Photosynthesis redux

Croplands are environmentally destructive, and already take up 12% of the earth’s liveable space. Could more efficient plants feed a hungrier world?

 
  More efficient agriculture could help us feed a booming human population.   Eric B. Walker/Flickr  (CC BY-NC 2.0)

More efficient agriculture could help us feed a booming human population. Eric B. Walker/Flickr (CC BY-NC 2.0)

 

The projections point towards hunger: By 2050, the global population will reach 9 billion people, and we will not be able to feed them all. The Food and Agriculture Organization of the United Nations estimates that an additional 2 billion mouths, and a growing appetite for meat in developing countries, will require our current agricultural yield to rise as much as 70% — an increase we are not on track to meet.

It’s unlikely that humans will be able to grow our way out of this problem, but we might be able to engineer our way out.

An innovative new method out of labs at the University of Illinois and the University of California, Berkeley suggests that genetic engineering could help close the gap by making plants up to 15% more productive. The team created this jump by improving on what is already one of the greatest success stories of the biological world: photosynthesis.

“A lot of people have questioned whether increasing photo-efficiency would do anything for productivity,” says Stephen Long, whose lab at the University of Illinois was responsible for the theoretical photosynthesis research that spurred the project.

"Crop breeders are selecting genes all the time for productivity, yet between old cultivars of a crop and modern ones, there was hardly any difference in photosynthesis efficiency. But we identified a few points where we thought, we can engineer an improvement.”

One such point: It turns out that, throughout the course of a normal day, photosynthesis does not always operate at maximum efficiency.

When a plant is exposed to very strong sunlight or a rapid increase in sunlight, it ramps down photosynthesis, releasing excess energy to protect the leaf from bleaching. However, when this sunlight is blocked — say, by clouds passing over the sun, or wind blowing leaves into a new position — the plant is slow to relax back into a normal state, causing a loss in productivity.

To address this inefficiency in tobacco plants, the team inserted extra genes that regulated the enzymes controlling this cycle. This allowed the plants to produce the enzymes in greater amounts. Led by University of Illinois researchers Johannes Kromdijk and Katarzyna Glowacka, the plants were then grown in an Illinois field, where they exhibited a much quicker relaxation time, a higher CO2 uptake, and a 14–20% higher plant mass and leaf area. All in all, this translated to a roughly 15% increase in productivity.

 
  Using genetic engineering, researchers produced tobacco plants with increased productivity.   Ikhlasul Amal/Flickr  (CC BY-NC 2.0)

Using genetic engineering, researchers produced tobacco plants with increased productivity. Ikhlasul Amal/Flickr (CC BY-NC 2.0)

 

According to Long, the modifications made to tobacco should be easy to apply to any other vascular plant, which includes every crop currently grown for human consumption. The team is currently working on applying these changes to soybean, maize, cassava, cowpea and rice.

The team, well aware of the objections to genetically modified food, also express hope that their methods will inspire less controversy than is seen around transgenic foods, as it uses genes that encode proteins found in all plants.

“If one objects to the use of genes taken from one plant and expressed in another, we could do this with the native genes from any plant species,” says Krishna Kumar, a photosynthesis researcher at the University of California, Berkeley, whose lab partnered with Long’s to perform the study. Long also notes that this increased enzyme expression could even occur naturally, through mutation.

Such extra-efficient crops could be good news for the environment: more food could be grown without converting additional forest to cropland. Croplands already make up about 12% of Earth’s liveable land, taking up an area about the size of South America, and this area is growing every year. Removing this forest is disastrous for local biodiversity. Additionally, estimates suggest that deforestation releases around one petagram carbon per year — equal to 1 billion metric tons of carbon, or the amount of CO2 released by 775 million passenger cars every year.

But does all of this mean more efficient genetic engineering is the answer to our food problem?

“If the question is whether an increase in crop productivity of 15% through biotechnology will be enough to offset the increasing demand for food in this century, the answer is no,” says Sylvie De Blois, plant science ecologist and director of McGill University’s School of Environment.

De Blois believes that addressing growing demands will require a combination of strategies that emphasise sustainability over returns — like better fertilisation and irrigation, local projects in urban areas as well as rural, and decreases in post-harvest loss and food wastage. The World Resources Project estimates about a third of the food we produce is wasted every year.

“I believe it is a variety of approaches and practices that may work, and not just one biotechnological fix,” says De Blois. “Diversifying agricultural strategies, like diversifying crops, can increase the resilience of our food system.”

 
  Feeding our growing global population, especially in developing nations, will take a combination of approaches.   ICRISAT/Flickr  (CC BY-NC 2.0)

Feeding our growing global population, especially in developing nations, will take a combination of approaches. ICRISAT/Flickr (CC BY-NC 2.0)

 

Nathan Mueller, a postdoctoral researcher at Harvard University studying the environmental challenges that arise from land use and agriculture, agrees.

“This sort of work is definitely promising, as it potentially allows for a change in crop yields of the sort that is becoming harder and harder to come by,” he says. However, he emphasises that there are many areas of the world where priority should go not to new crop varieties but to addressing existing, solvable problems — like soil moisture, pests, and nutrient supply. “Improving access to currently available agricultural technologies, and increasing capital available to farmers, will be most critical to increasing yields in those areas.”

Because the research was funded by the Bill and Melinda Gates Foundation, it might be particularly heartening to researchers like Mueller that, if this technology works in other crops, it will first be offered at a low cost to farmers in Africa, who could benefit considerably from its promise. After all, the urgency of improving yields in places that need it most is growing every year — particularly as climate change begins altering local conditions.

“These shortages in foodstuffs, they may not hit for 10 or 20 years, but it will take any innovation we have today being farmed at scale for at least 15 years to address them,” says Long. “If we don’t start putting these technologies on the shelf now, we won’t have them when society feels we need them.”

Edited by Andrew Katsis and Ellie Michaelides