Carbon Metabolism in Turfgrasses

Abstract

What is known as photosynthesis is the process by which inorganic carbon (i.e., atmospheric CO2) is captured by certain living organisms and converted to organic forms, primarily carbohydrates. The general equation to synthesize one molecule of glucose (the most abundant constitutive monosaccharide) can be written as follows: 6CO2 + 6H2O → C6(H2O)6 + 6O2 The energy and reductive power necessary to make possible this highly endergonic reaction is taken by photosynthetic organisms from sunlight. A more detailed view allows division of photosynthesis into a light-dependent and a synthetic phase [1,3,4]. The former comprises the absorption of radiant energy from sunlight and its conversion into chemical intermediates containing high energy (ATP) and reductive power (NADPH). In fact, radiant energy is utilized to split the water molecule to produce oxygen and generate electrons. The transport of such electrons through specialized membranes is utilized to synthesize ATP and reduce NADP + to NADPH. The synthetic phase includes the utilization of ATP and NADPH to effectively convert inorganic CO2 into biomolecules known as photoassimilates [4]. Formerly, the carbon assimilation process was denominated the dark step of photosynthesis [3]. However, the current name “synthetic phase” is more accurate since it is not completely “dark” (meaning absolute independence from light) because it needs photogenerated ATP and NADPH, and the whole process is regulated to be operative in the light, largely by light-dependent events.