Photosynthesis involves the coordinated operation of a series of biochemical and biophysical reactions starting with the absorption of photons and ending with the incorporation of inorganic carbon into stable organic compounds. All algae and the cyanobacteria, as well as terrestrial vascular plants, evolve oxygen during the light reactions that produce reductant (NADP+ → NADPH) and adenosine triphosphate (ATP). These products of the light reactions are subsequently consumed in CO2 fixation by the photosynthetic carbon reduction cycle (PCRC). Competing with photosynthetic carbon reduction for NADPH and ATP are other processes, including photorespiration, nitrate reduction, mediated ion and gas transport between algal cell and environment, and various maintenance and synthetic processes. Although photosynthetic physiology can be conceptually isolated from the remainder of algal metabolism and in vitro separation of light and dark reactions of isolated chloroplasts has been accomplished (Trebst et al., 1958), in practice photosynthesis occurs simultaneously with, and cannot be separated from, the remainder of algal growth and maintenance processes. This complexity can lead to some confusion in the operational definition of the rate of photosynthesis.
KeywordsInorganic Carbon Calcium Carbonate Precipitation Total Inorganic Carbon Carbonate Alkalinity Apparent Oxygen Utilization
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