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. 

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Similarities and Difference between C3 and C4 Plants – A Comparison Table


C3 vs C4 Plants Comparison

Similarities and Difference between C3 and C3 Plants
(C3 plants vs C4 plants – A Comparison Table)

Green plants are unique to possess the ability to fix light energy from sunlight through a process called photosynthesis. The photosynthesis essential involves the synthesis of carbohydrates with atmospheric carbon dioxide, water and energy obtained from the sunlight. The process of photosynthesis in plants is completed in two broad steps, 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, these energy rich molecules are used up for the synthesis of carbohydrates with carbon dioxide. There are essentially three different types of dark reaction pathways are operated in different plants on earth and they are named on the basis of the components of these pathways. They are C3 plants, C4 plants and CAM plants. The present post describes the similarities and differences between C3 plants and C4 Plants.

C3 Plants: Plants which uses C3 cycle (Calvin cycle) of dark reaction of photosynthesis. C3 cycle is the first described dark reaction pathway. Majority of the plants (~95%) on earth are C3 type. The first stable product formed in C3 cycle is a three carbon (3C) compound, hence the name. The photosynthetic efficiency of C3 plants is comparatively less due the high rate or photorespiration. For a considerable period of time, the C3 cycle was thought to be the only dark reaction pathway in plants.

C4 Plants: These plants in addition to C3 cycle, uses an additional dark reaction pathway called C4 cycle. Very few plants (~5%) on earth are C4 type. The first stable product formed in C4 cycle is a four carbon (4C) compound, hence the name. The photosynthetic efficiency of C4 plants is very high due to the absence of photorespiration. 

Similarities between C3 and C4 Plants

@. Both C3 and C4 are types of dark reactions of photosynthesis.

@. Both C3 and C4 plants fix energy from sunlight.

@. Both C3 and C4 plants synthesize carbohydrates.

@. The general equation of photosynthesis (6CO2 + 12H2O → 6C6H12O6 + 6O2 + 6H2O) is similar in both C3 and C4 plants.

@. Both C3 and C4 plants require 6 molecules of CO2 and 12 molecules of water to synthesis one molecule of glucose.

@. The carbohydrate product of both C3 and C4 cycle is a three-carbon sugar phosphate molecules called Glyceraldehyde 3 phosphate (G3P).

@. Both C3 and C4 plants requires chloroplasts for doing photosynthesis.

@. The light reaction of photosynthesis is similar in both C3 and C4 plants.

@. RuBP can accept CO2 in both C3 and C4 plants.

Difference between C3 and C4 Plants

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