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Feeding the World Four Decades from Now

Rosenthal, D.M., Locke, A.M., Khozaei, M., Raines, C.A., Long, S.P. and Ort, D.R. 2011. Over-expressing the C3 photosynthesis cycle enzyme Sedoheptulose-1-7 Bisphosphatase improves photosynthetic carbon gain and yield under fully open air CO2 fumigation (FACE). BMC Plant Biology 11: 123.
According to Rosenthal et al. (2011), "at current levels of crop productivity, global food requirements may outpace current crop production by the middle of this century," citing the studies of Bruinsma (2003), Lobell et al. (2009) and Long and Ort (2010); and they say that "direct improvements in photosynthetic efficiency will be needed if we are to meet global food needs in the future." In this regard, therefore, and based on the work of Lefebvre et al. (2005), Ainsworth and Ort (2010) and Yamori et al. (2010), they hypothesize that if crops could be engineered with an increased capacity for the regeneration of RuBP (Ribulose-1,5-bisphosphate, an organic substance that is involved in photosynthesis), such plants "would have a greater increase in productivity in elevated CO2 when compared to wild type plants," and they feel that this boost in productivity could provide the extra food that will be needed four decades from now to feed the world's burgeoning human population. Hence, they decided to explore this concept experimentally.

Wild type tobacco (Nicotiana tabacum) and "transformed" tobacco that overexpresses the C3 cycle enzyme sedoheptulose-1,7 bisphosphatase (SBPase) were grown in the field at the Soy-FACE facility of the University of Illinois at Urbana-Champaign under ambient (385 ppm) and enriched (585 ppm) atmospheric CO2 concentrations, during which time a number of plant properties and processes were assessed, in order to determine the ultimate impact of the aerial fertilization effect of atmospheric CO2 enrichment on the two types of plants.

The six scientists determined that growth under elevated CO2 stimulated instantaneous net photosynthesis, as well as the diurnal integral of net photosynthesis, more in the transformed plants than in the wild type plants; and although there was some evidence of photosynthetic acclimation in both sets of plants, there was still a greater CO2-induced stimulation of final biomass in the transformed plants than in the wild-type plants (22% vs. 13%).

Noting that their study "demonstrated that transgenic tobacco plants with increased SBPase have the potential for greater stimulation of photosynthesis and biomass production relative to wild type tobacco when grown at elevated CO2," Rosenthal et al. say their results "provide proof of concept that increasing [the] content and activity of a single photosynthesis enzyme can enhance carbon assimilation and yield of C3 crops grown at CO2 concentrations expected by the middle of the 21st century," which productivity boost they feel will be needed in order to adequately feed the world's projected population at that point in time.

Additional References
Ainsworth, E.A. and Ort, D.R. 2010. How do we improve crop production in a warming world? Plant Physiology 154: 526-530.

Bruinsma, J. (Ed.). 2003. World Agriculture: Towards 2015/2030. Earthscan, London, United Kingdom.

Lefebvre, S., Lawson, T., Zakhleniuk, O.V., Lloyd, J.C. and Raines, C.A. 2005. Increased sedoheptulose-1,7-bisphosphatase activity in transgenic tobacco plants development. Plant Physiology 138: 1174.

Lobell, D.B., Cassman, K.G. and Field, C.B. 2009. Crop yield gaps: Their importance, magnitudes, and causes. Annual Review of Environment and Resources 34: 179-204.

Long, S.P. and Ort, D.R. 2010. More than taking the heat: crops and global change. Current Opinion in Plant Biology 13: 241-248.

Yamori, W., Takahashi, S., Makino, A., Price, G.D., Badger, M.R. and von Caemmerer, S. 2010. The roles of ATP synthase and the cytochrome b(6)/f complexes in limiting chloroplast electron transport and determining photosynthetic capacity. Plant Physiology 155: 956-962.

Archived 3 January 2012