Introduction
Description of the photosynthetic mechanisms of C3 plants:
C3 photosynthetic plants use a mechanism where the first carbon compound consists of three carbon atoms. In this process, carbon dioxide enters the plant through the stomata and undergoes multiple cycles such as the Calvin-Benson cycle, which fixes carbon dioxide. The rubisco wants to fixCarbon atoms, but it is also capable of fixin oxygen atoms. Fixing oxygen atoms creates a toxic two carbon compound. Approximately 20% of the time the rubisco fixes oxygen. When this happens the plant must start a process called photorespiration to remove toxic compunds. This causes the plant to use up energy that could have gone towards photosynthesis.
Task
Description of C4 plants
Plants have evolved in order to keep producing sugars and starches throughout high temperatures. The firsy carbon compound consists of four carbon atoms. They have a special anatomy which allows carbon to concentrate in bundle sheath cells around the rubisco. Doing this allows the carbon to be delivered right to the rubisco, meaning it will not come in contact with oxygen. Not being in contact with oxygen eliminates the chance of fixing oxygen, therefore removing the need to photorespirate and waste energy.
Process
Labelled diagram showing the C3 and C4 plant photosyntetic pathway
Evaluation
Five species of plant that undergo c3 photosyntheis are elm trees, eucalyptus, wheat, cotton,and sunflowers.
Five species that undergo c4 photosyntheis are corn, sugarcane, sorghum, crab grass, and kangaroo grass.
Conclusion
Environmental conditions the c3 are found in is cool and wet climates. They need to open their stomata in order to receive more carbon dioxide. If the climate is wet and cool, less water will leave due to transpiration. When the stomata opens to allow carbon in, they also release water. Which brings c3 plants to a disadvantage because they won’t be able to work as well through high temperatures or droughts.
Environmental conditions the c4 are found in is hot and sunny. They are able to continue to fix carbon while the stomata is closed, it doesn't matter if its hot or sunny. The less they open their stomata, the less water will leave. This means they are able to retain more water which is necessary for hot climate.
Credits
Similarities between the 2 types of photosynthetic mechanisms are that they both require RuBP and RUBISCO to complete the cycle, and both are light independent reactions. Both cycles are pathways of dark reaction of photosynthesis. All plants have the C3 cycle but the C4 cycle is only present in C4 plants.
Increased oxygen has an inhibitory effect on the C3 cycle. C4 cycle requires 30 ATP molecules to syntheis glucose when the C3 cycle only needs 18 ATP. In C4 plants there is 2 CO2 acceptors. They are PE and RuBP.