A new analysis of fossilized grass-pollen grains deposited on ancient European lake and sea bottoms 16-35 million years ago reveals that C4 grasses evolved earlier than previously thought.
This new evidence casts doubt on the widely-held belief that the rise of this incredibly productive group of plants was driven by a large drop in atmospheric carbon dioxide concentrations during the Oligocene epoch.
The research team, led by University of Maryland Center for Environmental Science Appalachian Laboratory researcher Dr. David Nelson and University of Illinois Professor Feng Sheng Hu, examined the carbon isotope signatures of hundreds of grass-pollen grains and found that C4 grasses were already present on the landscape during the early part of the Oligocene, some 14 million years earlier than previously thought from geological evidence. Their findings are now published online in the journal Geology and will shortly appear in the print edition.
"The idea that C4 grasses originated prior to global decreases in carbon dioxide levels requires us to reevaluate the way we think about the evolution of C4 photosynthesis," said Dr. Nelson. "This new information should encourage the examination of alternate evolutionary selection pressures, such as warm temperatures or dry climates."
C4 plants compose only 3 percent of flowering plant species, yet account for about 25 percent global terrestrial productivity. About 60% of C4 species are grasses, and they dominate the world's grassland and savanna biomes, particularly those in warmer, lower latitude areas. Their ecological success results from the way these species concentrate and then fix carbon dioxide in order to power photosynthesis. While the most well known C4 plants are maize and sugar cane, both of which are critical to human consumption, there is a growing interest in their use as biofuels in order to capture carbon from the atmosphere to mitigate increasing global carbon dioxide levels.
The team used an innovative technique pioneered by Dr. Nelson earlier in his career - the Single Pollen Isotope Ratio Analysis or SPIRAL – to analyze the samples. The scientists first extracted grains of grass pollen from sedimentary rocks using a micromanipulator; then analyzed the tiny samples using a microcombustion device interfaced with an isotope ratio mass spectrometer in Ann Pearson's laboratory at Harvard University, which houses one of only a handful of these devices in the world. Through this analysis, they were able to detect the signature of C4 species from their more common C3 counterparts, because C4 and C3 plants take up different ratios of carbon isotopes during photosynthesis.
"SPIRAL enables us to detect C4 grasses at much lower abundances in geological records than previous approaches, which is helping to revolutionize our ability to study their ecology and evolution," said Dr. Hu. University of Illinois graduate student Michael Urban, lead author of the paper, continues to analyze samples from other parts of the world to look at variation in C4-grass abundance in relation to past changes in atmospheric CO2 and climate.
The article, "Isotopic evidence of C4 grasses in southwestern Europe during the Early Oligocene-Middle Miocene" is online at http://geology.gsapubs.org/content/early/2010/10/05/G31117.1.abstract . This research was supported by University of Illinois Research Board, National Science Foundation and the David and Lucille Packard Foundation Fellowships Program.
The University of Maryland Center for Environmental Science is the University System of Maryland's environmental research institution. UMCES researchers are helping improve our scientific understanding of Maryland, the region and the world through five research centers – Chesapeake Biological Laboratory in Solomons, Appalachian Laboratory in Frostburg, Horn Point Laboratory in Cambridge, Institute of Marine and Environmental Technology in Baltimore, and the Maryland Sea Grant College in College Park.
Christopher Conner | EurekAlert!
Safeguarding sustainability through forest certification mapping
27.06.2017 | International Institute for Applied Systems Analysis (IIASA)
Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....
A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...
Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision
Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...
21.07.2017 | Event News
19.07.2017 | Event News
12.07.2017 | Event News
21.07.2017 | Earth Sciences
21.07.2017 | Power and Electrical Engineering
21.07.2017 | Physics and Astronomy