- Optical (left) plus copper X-ray false color image (right) of 50 million year old fossil leaf. False color image: colour intensity indicates relative concentration. Copper is contained within organic compounds derived from the original plant chemistry. Image width ~23 mm. Data acquired at Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the U.S. Department of Energy, Office of Basic Energy Sciences.
Professor Roy Wogelius, also of the University of Manchester and one of the senior authors said: “This type of chemical mapping and the ability to determine the atomic arrangement of biologically important elements such as copper and sulfur can only be accomplished at a synchrotron. In one beautiful specimen, the leaf has been partially eaten by caterpillars and their feeding tubes are preserved on the leaf. We see this behaviour with modern caterpillars. The chemistry of these fossil tubes remarkably still matches that of the leaf on which the caterpillars fed.”
The data from a suite of other techniques performed at the University of Manchester has lead the team to conclude that the chemistry of the fossil leaves is not wholly sourced from the surrounding environment as has previously been suggested but represents that of the living leaves.
Another reason that these specimens have been so beautifully preserved over millions of years is that they have been preserved by similar elements to those used in modern wood preservatives. Dr. Phil Manning, a senior author on the paper, added: “We think that copper may have aided preservation by acting as a ‘natural’ biocide, slowing down the usual microbial breakdown that would destroy delicate leaf tissues. This property of copper is utilised today in the same wood preservatives that you paint on your garden fence.”
Dr. Nicholas Edwards added: “This opens up the possibility to study part of the biochemistry of ancient plants, so in the future it may enable us observe the changes, if any, in the use of metals by the plant kingdom through geological time.”
Notes for editors:
A copy of the paper, ‘Leaf Metallome Preserved Over 50 Million Years,’ published in the Royal Society of Chemistry journal Metallomics, is available on request.
Additional quotes from the paper’s co-authors for use by the media:
Stanford’s Dr Uwe Bergmann, the team physicist, said: “Part of what I do involves detailed measurements of the physics of how plants actually harness light energy using transition metals. Here, we are able to show what metals were present, and where, within extremely old plants- and this just may let us understand, eventually, how the complicated physics of life has developed over long periods of time.”
Dr Bart van Dongen, a University of Manchester geochemist, said: “There is a sharp contrast in the chemistry of the fossils from that of the rock in which they are entombed – this is true for both the trace metals and the organic compounds. The organic part of the chemistry clearly shows a plant-derived component.”
Dr Nicholas Edwards added: “This opens up the possibility to study part of the biochemistry of ancient plants, so in the future, it may enable us observe the changes, if any, in the use of metals by the plant kingdom through geological time.”