Scientists testing how crops react in higher CO2 conditions than now – simulating conditions likely over the next 50 years, say that one effect will likely be that protein content will be reduced by one fifth. Plants lose the ability to absorb as much nitrogen in higher CO2 conditions. Most plants use nitrate as the most common form of nitrogen and convert it to protein.
Arnold Bloom, lead author of the UC Davis study, published in the May 14th issue of Science said that when they increased the levels of CO2 in the test to the levels scientists predict over the next 50 years, it led to “nitrogen starved” crops that contained 20% less protein for human consumption.
“Wheat grain that has been exposed to the conditions that we expect in the next few decades declines about 20 per cent,” he said.
Researchers have long known that initially, at least, higher CO2 in the atmosphere leads to improved crop productivity, but that plants eventually acclimatise to higher CO2 levels and cease to thrive as levels rise higher.
Until now, there has been no hypotheses for why this happens. Now Blooms study suggests that the inhibition of nitrate assimilation may be the reason why plants do not thrive in ever-increasing CO2-rich environments as expected.
Increasing the amount of nitrates in fertilizer did not counteract the problem. An alternative is needed, and ammonium was tested as a replacement. Those plants exposed to nitrate had difficulty in producing nitrogen-containing compounds like proteins, while those exposed to ammonium did not.
Marta Lopes, a wheat physiologist at the International Maize and Wheat Improvement Center, Mexico, warns that care would need to be taken to avoid its toxic effects on the environment.
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