URBANA, Ill : By 2050, the global population will have grown and urbanized so much that we will need to produce 87 percent more of the four primary
food crops – rice, wheat, soy, and maize – than we do today. The climate is projected to change over the next 30 years, with warmer temperatures and
more carbon dioxide (CO2) in the atmosphere. Crop plants can adapt to change through evolution, but at a much slower rate than the changes we are causing
in the atmosphere. Furthermore, the land available for growing crop plants is unlikely to expand to accommodate the predicted rise in demand. In fact, land suited to food crop production is being lost on a global scale.
University of Illinois crop scientist Stephen P. Long, said “We have to start increasing production now, faster than we ever have. Any innovation we make today won’t be ready to go into farmers’ fields for at least 20 years, because we’ll need time for testing, product development, and approval by government agencies. On that basis, 2050 is not so far off. That’s why we say we’re one crop breeding cycle away from starvation.”
A solution lies in genetically engineering photosynthetic mechanisms to take advantage of the projected rise in global temperatures and CO2, and to achieve much higher yields on the same amount of land, says Researchers at University of Illinois, along with their large, multi-institution team. “The rate of photosynthesis in crops like soy and rice is determined by two factors, first is the enzyme which traps the CO2, hence rubisco. Rubisco can make a mistake and use oxygen instead of CO2, under lower atmospheric CO2 levels and at high temperatures. It actually ends up releasing CO2 back into the atmosphere when it uses oxygen.”
Under higher levels of CO2, such as those projected for future climates, rubisco becomes much more efficient and photosynthesis rates naturally increase as it makes fewer mistakes. The carbon fixed by rubisco is eventually turned into carbohydrates that the plant can use as an energy source for producing grains, fruits, and vegetative structures. Rising temperatures are projected to accompany increased CO2 and unfortunately, rubisco’s increased efficiency under high CO2 begins to break down in hot climates. That’s why project partners are looking to improve rubisco so that it will operate efficiently in both high temperature and high CO2 conditions.
Long says “Our partners are looking at a wide range of rubiscos from different organisms to see whether they can find one that will make fewer of these mistakes in hot climates. The second factor that can limit photosynthesis is the rate at which everything else in the leaf regenerates the CO2-acceptor molecule, known as RuBP. As we go to higher CO2 levels, instead of being limited by rubisco, we’re limited by this regeneration step. We’re looking at ways to manipulate the speed of that regeneration.”
But the team is not stopping at improving rubisco. Now researchers developed mathematical models that showed how, by altering the way nitrogen is divided between parts of the photosynthetic apparatus, more carbohydrate could be made under conditions of higher temperature and CO2 without the crop requiring more nitrogen fertilizer.
The models were then taken for a test-run in the field. The proof of concept worked: photosynthesis rates and yield increased. The group’s next step will include tests on staple food crops in controlled environments and in field trials.
The article is published in Proceedings of the Royal Society B. Lead author Johannes Kromdijk is also at University of Illinois. The project, Realizing Increased Photosynthetic Efficiency (RIPE), is supported by the Bill and Melinda Gates Foundation.