Plant Acclimation and Adaptation to a High CO2 World

Plant adaptation to elevated atmospheric carbon dioxide (CO₂) is of great interest, as the concentration of this gas in the atmosphere has risen by more than 30% to 388 µmol mol^-1 since the industrial revolution. On average there has been a rise of 3 ppm per year.  Plant fossil samples suggest that atmospheric CO₂ may be acting as a selective agent driving evolution, but limited evidence is available to support this idea that plants subjected to future predicted concentrations of carbon dioxide may adapt. In contrast, much evidence is available on plant acclimation mechanisms and phenotypinc plasticity in future high CO₂ concentrations. Studying evolutionary responses to this aspect of environmental change is difficult, but here we use a CO₂ spring site where plants have been exposed for multiple generations to concentrations of CO₂ predicted for 2050. From this, detailed phenotyping data were collected, including data for stomatal patterning, photosynthetic performance and growth. Considerable evidence exists to show that stomatal numbers have declined across geological time and that this is linked to CO₂ concentration, but few CO₂-sensitive stomatal patterning genes have ever been identified. When grown under elevated CO₂ concentrations P. lanceolata (the narrow leaf plantain), seeds collected from the spring site showed a counter-intuitive increase in stomatal index and density. Here, in this non-model plant we have investigated the gene expression changes underlying this stomatal patterning response to elevated CO₂.

RNA-Seq allowed for in-depth analysis in P. lanceolata with no previous information required, enabling rapid evaluation of any of novel plant acclimation and adaption mechanisms. Using this approach we have identified a set of novel genes for stomatal patterning in high CO₂ and confirmed previously observed acclimation responses.