The final product of C₄ pathway is

The correct answer is Malate.

Here is the step-by-step biological explanation of the C₄ pathway (Hatch-Slack pathway) and how it leads to the final product:

1. Introduction to C₄ Plants:
C₄ plants are adapted to dry, hot environments and have a unique leaf anatomy known as Kranz anatomy, containing two types of photosynthetic cells: mesophyll cells and bundle sheath cells. This spatial separation helps minimize photorespiration.

2. Primary CO₂ Fixation (in Mesophyll Cells):
Atmospheric carbon dioxide (CO₂) is absorbed by the mesophyll cells. The primary CO₂ acceptor is phosphoenolpyruvate (PEP), a 3-carbon compound. Under the catalysis of the enzyme PEP carboxylase (PEPcase), CO₂ combines with PEP to form oxaloacetate (OAA), a 4-carbon organic acid. This is why the pathway is named the C₄ pathway.

3. Conversion of Oxaloacetate (in Mesophyll Cells):
Oxaloacetate is unstable and is quickly converted into other 4-carbon compounds. In most C₄ plants, oxaloacetate is reduced using NADPH to form malate (in some plants, it may form aspartate). This conversion occurs in the chloroplasts of the mesophyll cells.

4. Transport and Decarboxylation (in Bundle Sheath Cells):
The synthesized malate (or aspartate) acts as the final transport and end product of the initial C₄ fixation stage in the mesophyll. It is transported from the mesophyll cells into the bundle sheath cells. Inside the bundle sheath cells, malate undergoes decarboxylation (splitting) to release CO₂ and a 3-carbon molecule, pyruvate. The released CO₂ then enters the Calvin cycle (C₃ cycle) to form glucose, while the pyruvate returns to the mesophyll cells to regenerate PEP.

Conclusion:
Therefore, the major final transport/stable product synthesized at the end of the initial C₄ carbon fixation pathway in the mesophyll before it is sent to the bundle sheath cells is malate.