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College News
16 July 2004
Turning over a new leaf: a decline in carbon dioxide sheds light on leaf evolution
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A fall in carbon dioxide
levels more than 300 million years ago is likely to have permitted
the evolution of plant leaves, a new report indicates. Researchers
have found that there is a correlation between a decrease in carbon
dioxide and a |
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Plants, which absorb carbon dioxide through stomatal pores on their leaves, were devoid of leaves when they first evolved 380 million years ago. Instead, plants absorbed the gas through limited stomatal pores located on their stems, which were sufficient because carbon dioxide levels at that time were very high. Stomatal pores also allow the evaporation of water from the leaf tissue, providing a cooling effect: the limited number of stomatal pores meant that, had leaves existed, they would have overheated. Therefore, the increase in stomatal numbers was a necessary prerequisite for leaf growth. The research team,
funded by |
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| consisted of Professor William Chaloner from Royal Holloway, University of London; Dr Colin Osborne, a Royal Society Research Fellow; and Professor David Beerling and Dr Barry Lomax from the University of Sheffield. |
A 390 million year old Devonian plant with small forked side branches,
the forerunners of leaves. True leaves evolved from such branches
as the falling carbon dioxide drove plants to produce more efficient
means of "fixing" carbon from the air. Photograph by
Dr Colin Osborne
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The research involved the examination of 300 fossil plants, covering a wide range of species, to test the hypothesis that a decline in carbon dioxide made way for leaf evolution. The team found that for two of the species, a sharp 25-fold increase in leaf size was paralleled with an eight-fold increase in stomatal density.
ENDS
Hi-res version of image (see above) is available on request.
Editor's Notes
"Biophysical constraints on the origin of leaves inferred from the fossil record," by C.P. Osborne, D.J. Beerling, B.H. Lomax, and W.G. Chaloner. Proceedings of the National Academy of Sciences, USA, Issue No. 28.
Project team:
William Chaloner is an Emeritus Professor in Botany, within the Geology
Department at Royal Holloway, University of London.
Professor David Beerling is a Professor from the Department of Animal
and Plant Sciences at the University of Sheffield.
Dr Colin Osborne is a Royal Society University Research Fellow.
Dr Barry Lomax is a Postdoctoral Associate from the Department of Animal
and Plant Sciences at the University of Sheffield.
The Leverhulme Trust
The Trust, established at the wish of William Hesketh Lever, the first
Viscount Leverhulme, makes awards for the support of research and education.
The Trust emphasises individuals and encompasses all subject areas.
For further information visit www.leverhulme.org.uk/
For further information
contact Royal Holloway, University of London,
Press Office:
Christine Long
Press & PR Officer
01784 443967, christine.long@rhul.ac.uk
Vicky Cousins
Assistant Press & Communications Officer
01784 414480, victoria.cousins@rhul.ac.uk
