17.9. Seasonal responses of photosynthesis and growth of a bioenergy crop (Phalaris arundinacea L.) to climatic change under varying water regimes

Public examination of a doctoral dissertation in the field of forest sciences 

Doctoral candidate: M. Sc. Xiao Zhou

Date and venue: 17.9.2011 at 12 noon, BOR100, Joensuu campus

The aim of this study was to investigate how the elevated temperature and CO2 and varying water regimes affected the physiological characteristics and growth of a bioenergy crop, reed canary grass (Phalaris arundinacea L.). For this purpose, the plants was grown in an auto-controlled environment chamber system over two growing seasons (2009–2010) under elevated temperature (ambient + 3.5oC) and CO2 (700 μmol mol-1). The plants were also treated as three levels of soil moisture, ranging from high (100 % volumetric content), to normal (~50%) and low (~30%).

Elevated temperature stimulated the leaf photosynthesis and carbon storage in biomass during the early growth periods compared to ambient temperature, while it might result in earlier senescence and lower photosynthesis and biomass during the later periods. At the early stages of growing season, elevated temperature decreased the maximum rate of ribulose-1,5-bisphosphate carboxylase-oxygenase activity (Vcmax) and the potential rate of electron transport (Jmax) compared to ambient temperature at the lower measurement temperatures, opposite to the higher measurement temperatures. Later in the growing period, Vcmax and Jmax were under the elevated temperature consistently lower across the measurement temperatures. CO2 enrichment significantly increased the photosynthesis and slightly decreased Vcmax and Jmax compared to ambient CO2 across the measurement temperatures. CO2 enrichment led also to a slight down-regulation in the leaf nitrogen, chlorophyll content and fluorescence characters.

Low soil moisture decreased clearly the photosynthesis performance and chlorophyll fluorescence, which eventually also decreased the carbon storage in plant biomass, particularly under the elevated temperature. Furthermore, Vcmax and Jmax decreased significantly under low soil moisture. Nevertheless, the temperature- and drought-induced stresses were partially mitigated by the elevation of CO2.

To conclude, the seasonal estimation of the physiological and growth parameters for reed canary grass makes it possible to simulate its photosynthesis and carbon storage in biomass over the whole growing season under varying environmental conditions. The growth of plants on organic soils could also be expected to be favored under warming climate if the water availability is high.

The doctoral dissertation of M.Sc. Xiao Zhou entitled “Seasonal responses of photosynthesis and growth of a bioenergy crop (Phalaris arundinacea L.) to climatic change under varying water regimes” will be examined at the Faculty of Science and Forestry, the University of Eastern Finland. The opponent in the public examination is Professor Bjarni Diðrik Sigurðsson, the Faculty of Environment, the Agricultural University of Iceland, and the custos is Professor Seppo Kellomäki, Faculty of Science and Forestry, the University of Eastern Finland.

Photo available for download at http://www.uef.fi/vaitoskuvat

Contact: Xiao Zhou, xiao.zhou@uef.fi

Publishing year: 2011

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