| Summary
Land plants first evolved in the ancient high CO2
'greenhouse' world of the Devonian, some 400 million years
ago. High atmospheric CO2 concentrations strongly
influence stomatal development, and regulate important metabolic
processes. We hypothesize that high CO2 was a necessary
prerequisite for terrestrial plant evolution. The earliest
vascular land plants were very small, and typically possessed
short, cylindrical branched photosynthetic stems with very
few stomata. How did the stomata on the stems of these long-extinct
plants respond to fluctuating environmental conditions and
influence plant carbon and water balance ? Early non-vascular
land plants such as mosses, which also appeared in the high
CO2 world of the Devonian, possess stomata confined
only to the spore-containing photosynthetic capsules. The
stomata are 'fixed' open and do not respond to changes in
the environment. In this sense they might provide a crude
analogue for studying the stomata of early land plants.
These key questions, relating plant evolutionary biology to
physiological and molecular ecology, are being addressed in
a series of controlled environment experiments with Psilotum
nudum, a species with close morphological similarities to
early land plants (upright photosynthetic stem, few stomata),
and a range of different bryophyte taxa. We use a range of
physiological and molecular techniques, to develop an understanding
of the fundamental relationship between stomatal function
and plant performance in simulated high CO2 Devonian
atmosphere. The work will provide a crucial basis for our
understanding of the role played by atmospheric CO2
in allowing plants to colonize the land surface. |
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