C3 and C4 plants are two types of photosynthetic pathways that plants use to fix carbon dioxide during the process of photosynthesis. Here are five key differences between C3 and C4 plants:
Photosynthetic Pathway:
C3 Plants: Utilize the C3 photosynthetic pathway, where the first stable compound formed during carbon fixation is a three-carbon compound called 3-phosphoglycerate (PGA).
C4 Plants: Utilize the C4 photosynthetic pathway, where the first stable compound formed during carbon fixation is a four-carbon compound, typically oxaloacetate.
Enzyme Involved in Carbon Fixation:
C3 Plants: Use the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) for carbon fixation. RuBisCO is responsible for catalyzing the initial reaction where CO2 is captured and fixed.
C4 Plants: Initially fix carbon dioxide using a different enzyme called phosphoenolpyruvate carboxylase (PEP carboxylase), which has a higher affinity for CO2 than RuBisCO. The four-carbon compound formed is then transported to specialized cells where CO2 is released for the Calvin cycle.
Leaf Anatomy:
C3 Plants: Have a simpler leaf anatomy without distinct separation of photosynthetic processes. They perform both light-dependent and light-independent reactions in the mesophyll cells.
C4 Plants: Exhibit a unique leaf anatomy with a separation of the initial carbon fixation (in mesophyll cells) and the Calvin cycle (in bundle-sheath cells). This separation enhances the efficiency of carbon fixation, especially in conditions of high temperature and intense sunlight.
Adaptation to High Temperatures:
C3 Plants: Tend to be less efficient in high-temperature conditions due to the susceptibility of RuBisCO to photorespiration, a process that can reduce the efficiency of photosynthesis.
C4 Plants: Are more adapted to high-temperature environments because the C4 pathway minimizes photorespiration. The separation of carbon fixation and the Calvin cycle helps prevent the loss of carbon through photorespiration.
Geographic Distribution:
C3 Plants: Are generally found in cooler and moister climates. Many crops, such as wheat and rice, are C3 plants.
C4 Plants: Are more prevalent in warm and arid regions. Examples include maize (corn), sugarcane, and certain types of grasses.
In summary, C3 and C4 plants differ in their photosynthetic pathways, the enzymes involved in carbon fixation, leaf anatomy, adaptation to high temperatures, and geographic distribution. These adaptations contribute to the efficiency of photosynthesis and allow C4 plants to thrive in conditions that might be less favorable for C3 plants.