Scientists tweak photosynthesis to increase crop yields

In attempt to allay the potential problem, scientists have hacked the process in which green plants use sunlight to convert carbon dioxide and water to glucose and oxygen

The world's population is predicted to reach 9.7 billion in 2050, but with more mouths to feed and the threat of global warming, there are fears there may not be enough food to go round.

In an attempt to relieve the potential problem, scientists have hacked the photosynthesis process in which green plants use sunlight to convert carbon dioxide and water to glucose and oxygen.

By taking advantage of deficiencies in the process they have found a new way to make plants soak up the sun more quickly, which could lead to better crop yields.

Researchers at the University of Illinois at Urbana-Champaign and the University of California, Berkeley, found they could increase the productivity of genetically-modified tobacco plants by between 14 and 20 per cent, by boosting levels of three proteins involved in photosynthesis.

While the benefits of producing extra tobacco plants may be questionable, the crop was chosen because it is easily modified.

Looking at the bigger picture, the work confirms that photosynthesis can be made more efficient to increase plant yield - a hypothesis some in the scientific community once doubted was possible.

This could revolutionise the production of food crops.

'We don't know for certain this approach will work in other crops, but because we're targeting a universal process that is the same in all crops, we're pretty sure it will,' said University of Illinois plant biology and crop sciences professor Stephen Long, who led the study.

The team targeted a process that plants use to shield themselves from excessive solar energy.

'Crop leaves exposed to full sunlight absorb more light than they can use,' Professor Long said.

'If they can't get rid of this extra energy, it will actually bleach the leaf.'

Plants protect themselves by making changes within the leaf that dissipate the excess energy as heat – a process called nonphotochemical quenching (NPQ), he explained.

'But when a cloud crosses the sun, or a leaf goes into the shade of another, it can take up to half an hour for that NPQ process to relax,' Professor Long said.

Researchers found they could increase the productivity of genetically-modified tobacco plants by between 14 and 20 per cent, by boosting levels of three proteins involved in photosynthesis

'In the shade, the lack of light limits photosynthesis, and NPQ is also wasting light as heat.'

Researchers used a supercomputer to predict how much the slow recovery from NPQ reduces crop productivity over the course of a day.

These calculations revealed 'surprisingly high losses' of 7.5 to 30 per cent, depending on the plant type and prevailing temperature.

Krishna Niyogi, an expert on the molecular processes underlying NPQ at the University of California, Berkeley, suggested boosting levels of three proteins might speed up the recovery process.

To test this concept, the team inserted a 'cassette' of the three genes - taken from the model plant Arabidopsis - into tobacco.

Professor Long said: 'The objective was simply to boost the level of three proteins already present in tobacco.'

The modified plants exhibited greater leaf area and plant height, with an overall dry weight that was 14 to 20 per cent greater than that of control plants. dailymail

The researchers grew seedlings, then tested how quickly the engineered plants responded to changes in available light.

A fluorescence imaging technique allowed the team to determine which of the transformed plants recovered more quickly upon transfer to shade.

The researchers selected the three best performers and tested them in several field plots alongside plots of the unchanged tobacco.

Two of the modified plant lines consistently showed 20 per cent higher productivity in terms of photosynthesis and carbon dioxide fixation, and the third was 14 per cent higher than the unaltered tobacco plants.

While tobacco is grown for its leaves, in food crops, it will be whatever we eat from the plant - the fruit, the seeds or the roots - that will need to increase (stock image) 

The modified plants also exhibited greater leaf area and plant height, with an overall dry weight that was 14 to 20 per cent greater than that of control plants.

Johannes Kromdijk, a postdoctoral researcher at the University of Illinois at Urbana-Champaign, said: 'Tobacco is grown for its leaves, which were substantially increased.

'But in food crops, it will be whatever we eat from the plant - the fruit, the seeds or the roots - that we will need to increase.'

Other experiments have demonstrated that increasing photosynthesis by exposing plants to high carbon dioxide results in more seeds in wheat, soy and rice, he said.

'Now we can do this genetically, and we are actively working on repeating our work in various food crops,' he said. 

 

WHAT IS PHOTOSYNTHESIS? 

The process through which plants absorb light using chlorophyll to produce chemical energy in the form of oxygen and glucose is called photosynthesis.

During the process glucose is used by the plants to breathe or is converted into starch, while oxygen is released as a waste product – giving us the air we need to breathe.

The rate of photosynthesis is altered by differing carbon dioxide levels and light intensity. If either is increased then the process will also increase, up to a limit.

Temperature also plays a part, with a higher temperature increasing the rate.

However if the temperature is too high, beyond (104°F) 40°C, the rate slows down.

Photosynthesis provides most of the energy necessary for life on Earth to exist.

But no way to artificially mimic the process has yet been created, leaving us dependent on plants to survive and thrive. dailymail

Scientists tweak photosynthesis to increase crop yields