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Choose a Project: Projects Home Page 1. Atmospheric CO2 & Leaf Evolution 2. Polar Forests - Carbon Balance 3. Polar Forests - Distribution and Ecology 4. Biogenic Trace Gas Fluxes 5. The Evolution of C4 Plants 6. Palaeoceanographic changes 7. Biodiversity Response to Climate Change 8. Evolution of C4 Photosynthesis 9. Terminal Cretaceous Climate Change 10. C4 phylogenetic history

Personnel
Principal investigators:


Post-doctoral research associate:

Professor D.J. Beerling
Professor W.G. Chaloner (University of London)
www.gl.rhbnc.ac.uk/research/research.html
Dr. B. Lomax

July 2001 to June 2003

Summary
The widespread appearance of leaves, which characterize the great majority of present-day vegetation, did not occur until the close of the Devonian period, some 40 million years after simple leafless vascular plants first colonized the land in the Late Silurian/Early Devonian. Just why such a successful feature of the present-day flora took so long to emerge is a puzzling aspect of the plant fossil record. Consequently, this important, but neglected, feature of land plant evolutionary biology has continued to remain enigmatic since it was first identified over 70 years ago.
Our research addresses this issue from a theoretical and practical standpoint. It combines quantitative analyses of the effects of fossil leaf morphologies on organ energy budgets and gas exchange rates. We have shown that leaf evolution is driven by the dramatic 10-fold draw-down of atmospheric CO₂ due to plant-enhanced rock weathering and organic carbon burial (Beerling et al., 2001). This scenario raises important questions regarding the role of CO₂ in the evolution of leaves and makes predictions concerning the pattern of leaf evolution through in the Late Palaeozoic.
These questions are being addressed with a strongly interdisciplinary research programme, designed to develop our understanding of the biological and physical phenomena that fuelled leaf evolution by vascular land plants. Our investigations involve both experiments with plants grown at different atmospheric CO₂ levels, and analyses of important museum collections of Devonian fossil plants assemblages in Britain, Germany, Sweden and Belgium.

Check out our latest research findings by clicking on the logo to download the papers below:

Kenrick, P. (2001) Turning over a new leaf. Nature, 410, 309-310. 136KB

Beerling, D.J., Osborne, C.P. & Chaloner, W.G. (2001) Evolution of leaf-form in land plants linked to atmospheric CO₂ decline in the Late Palaeozoic era. Nature, 410, 352-354. 231KB

Two examples of specieswith different leaf shapes. On the left is marsh marigold (Caltha palustris), and the right is meadow buttercup (Ranunculus acris).

Studies on species such as these provide an observational basis for understanding the linkage between leaf shape, size and their energy balances.

Left: Lorophyton goense from the fossil collection of Prof. M. Fairon-Demaret at the University of Liège.
Right: Archaeopteris fissilis from the archive kept by Prof. E.M. Friis at the Stockholm Museum of Natural History (Photos, Colin Osborne).

Lorophyton bears structures thought to be the evolutionary forbearers of leaves - small, branching side-stems resembling the branching veins of a leaf, but without the infilling of mesophyll tissue that typically forms the lamina in modern leaves. This form is typical of plants found in Middle Devonian rocks, which are around 375-385 Myr old. True leaves first became widespread with the appearance of the genus Archaeopteris, the first forest tree, and typical of the Late Devonian period approximately 360-375 Myr ago. Archaeopteris fissilis had small, dissected leaves - our research examines the environmental factors that may have driven evolutionary trends in leaf shape and size.