In maize and sugarcane, malate is the primary product in mesophyll cells. This malate is rapidly transported to the bundle sheath cells, where it is decarboxylated by malic enzyme to form

The correct answer is pyruvate and CO₂

Concept:

• In maize and sugarcane, which are C4 plants, the process of photosynthesis occurs in a specialized manner to efficiently fix carbon dioxide.
• These plants have unique leaf anatomy with mesophyll cells and bundle sheath cells, which work together to minimize photorespiration and maximize photosynthesis.
• In the mesophyll cells, CO₂ is initially fixed into a four-carbon compound, oxaloacetate, by the enzyme phosphoenolpyruvate carboxylase (PEP carboxylase).
• Oxaloacetate is then converted to malate, which is transported to the bundle sheath cells.
• In the bundle sheath cells, malate is decarboxylated by malic enzyme to release CO₂ and pyruvate.
• The released CO₂ is then fixed again by the Calvin cycle in the bundle sheath cells.

Explanation:

• Option 1: Oxaloacetate and CO₂ - This option is incorrect because oxaloacetate is the initial product formed in the mesophyll cells, not the product of decarboxylation in the bundle sheath cells.
• Option 2: Phosphoenolpyruvate and CO₂ - This option is incorrect because phosphoenolpyruvate (PEP) is the substrate used by PEP carboxylase to fix CO₂ in the mesophyll cells, not the product of decarboxylation.
• Option 3: Pyruvate and CO₂ - This is the correct answer. Malate is transported to the bundle sheath cells, where it is decarboxylated to produce pyruvate and CO_2. The CO₂ is then used in the Calvin cycle.
• Option 4: Phosphoglycerate - This option is incorrect because phosphoglycerate (PGA) is an intermediate in the Calvin cycle, not the product of malate decarboxylation in the bundle sheath cells.