Three Types of Photosynthesis

A general overview of the three types of photosynthesis.

      There are three different types of photosynthesis. The major difference between these types of photosynthesis is how they cope with changes in climate. C3 photosynthesis is a very well rounded system. It is very efficient when dealing with moderate climates and can somewhat handle more arid and hot regions. The problem that this type of photosynthesis encounters when placed in hot dry conditions is photorespiration. Photorespiration occurs when a C3 plant’s stomata close in response to hot weather. They close to ensure that no water is lost through evaporation. When they close the inside of the plant takes in oxygen and releases carbon dioxide. Oxygen is still being produced by the mesophyll cells, but with the stoma closed, it is being released into the inside of the cell. As this continues, the concentration of carbon dioxide decreases while the concentration of oxygen increases. When there is a significant amount of oxygen, RuPB combines with oxygen that is now present in the cell. This makes one molecule of 3PG as opposed to carbon dioxide’s out put of two 3PGs, and eventually carbon dioxide is released. The closing of the stomata results in a decrease by half of production. However, if the stomata did not close in cases such as these, then the plant would lose massive amounts of water, wilt or maybe even die. The C4 photosynthesis process solves this problem by combining a variety of improvements. The first of these is chloroplasts in the sheath bundle cells. The sheath bundle cells having chloroplasts is helpful because this allows the Calvin cycle to occur close to the vein and far from the stomata. Another improvement is the addition of a pump that moves the fixated carbon dioxide from the mesophyll cells to the sheath bundle cells. This process of pumping carbon dioxide, while requiring energy, is more efficient in the long run. The last improvement is the use of PEP instead of RuPB. This is useful because PEP does not bind with oxygen, so photorespiration does not occur in C4 photosynthesis. CAM photosynthesis is similar to C4 photosynthesis because C4 photosynthesis separates the carbon dioxide by space to ensure that none escapes. In CAM photosynthesis, carbon dioxide is separated by time. In CAM photosynthesis, the stomata are open during the nighttime when the weather is temperate. Carbon fixation occurs during this time-period.  Then, when daytime starts the Calvin cycle begins. This may make less energy then other methods but it is the best way of making energy in extreme climates. C3 photosynthesis is similar to C4 photosynthesis in the respect that they both occur without time restrictions. However, C4 photosynthesis is different from C3 photosynthesis because C4 photosynthesis separates fixation and the Calvin cycle. In this way, C4 photosynthesis is similar to CAM photosynthesis. All systems’ stomata close in response to hot weather.

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