Elevated CO2: growth, photosynthesis and nutrient relations of Poa Alpina L. [abstract]

The growth of whole plants responds to elevated CO, less than does the initial rate of photosynthesis. The reduction in photosynthesis is often greatest at low nutrient availability. In many plants, foliar N concentrations are lower than in controls at ambient CO,. Criteria are needed to distinguish between low N causing low photosynthesis. and down-regulation of photosynthesis resulting in reduced leaf N concentration via reduction in amount of Rubisco and other proteins. We present and assess a number of criteria and experimental evidence in support of their use in relation to whole plant growth and photosynthesis of source leaves of the arctic alpine grass Poa alpina. Plants were grown to maturity (50d) in outdoor open-top chambers or in indoor controlled environment cabinets at low and high availabilities of nitrogen and phosphorus.