A study led by University of Illinois plant biology professor Feng Sheng Hu (right), with graduate student Michael Urban, used a spooling-wire micro-combustion device (pictured) coupled with an isotope mass spectrometer to analyze individual grains of grass pollen to determine the age of C4 grasses. The study pushed back the origin of C4 plants by millions of years.
CHAMPAIGN, lll. According to a popular hypothesis, grasses such as maize, sugar cane, millet and sorghum got their evolutionary start as a result of a steep drop in atmospheric carbon dioxide levels during the Oligocene epoch, more than 23 million years ago. A new study overturns that hypothesis, presenting the first geological evidence that the ancestors of these and other C4 grasses emerged millions of years earlier than previously established. The findings are published in the journal Geology. C4 plants are more efficient than C3 plants at taking up atmospheric carbon dioxide and converting it into the starches and sugars vital to plant growth. (C3 and C4 refer to the number of carbon atoms in the first molecular product of photosynthesis. Having evolved relatively recently, C4 plants make up 3 percent of all living species of flowering plants.
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