Increasing levels of carbon dioxide affect the quality of dietary crops by reducing their nutritious value, a new research states.
Researchers at University of California-Davis conducted a field test and found that rising carbon dioxide levels hold back absorption of nitrate in the plants. The assimilation or processing of nitrogen plays an important role in growth and productivity of plants.
The processing is important in food crops because plants use nitrogen to produce the proteins that are vital for human nutrition. Wheat, in particular, provides nearly one-fourth of all protein in the global human diet.
The researchers said that three different measures of nitrate absorption showed that the increased carbon dioxide levels had subdued nitrate assimilation into protein in the field-grown wheat.
The researchers studied the response of wheat to different levels of atmospheric carbon dioxide by examining samples of wheat grown in 1996 and 1997 in the Maricopa Agricultural Center near Phoenix, Arizona.
Air rich in carbon dioxide was released in the fields modelling the expected increased levels of atmospheric carbon in the next few decades. The results were compared to the control group of wheat plantings grown without treating them with carbon dioxide.
"These field results are consistent with findings from previous laboratory studies, which showed that there are several physiological mechanisms responsible for carbon dioxide's inhibition of nitrate assimilation in leaves," lead study author Arnold Bloom, a professor in the department of plant sciences at University of California-Davis, said in a press release.
Bloom also noticed that previous studies showed that protein content in wheat, rice and barley and potato tubers reduced on average by approximately 8 percent under elevated levels of atmospheric carbon dioxide.
"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 3 percent as atmospheric carbon dioxide reaches the levels anticipated to occur during the next few decades," Bloom said.
Bloom said that heavy nitrogen fertilization might partly compensate for the decline in food quality but it would also have a negative impact and drive up costs. More importantly, higher levels of nitrate might also leak in the groundwater and might cause harmful emissions of the greenhouse gas nitrous oxide.
