The effects of elevated carbon dioxide concentration on leaf growth and development in Populus

Abstract

The composition of the Earth’s atmosphere is changing. Such changes can largely be
attributed either directly or indirectly to anthropogenic activities. However, the effects
that these changes will have on terrestrial vegetation in the future, represents an area
of great uncertainty. The results that have been published in the literature have
generally concluded that elevated atmospheric carbon dioxide concentration ([eCO2])
causes increased above- and below-ground biomass compared to ambient conditions.
Members of the Populus genus have risen to the forefront of plant research into the
effects of [eCO2]. Members of the genus are extremely fast-growing, making them
suitable candidates for use as biomass energy crops. The Populus trichocarpa
sequence was released in 2006, hence unveiling a huge genetic resource to the plant
science community.
Although a large amount of studies to date have been dedicated to the effects of
[eCO2] on plant growth, few have focussed on the underlying genetic basis of the
changes. However, thanks to the genetic resources that are now freely available, this
has now been addressed. In the series of experiments presented in this thesis a
combination of morphological measurements, gene expression and protein studies
were used to assess the effects of [eCO2] on Populus leaves.
The results of the studies presented here have shown that there were some
differences in various aspects of plant growth as a result of [eCO2], although the
magnitude of the response was lower than has been reported previously in the
literature. However, there were rather few changes in transcript expression (as
assessed by microarrays) due to [eCO2]. This conclusion was reproducible across
different microarray platforms. This result was further confirmed by a proteomics
experiment, which showed that there were no proteins whose abundance differed
significantly between ambient and elevated [CO2].
It is possible that [eCO2] causes an additive effect on gene expression and hence the
sensitivity of the techniques was such that these differences could not be identified.
However, it may be possible that the plants demonstrate a plastic response to [eCO2]
and that the techniques used to assess the response were inappropriate in this case. In
such an instance, more targeted studies on particular biosynthetic pathways of interest
(such as cell wall biosynthesis) may be more appropriate for any future trials.

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