Physiology 18: 233-241.

Schortemeyer, M., Atkin, O.K., McFarlane, N. and Evans, J.R.  1999.  The impact of elevated atmospheric CO2 and nitrate supply on growth, biomass allocation, nitrogen partitioning and N2 fixation of Acacia melanoxylonAustralian Journal of Plant Physiology 26: 737-774.

Sgherri, C.L.M., Quartacci, M.F., Menconi, M., Raschi, A. and Navari-Izzo, F.  1998.  Interactions between drought and elevated CO2 on alfalfa plants.  Journal of Plant Physiology 152: 118-124.

Sims, D.A., Luo, Y. and Seeman, J.R.  1998.  Comparison of photosynthetic acclimation to elevated CO2 and limited nitrogen supply in soybean.  Plant, Cell and Environment 21: 945-952.

Tognetti, R., Johnson, J.D., Michelozzi, M. and Raschi, A.  1998.  Response of foliar metabolism in mature trees of Quercus pubescens and Quercus ilex to long-term elevated CO2Environmental and Experimental Botany 39: 233-245.

Wurth, M.K.R., Winter, K. and Korner, C.  1998.  Leaf carbohydrate responses to CO2 enrichment at the top of a tropical forest.  Oecologia 116: 18-25.