Seemann 9808753 Since the start of the industrial revolution, the concentration of C02 in the earth's atmosphere has risen by approximately 30%, primarily as a result of fossil fuel combustion and land-use changes, and is conservatively projected to double by the end of the 21st century. Photosynthesis, the major physiological process in the biosphere and the only biological process that removes a significant amount of C02 from the atmosphere, is itself extremely sensitive to C02 concentration. In the short term (hours to days) following exposure to 21st century C02 concentrations, the rate of photosynthesis is substantially increased, but in the long term (days to weeks) it may be significantly reduced as a result of an "acclimation" of photosynthesis, a process characterized by a reduction in the level of components of the photosynthetic apparatus. This acclimation phenomenon will have significant effects on both the global carbon cycle and ecosystem structure and function, but its biochemical and molecular basis are poorly understood. Furthermore, plant species may differ substantially in the extent that they may acclimate photosynthetic capacity to elevated atmospheric C02. The objectives of this research project are to: (1) understand the biochemical pathway(s) by which plants sense elevated C02 and signal changes in the expression of genes for photosynthesis; (2) identify the molecular mechanisms that in fact alter gene expression and consequently photosynthesis at elevated C02; and (3) determine the biochemical and molecular bases for species differences in photosynthetic acclimation to elevated C02,
