Question

Describe the mechanism of the Hatch and Slack pathway in C4 plants.

Answer 1

Photosynthesis:

1. It is the biological process by which all green plants convert light energy to chemical energy.
2. Sunlight is the ultimate source of energy.
3. In the presence of sunlight, carbon dioxide and water produces glucose.
4. Oxygen is released into the atmosphere as the byproduct of photosynthesis.

The chemical equation for photosynthesis:

6CO₂ + 6H₂O + sunlight + chlorophyll → C₆H₁₂O₆ + 6O₂

C₄ plants:

1. C₄ plants are described as having a C₄ cycle.
2. There are two different categories of photosynthetic cells in C₄ plants.
3. An outer layer of mesophyll cells and an inner ring of bundle-sheath cells surround the vascular bundle.
4. The vascular bundle is surrounded by a wreath-like, two-layered arrangement of chloroplast-bearing cells (chlorenchyma), known as Kranz anatomy.

Hatch and Slack Pathway

1. Plants in tropical desert regions follow the C₄ pathway.
2. The first product of carbon fixation is oxaloacetic acid.
3. C₄ pathway initiates with a molecule called phosphoenolpyruvate (PEP).
4. Phosphoenolpyruvate is the primary CO₂ acceptor and is seen in mesophyll cells.
5. Carboxylation takes place with the help of an enzyme called PEP carboxylation.
6. They yield a 4-C molecule called oxaloacetic acid.
7. Now oxaloacetate is converted into malic acid (transferred to mesophyll cells to bundle sheath cells).
8. Oxaloacetic acid is broken down into carbon dioxide and a 3-C molecule.
9. Carbon dioxide is utilized in the Calvin cycle.
10. 3-C molecule transferred back to mesophyll cell for PEP regeneration.