Improving on Mother Nature

Population growth, increasing global affluence, and an expanding bio-economy are conspiring to increase emerging agricultural demand by 60 to 120% by 2050, a challenge that current rates of crop productivity improvement averaging less than two percent per year cannot meet. Meeting food demands for the growing global human population requires creatively improving crop productivity in some way; large gains may only be possible through enhancing photosynthetic efficiency.

In the years since 1960, global crop productivity increased 135% through the common use of pesticides, fertilizers and irrigation, and mechanization, along with the adoption of higher-yielding crop varieties that drove a remarkable global increase in productivity. Production has for the most part been maxed out by optimizing such factors which are not likely to generate sufficient yield increases to meet mid-century agricultural demand. However, strides in photosynthetic efficiency promise a significant growth potential of yield with the potential to even still double crop productivity.

In wheat, rice, and soybeans, photo-respiration reduces the photosynthetic conversion efficiency of light into biomass by 20 to 50 percent, with the largest losses occurring in hot dry climates where poverty rates are highest and yield increases are most sorely needed. During research, scientists tested three different pathways to improved photosynthesis, the process where plants take in carbon dioxide and uses water and the sun’s energy to create glucose and oxygen.

According to the study, some crops like rice and wheat produce toxic by-products during photosynthesis, significantly reducing efficiency. During this process, called “photorespiration,” an enzyme called Rubisco occasionally makes a “mistake” in the process of converting carbon dioxide that causes it to “grab” an oxygen molecule instead of a carbon dioxide molecule.

This is essentially anti-photosynthesis, lowering efficiency. Photosynthesis efficiency can be reduced by 20-50 percent further because of this, according to the study.

The higher the temperature plants grow in, the more this “anti-photosynthesis” occurs because the plant’s enzymes are less able to distinguish between carbon dioxide and oxygen molecules. So plants in countries like Africa and Southeast Asia suffer more from this process. In one of the tested pathways, scientists were able to create “shortcuts” in the photosynthesis pathway that allowed the unproductive by-products of photosynthesis to be recaptured, meaning less energy was lost and the plants were up to 40 percent more productive. Because plants in warmer temperatures are affected more by the “anti-photosynthesis," the affects of the engineering would likely be greater and could potentially produce even higher outcomes.

This efficiency may vary across different crops, but scientists are working to see how the process affects plants like cow pea, rice, soybean, and wheat. It could still be 12-14 years, however, before this engineering is introduced in seeds for farmers to use due to the time the “breeding cycle” takes. When introduced, the engineering would be implemented into seed gems that have already been optimized for things like RoundUp tolerance or disease resistance to further improve production of crops that have already been engineered to be more productive.

Although it is still difficult to determine the exact outputs of such engineering in terms of crop productivity, scientists’ estimate that with even a 5 percent increase in productivity, 200 million additional people could be fed. With the United Nation’s estimates for the world population increase by 2050 to be 9.8 billion, this puts the need for the production increase at 2-3 breeding cycles from now.