Tinkering with plants to boost crop yields

Modifying plants so they take more carbon dioxide from the atmosphere holds out hope of increasing crop yields and combating climate change.

Plant scientists in the US have devised a new way to enhance the efficiency of crops: tune up the biochemical machinery of plants such as wheat, rice, maize, or even cabbages, to make the best of the available light and so increase yields.

A second group of scientists believe they may even have gone one better than the vegetable world: they have explored plant chemistry and improved on it in order to get plants to trap more atmospheric carbon dioxide and turn it into tissue.

The first group have tested their genetic modifications only in Nicotiana, or tobacco plant – a standard experimental plant – but, in theory, what they have done could be applied to all the food staples.

And the second group has yet to test its “carbon-fixing” improvements in any living organism. But both advances could be important in combating climate change, and in delivering more food for an increasingly demanding population.

Sunlight and shade

US researchers report in the journal Science that they started, not from the photosynthesis process, but from the mechanism exploited by plants to shield themselves from too much sunlight: this alters the leaf to dissipate the excess radiation as heat. The technical term is non-photochemical quenching: NPQ.

“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 the NPQ process to relax. In the shade, the lack of light limits photosynthesis, and NPQ is also wasting light as heat,” said Stephen Long, a professor of plant biology and crop sciences at the University of Illinois at Urbana-Champaign.

Computer calculations showed that the process reduced crop productivity by 7.5 per cent to 30 per cent per day, depending on the plant, and also the temperature. So the research team introduced three genes from Arabidopsis Thaliana, or thale cress, another laboratory favourite, to boost the tobacco plant’s existing gene package for photosynthesis.

In field tests, of the three chosen modified seedling lines, two showed a 20 per cent improvement in productivity, and yields from the third were 14 per cent higher than from unmodified tobacco plants. The next step is to repeat the work in food species.

My attitude is that it is very important to have these new technologies on the shelf now, because it can take 20 years before such inventions reach farmers’ fields.

Tobias Erb, researcher, Max-Planck Institute, University of Marburg

“We don’t know for certain this approach will work in other crops, but because we’re targeting a process that is the same in all crops, we’re pretty sure it will,” says Professor Long.

Meanwhile, in the same issue of Science, researchers from Germany report that they explored the cycle of enzymes used by plants to turn carbon dioxide from the air into plant proteins and other complex compounds. They then selected 17 enzymes from nine organisms and put them together to see if they could do the same or better in the laboratory.

They ended up with a new process nearly 20 times faster than nature achieves with green leaves and sunlight. Right now, it all happens in a test tube. The researchers are thinking in the long run of new ways to provide food for livestock, or new organic products for industry, and they have plans to take the laboratory study a lot further.

Artificial photosynthesis

“These could include the introduction of synthetic CO2-fixation cycles into organisms to bolster natural photosynthesis, or, say, in combination with photovoltaics, lead the way to artificial photosynthesis; this might, at the end, jumpstart the design of self-sustaining, completely synthetic carbon metabolism in bacterial and algal systems,” said Tobias Erb of the Max-Planck Institute at the University of Marburg.

Despite political resistance and both economic and ecological concern about the introduction of genetically modified crops in Europe and many other parts of the world, basic genetic research continues in universities everywhere, because it delivers a deeper understanding of why and how organisms do what they do.

And, as the carbon dioxide ratio in the atmosphere rises in ways that drive up the global temperature, while the human population increases at around 200,000 a day, crop breeders may need all the help they can get.

“The United Nations predicts that by 2050 we’re going to need to produce about 70 per cent more food on the land we’re currently using,”  says Professor Long. “My attitude is that it is very important to have these new technologies on the shelf now, because it can take 20 years before such inventions reach farmers’ fields. If we don’t do it now, we won’t have this solution when we need it.”

This story was published with permission from Climate News Network.

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