Photosynthesis evolved some 3 to 3.5 billion years ago, allowing organisms to turn solar energy into sugars. This process has worked pretty well for all that time, but humans have very specific requirements for the plants we grow as crops. It may be possible to tweak photosynthesis to improve yields and feed more people, according to a new study from researchers at University of California Berkeley and the University of Illinois.
Humans and other non-photosynthetic organisms need to consume food to power their metabolism, but plants make their own food with water, carbon dioxide, and sunlight. Ample sunlight is good…except when there’s too much of it, which can cause damage to the plant’s cells. Plants have a built-in mechanism called non photochemical quenching (NPQ) that diverts photons of light from their chloroplasts, radiating them as heat. This system kicks in when plants are exposed to intense light, but it takes a long time for photosynthetic sensitivity to return to normal when the plant is in the shade again.
This lag time isn’t an issue for plants in the wild, since they’re typically not clustered close together with other plants like they would be in agriculture. As the sun moves across the sky, changes in light can leave many leaves in the shade with a depressed rate of photosynthesis. It is estimated that crops plants are losing 20% productivity to NPQ. Scientists wondered if it might be possible to increase the rate at which photosynthesis returns to normal in the shade, and if doing so would improve crop yields.
To test this, the team used tobacco plants, which are commonly used in agricultural experiments thanks to their well-understood genome. Three genes from a mustard-family plant called Arabidopsis were inserted into the tobacco plant DNA. The added genes were supposed to increase the activity of three proteins involved in NPQ and boosted the recovery rate for photosynthesis in the shade. The experimental plants were monitored for carbon dioxide usage to track the rate of photosynthesis, and the total dry biomass was calculated at the end of the experiment. One of the modified tobacco lines was 14% more productive than the control, and two others were 20% more productive.
The mechanisms in this study are common to most plants, so the same techniques could work in plenty of crops. It may even be possible to up-regulate the necessary proteins without splicing in genes from other plant species. Any yield increase of this scale would be a boon to mankind; we could feed more people on less acreage. With an ever-growing population, this is the sort of research that’s desperately needed.