The case for C4 rice
2007
Mitchell, P.L., Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK | Sheehy, J.E., Crop and Environmental Sciences Division, International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines
The case for C4 rice is summarized as a chain of argument, starting from the need to produce more rice, through higher yield potential, to the consequent improvements in growth and photosynthesis. We conclude that it is essential to make Rubisco, the key enzyme of photosynthesis, work harder, by concentrating carbon dioxide around Rubisco, thus raising the light-saturated rate of photosynthesis and greatly reducing photorespiration, as occurs in C4 photosynthesis. The additional agricultural benefits of shifting from C3 to C4 rice are that C4 photosynthesis requires (1) less Rubisco and hence less nitrogen, and (2) less water, since a steeper concentration gradient for carbon dioxide diffusion can be maintained through partly closed stomata. The chain of argument also shows that research should be planned from the perspective of what we wish to achieve, that is, from the top downward, and quantitatively as far as possible. Developments in screening phenotypes, plant breeding, molecular biology, and genetic engineering are proceeding rapidly and need to be directed toward the applied goal. The pathway to success cannot be seen completely but it is very likely that techniques will arise to enable the construction of C4 rice. The certainties of population growth, climate change, and future shortages of water for agriculture mean that it is essential to start research now.
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