Final answer:
C4 plants possess two distinct photosynthetic cells: mesophyll and bundle sheath cells, where the C4 pathway partition CO2 fixation between these cells to efficiently synthesize sugars with reduced water loss, enhancing survival in arid conditions.
Step-by-step explanation:
The two distinct types of photosynthetic cells in C4 plants are mesophyll cells and bundle sheath cells. C4 plants have a specialized anatomy and biochemical pathway that achieves efficient photosynthesis under high heat and dry conditions.
In C4 plants, the process of photosynthesis begins in the mesophyll cells where the enzyme PEP carboxylase catalyzes the formation of a four-carbon compound (like malic acid) from a three-carbon compound (phosphoenolpyruvate). This four-carbon compound is then transported to the bundle sheath cells.
Here, the compound is decarboxylated to release CO2, which is then fixed into sugars via the Calvin cycle in these chloroplasts by the enzyme Rubisco. This mechanism increases the concentration of CO2 around Rubisco, substantially reducing photorespiration and enhancing the efficiency of carbon fixation, especially under conditions of stress, high temperatures, and low CO2 concentrations. Therefore, the C4 pathway contributes to the adaptive success of these plants in arid environments.