Introduction
There are two major types of photosynthesis: C3 photosynthesis and C4 photosynthesis
C3 photosynthesis is the typical photosynthesis tha most plants use and that everyone learns about in school (it was all we knew about until a few decades ago).
C4 photosynthesis is adaptation to arid conditions because it results in better water use efficiency. In addition, C4 plants can photosynthesize faster under the desert's high heat and light conditions than C3 plants because they use an extra biochemical pathway and special anatomy to reduce photorespiration.
Task
In this quest i will show major differences between theese two types of photosynthesis.
And a cake.
Process
C3 Photosynthesis :
- Called C3 because the CO2 is first incorporated into a 3-carbon compound.
- Stomata are open during the day.
- RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO2.
- Photosynthesis takes place throughout the leaf.
- Adaptive Value: more efficient than C4 plants under cool and moist conditions and under normal light because requires less machinery (fewer enzymes and no specialized anatomy)..
- Most plants are C3: rice, wheat, barye, rye, oat, soybean, cotton, tabacco, spinach, potato, peanut...
C4 Photosynthesis :
- Called C4 because the CO2 is first incorporated into a 4-carbon compound.
- Stomata are open during the day.
- Uses PEP Carboxylase for the enzyme involved in the uptake of CO2. This enzyme allows CO2 to be taken into the plant very quickly, and then it "delivers" the CO2 directly to RUBISCO for photsynthesis.
- Photosynthesis takes place in inner cells (requires special anatomy called Kranz Anatomy)
- Adaptive Value:
- Photosynthesizes faster than C3 plants under high light intensity and high temperatures because the CO2 is delivered directly to RUBISCO, not allowing it to grab oxygen and undergo photorespiration.
- Has better Water Use Efficiency because PEP Carboxylase brings in CO2 faster and so does not need to keep stomata open as much (less water lost by transpiration) for the same amount of CO2 gain for photosynthesis.
- C4 plants include several thousand species in at least 19 plant families. Example: fourwing saltbush, corn, sugarcane, sorghum, millets, switchgrass, nutsedge, couch or bermuda grass, barnyard grass.
Evaluation
We compared C3 and C4 metabolic networks using the improved constraint-based models for Arabidopsis and maize. By graph theory, we found the C3 network exhibit more dense topology structure than C4. The simulation of enzyme knockouts demonstrated that both C3 and C4 networks are very robust, especially when optimizing CO2 fixation. Moreover, C4 plant has better robustness no matter the objective function is biomass synthesis or CO2 fixation. In addition, all the essential reactions in C3 network are also essential for C4, while there are some other reactions specifically essential for C4, which validated that the basic metabolism of C4 plant is similar to C3, but C4 is more complex. We also identified more correlated reaction sets in C4, and demonstrated C4 plants have better modularity with complex mechanism coordinates the reactions and pathways than that of C3 plants. We also found the increase of both biomass production and CO2 fixation with light intensity and CO2 concentration in C4 is faster than that in C3, which reflected more efficient use of light and CO2 in C4 plant. Finally, we explored the contribution of different C4 subtypes to biomass production by setting specific constraints.
Conclusion
So, basicakky, in contrast to C3, C4 plants have less dense topology, higher robustness, better modularity, and higher CO2 and radiation use efficiency.
They are just better suited for certain circumstances.
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