C₃ vs C₄ CO₂ Saturation Points — NEET Biology
📚 Practice ConceptThe C₃ and C₄ plants respond differently to CO₂ concentrations. At low light conditions neither group responds to high CO₂ conditions. At high light intensities, both C₃ and C₄ plants show increase in the rates of photosynthesis. What is important to note is that the C₃ plants show saturation at about 360 µlL⁻¹ while C₄ responds to increased CO₂ concentration and saturation is seen only beyond 450 µlL⁻¹. Thus, current availability of CO₂ levels is limiting to the C₃ plants.
Which of the following statements regarding C₃ and C₄ plants are correct? S1: C₄ plants exhibit Kranz anatomy, characterized by large bundle sheath cells having numerous chloroplasts, thick walls impervious to gaseous exchange, and no intercellular spaces. S2: In C₃ plants, the primary CO₂ acceptor is RuBP, and the first stable fixation product is a 3-carbon organic acid, 3-PGA, formed in the mesophyll cells. S3: C₄ plants have a mechanism that increases the concentration of CO₂ at the RuBisCO site in bundle sheath cells, thereby minimizing its oxygenase activity and preventing photorespiration. S4: The initial carboxylation reaction in C₄ plants is catalyzed by PEP carboxylase in the mesophyll cells, an enzyme that completely lacks oxygenase activity. S5: Under high light intensities, C₃ plants show saturation at about 360 µlL⁻¹ CO₂ concentration, whereas C₄ plants respond to increased CO₂ concentration and show saturation only beyond 450 µlL⁻¹. Choose the correct option:
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