AOBPreview originally published online on December 15, 2008
Annals of Botany 2009 103(5):769-775; doi:10.1093/aob/mcn252
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Adaptive phenotypic plasticity of Pseudoroegneria spicata: response of stomatal density, leaf area and biomass to changes in water supply and increased temperature
1 Department of Natural Resource Sciences, Thompson Rivers University, Kamloops, BC, Canada
2 Department of Botany, and Biodiversity Research Center, University of British Columbia, Vancouver, BC, Canada
3 Department of Biological Sciences, Thompson Rivers University, Kamloops, BC, Canada
* For correspondence. E-mail lfraser{at}tru.ca
Received: 1 August 2008 Returned for revision: 29 September 2008 Accepted: 10 November 2008 Published electronically: 15 December 2008
Background and Aims: Changes in rainfall and temperature brought about through climate change may affect plant species distribution and community composition of grasslands. The primary objective of this study was to test how manipulation of water and temperature would influence the plasticity of stomatal density and leaf area of bluebunch wheatgrass, Pseudoroegneria spicata. It was hypothesized that: (1) an increased water supply will increase biomass and leaf area and decrease stomatal density, while a reduced water supply will cause the opposite effect; (2) an increase in temperature will reduce biomass and leaf area and increase stomatal density; and (3) the combinations of water and temperature treatments can be aligned along a stress gradient and that stomatal density will be highest at high stress.
Methods: The three water supply treatments were (1) ambient, (2) increased approx. 30 % more than ambient through weekly watering and (3) decreased approx. 30 % less than ambient by rain shades. The two temperature treatments were (1) ambient and (2) increased approx. 1–3 °C by using open-top chambers. At the end of the second experimental growing season, above-ground biomass was harvested, oven-dried and weighed, tillers from bluebunch wheatgrass plants sampled, and the abaxial stomatal density and leaf area of tillers were measured.
Key Results: The first hypothesis was partially supported – reducing water supply increased stomatal density, but increasing water supply reduced leaf area. The second hypothesis was rejected. Finally, the third hypothesis could not be fully supported – rather than a linear response there appears to be a parabolic stomatal density response to stress.
Conclusions: Overall, the abaxial stomatal density and leaf area of bluebunch wheatgrass were plastic in their response to water and temperature manipulations. Although bluebunch wheatgrass has the potential to adapt to changing climate, the grass is limited in its ability to respond to a combination of reduced water and increased temperature.
Key words: Bluebunch wheatgrass, Pseudoroegneria spicata, biomass, climate change, grassland, open top chamber, rain shade, stomata
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