Abstract
The aboveground growth, physiological and biochemical parameters of two clones of the cosmopolitan wetland grass Phragmites australis, grown at four treatment combinations of temperature and CO2, were investigated to elucidate whether their climate response differed due to inherent differences in their ecological adaptation. The two phylogeographically distinct P. australis clones (DK clone, European genetic background; ALG clone, Mediterranean genetic background) were grown for 151 days in phytotrons at 19/12 °C (day/night temperature) and 390 ppm CO2, and at elevated temperature (+5 °C) and CO2 (700 ppm) with treatment factors alone or in combination. The ALG clone had 2–4 times higher aboveground biomass, higher light-saturated rates of photosynthesis (Pmax), maximum electron transport rates (ETRmax) and Rubisco activity, and higher photosynthetic nitrogen-use efficiency than the DK clone. The DK clone, however, produced more shoots, leaves and side-shoots, and had 9–51 % higher specific leaf area and 15–39 % higher leaf nitrogen concentration than the ALG clone. Although elevated atmospheric CO2 alone barely affected the aboveground growth of the two P. australis clones, simultaneously elevated temperature and CO2 stimulated growth and aboveground biomass. Overall, elevated CO2 stimulated photosynthesis, but the clones responded differently to a concomitant increase in CO2 and temperature, depending on the phylogeographic background of the plant. The DK clone showed overall stronger responses, and can be considered the more plastic of the two clones with respect to CO2 and temperature. Thus, the DK clone may be better adapted to climate change than the ALG clone, at least in the short term.
Highlights
Temperature and atmospheric carbon dioxide (CO2) are key environmental parameters affecting plant growth, development and function, and both have changed in the recent past
Clevering et al (2001) showed that P. australis originating from higher latitudes, such as the DK clone, developed a higher number of shoots and leaves, and larger specific leaf area (SLA) compared with genotypes from lower latitudes, such as the ALG clone
Elevated temperature produced an increase in aboveground growth, regardless of the atmospheric CO2 concentration, suggesting that the ubiquitous range of P. australis will persist in the foreseeable warmer world
Summary
Temperature and atmospheric carbon dioxide (CO2) are key environmental parameters affecting plant growth, development and function, and both have changed in the recent past. Long-term exposure of plants to elevated CO2 has in some studies resulted in a stimulation of productivity and growth (Wand et al 1999; Lee et al 2010), but in other studies no significant effect has been observed (Milla et al 2006; Kim and Kang 2008). As climate factors will change concomitantly, understanding their combined effects on a species is crucial for predicting future plant responses
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