Nuts over CO2
For many Americans, the end of baseball season also marks the end of peanut-eating season. But for the rest of the world, peanut season never ends: Peanuts are used not only as food, but for pharmaceuticals, soaps, cold creams, lubricants, emulsions for insect control, diesel engine fuel, dyes, and paints. Young leaves and tips are suitable as a cooked green vegetable; scorched seeds may serve as a coffee substitute. Peanut hulls are used for fuel, as a filler for fertilizers, and for livestock feed.
Given the importance of peanuts as an agricultural crop, it is valuable to anticipate the peanut?fs future as temperatures rise. Peanut plants are frost-sensitive and seem to favor higher temperatures.
But how might higher levels of atmospheric carbon dioxide (CO2) concentrations affect these versatile plants? The latest study comes from a team of British and Canadian scientists who grew peanuts in five controlled glasshouses at the University of Nottingham. They maintained atmospheric CO2 at the current natural level of 375 parts per million (ppm) and at 700 ppm, with air temperatures at 28?› C and 32?›C; some plants were irrigated throughout the growing season, while others had water withheld for 22 days following sowing.
Clifford and colleagues found that peanuts not only thrive in higher temperatures, but also in higher levels of atmospheric CO2, particularly in the face of drought. In the 28?›C chambers, elevated CO2 increased total pod biomass by only 5 percent for irrigated plants, but by 111 percent for the droughted plants. At 32?›C, the elevated CO2 increased pod biomass by 102 percent for the irrigated plants and by 125 percent for the water-stressed plants. The authors reported that the values of net photosynthesis were consistently greater under elevated CO2 in both irrigated and droughted plants.
What?fs more, they report, increases in water-use efficiency under elevated CO2 prolonged photosynthetic activity during drought and increased pod yields relative to plants grown under ambient CO2.
As with most crops grown throughout the world, elevated CO2 causes peanuts to grow larger, produce more crop for market, increase water-use efficiency, and increase tolerance to drought.
With so many benefits, it?fs hard not to go nuts for CO2!
Robert C. Balling Jr., Ph.D. is director of the Laboratory of Climatology at Arizona State University and coauthor of The Satanic Gases.
Clifford, S.C., et al., 2000. Effect of elevated CO2, drought and temperature on the water relations and gas exchange of groundnut (Arachis hypogaea) stands grown in controlled environment glasshouses. Physiologia Plantarium, 110, 78-88.