The Photosynthetic Assimilation of Nitrate and Its Interactions with CO2 Fixation

Abstract

Photosynthesis is usually identified with the light--driven formation of carbohydrates and oxygen from CO2 and water. This formulation ignores, however, the basic fact that in the photosynthetic process not only CO2, but also the oxidized forms of other primordial bioelements are reduced and incorporated into cell material. Actually, photosynthesis drives a number of biosynthetic pathways involved in the assimilation of inorganic carbon, nitrogen and sulfur. At the expense of sunlight energy, unstable energy-rich products -cell material and oxygen- are synthesized from fully oxidized substrates with no useful chemical potential, namely water, carbon dioxide, nitrate, sulfate and phosphate (Losada and Guerrero, 1979; Losada et al., 1987).