Rising Atmospheric Carbon Dioxide May Reduce Protein Levels In Crops
We all learned in school that carbon dioxide (CO2) is an integral part of the photosynthesis process, in which plants assimilate nutrition by breathing in CO2 and releasing oxygen. But just as too much of something is never a good thing, a field study conducted by a UC Davis plant scientist has found that too much CO2 inhibits the ability of plants to convert nitrate to proteins, thus affecting the nutritional quality of food crops. This is a major concern, as levels of carbon dioxide have increased dramatically over the past decades due to climate change.
Like Us on Facebook
Arnold Bloom, a professor in the Department of Plant Sciences at UC Davis and lead author of the study, said in a statement that "food quality is declining under the rising levels of atmospheric carbon dioxide that we are experiencing. Several explanations for this decline have been put forward, but this is the first study to demonstrate that elevated carbon dioxide inhibits the conversion of nitrate into protein in a field-grown crop."
Plants fix nitrogen from the atmosphere, which aids in their growth by producing vital cellular products, such as proteins. These plants are eaten by humans and animals that also need amino acids and proteins for growth and metabolism. Many leguminous and non-leguminous plants, such as corn and wheat, are major sources of protein. Wheat alone provides nearly one quarter of all protein in the global human diet.
The study, a first of its kind, analyzed the effect of elevated levels of atmospheric CO2 on field-grown wheat. The experiment was conducted between 1995 and 1997, and involved releasing air with high concentrations of carbon dioxide into wheat fields at the Maricopa Agricultural Center near Phoenix, Arizona. The amount of CO2 released over the test plots was based on the projected estimates of CO2 levels in the atmosphere in the coming years. Control plantings of wheat were also grown in ambient, untreated levels of CO2.
Wheat leaf material was collected from the different test plots and, in order to preserve the nitrogen compounds over time, they were placed on ice, oven dried, and then stored in vacuum-sealed containers. Now, more than a decade later, Bloom and his team were able to use sophisticated chemical analysis on the preserved wheat. Their analysis, which involved testing the nitrogen assimilation in three different methods, confirmed that elevated levels of atmospheric CO2 had inhibited nitrate assimilation into protein in the field-grown wheat.
The results of this experiment are consistent with experiments conducted with previous laboratory studies, which "showed that there are several physiological mechanisms responsible for carbon dioxide's inhibition of nitrate assimilation in leaves," Bloom said in the statement.
Previous studies have also shown that high levels of CO2 reduced protein concentrations in grains like wheat, barley, rice, and tubers such as potatoes by as much as eight percent.
"When this decline is factored into the respective portion of dietary protein that humans derive from these various crops, it becomes clear that the overall amount of protein available for human consumption may drop by about three percent as atmospheric carbon dioxide reaches the levels anticipated to occur during the next few decades," Bloom said.
This loss of natural nitrogen could be balanced by providing fertilizers to plants that are high in nitrates. But this method is more expensive and results in the emission of nitrous oxide, a potent greenhouse gas.
© 2012 iScience Times All rights reserved. Do not reproduce without permission.