Difference between Mesophyll and Bundle Sheath Cells and Chloroplasts in C4 Plants

chloroplast variation of C4 plants

Differences between Mesophyll and Bundle Sheath Cells and Chloroplasts in C4 Plants
Mesophyll vs Bundle Sheath Chloroplasts: A Comparison Table)

The C4 cycle or Hatch and Slack pathway of dark reaction of photosynthesis are characterized by two structurally and functionally different chloroplasts in their leaves. The leaves of C4 plants such as maize possess the classical Kranz anatomy. In Kranz anatomy, each vascular bundle is surrounded by a ring of bundle sheath cells, followed by one or more concentric layers of mesophyll cells. Bundle sheath cells have thick cell walls and contain centrifugally arranged chloroplasts with large starch granules and unstacked thylakoid membranes, whereas the mesophyll cells contain randomly arranged chloroplasts with stacked thylakoids and little or no starch grains.

The mesophyll chloroplasts in C4 plants are highly specialized to do the light dependent reactions of photosynthesis whereas the bundle sheath cells are specialized to perform the light independent reactions. In C4 cycle, the atmospheric CO2 is first accepted by PEP in the cytoplasm of the mesophyll cells and converted to OAA with the help of the enzyme PEP carboxylase. OAA is then transported from the mesophyll cells to the bundle sheath cells. In the bundle sheath cells, OAA releases molecular CO2 and which is accepted by the regular RuBP to run the Calvin cycle or C3 cycle for the synthesis of carbohydrate precursors. 

Continue reading

Difference between C3 and C4 Cycles of Photosynthesis in Plants

C3 vs C4 Cycles of Photosynthesis

Similarities and Differences between C3 and C4 Cycles: A Comparison Table
(Calvin Cycles Vs Hatch and Slack Cycle)

Photosynthesis is one of the vital events in the earth in which the green plants fix the energy from the sunlight and synthesis nutrients with carbon dioxide and water. Almost all living things on earth, either directly or indirectly, depend on photosynthesis for energy. The process of photosynthesis in plants is completed in two major pathways, a light dependent ‘Light Reaction’ and a light independent ‘Dark Reaction’. In the light reaction, the chlorophyll molecules in the plants absorb energy from sunlight and synthesize energy rich chemical molecules such as ATP and reduced coenzymes (NADPHH+). In the dark reaction, this energy rich molecules are used up for the synthesis of carbohydrates from carbon dioxide. The first describe dark reaction pathway, better known as Calvin cycle (Melvin Calvin who discovered this pathway), is called C3 cycle. For a considerable period of time, the Calvin cycle (C3 cycle) was thought to be the only dark reaction pathway in plants. Later, a new pathway of dark reaction called Hatch and Slack pathway or C4 cycle was described in some plants. Both these cycles (C3 and C4 cycles) show many similarities and differences. The present post describes the similarities and differences between C3 cycle and C4 cycle of the dark reaction of photosynthesis.

Similarities between C3 cycle and C4 cycle

Ø  Both C3 and C4 cycles are pathways of dark reaction of photosynthesis.

Ø  Both are light independent reactions.

Ø  Both C3 and C4 cycle requires energy from ATP or reduced coenzymes.

Ø  Both C3 and C4 plants accept carbon dioxide to perform dark reaction.

Ø  End products of C3 and C4 cycle are similar.

Ø  Both C3 and C4 cycle requires RuBP and RUBISCO to complete the pathway.

Difference between C3 cycle and C4 cycle:

Continue reading