Photosynthetic Responses of Seedlings of Two Eucalyptus Species to Increases in the Atmosphere's Temperature and CO2 Concentration
Ghannoum, O., Phillips, N.G., Sears, M.A., Logan, B.A., Lewis, J.D., Conroy, J.P. and Tissue, D.T. 2010a. Photosynthetic responses of two eucalypts to industrial-age changes in atmospheric [CO2] and temperature. Plant, Cell and Environment 33: 1671-1681.
Ghannoum et al. grew individual well watered and fertilized plants of two species of Australian eucalypts -- faster-growing Eucalyptus saligna and slower-growing E. sideroxylon -- from seed in 10-L pots filled with 9 kg of loamy-sand in naturally-lit glasshouse compartments maintained at either ambient or ambient + 4°C air temperature and three different CO2 concentrations (280, 400 or 650 ppm) for a period of 140 days, while measuring various plant responses throughout the experiment.
The seven scientists report that Asat increased by ~50% with each step-increase in the air's CO2 concentration -- i.e., going from 280 to 400 ppm, and going from 400 to 650 ppm -- and that at the higher of the two temperature treatments, the optimal temperature for Asat increased by 2-7°C across the three CO2 treatments.
The Australian and U.S. researchers conclude, as they describe it, that "when water and nutrient supplies are non-limiting, photosynthesis of eucalypt seedlings is expected to strongly increase with rising CO2 concentration and temperature," while noting that their results "partly explain the strong growth responses to elevated CO2 and temperature observed in a previous study with the same eucalypt seedlings," citing the work of Ghannoum et al. (2010b).
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Ghannoum, O., Phillips, N.G., Conroy, J.P., Smith, R.A., Attard, R.D., Woodfield, R., Logan, B.A., Lewis, J.D. and Tissue, D.T. 2010b. Exposure to preindustrial, current and future atmospheric CO2 and temperature differentially affects growth and photosynthesis in Eucalyptus. Global Change Biology 16: 303-319.