C4 Plants

C₄ Plants: Plants that use a supplementary method of CO₂ uptake to form a four-carbon sugar compound. Photosynthesis in these plants involves the reaction of CO₂ with C₃ phosphoenolpyruvate (PEP) to form C₄ oxaloacetatic acid (OAA), which is converted into malic acid. Malic acid is then broken down into CO₂ (which enters the Calvin Cycle to form sugars and starch) and pyruvic acid (3-carbon molecule), which is then converted back to PEP. C₄ plants are well adapted for habitats with high daytime temperatures and intense sunlight. The ¹²C/¹³C ratio of C₄ plants is distinct and can be determined from masspectrometry. C4 plants have less ¹²C but more ¹³C compared to C₃ Plants. The ¹³C in C₄ tissue is still less than what naturally occurs in the atmosphere. e.g. Tropical grasses, including crabgrass, corn, sugarcane, sorghum.