Three Modes of Photosynthesis, Essay Example

The three different types of photosynthesis include C3, C4, and CAM (Marietta, n.d.). C3 photosynthesis is the conventionally studied mode of photosynthesis in which carbon dioxide is incorporated into a 3 carbon molecule. Rubisco is involved in the uptake of carbon dioxide. Plants that use this form of photosynthesis have stomata open during daylight hours. According to the energy value of this process, C3 photosynthesis has the highest adaptive value because it is the most efficient process; it requires fewer enzymes that are necessary in C4 and CAM and there are no specialized compartments of the plant necessary for chemical reactions. Most plants in nature use C3 photosynthesis for survival. An advantage of C3 photosynthesis is that it is highly efficient in terms of enzyme use, but it does not allow idling for energy conservation.

C4 photosynthesis is a recently discovered process in which carbon dioxide is incorporated into a 4 carbon molecule. PEP Carboxylase is the molecule involved in the uptake of carbon dioxide. This enzyme then sends the carbon dioxide to rubisco quickly for further processing. Plants that use this form of photosynthesis have stomata open during daylight hours. This process takes place within specialized cells referred to as Kranz leaf anatomy. The advantage of this mode of photosynthesis is that the photosynthesis process is quicker compared to C3 plants. Furthermore, the carbon dioxide does not undergo photorespiration because it is unable to interact with oxygen in the short amount of time it is given to interact with rubisco. Stomata also do not need to be open as long during C4 photosynthesis, which leads to water efficacy due to the smaller quantity of water that is able to evaporate at the expense of light absorption. A disadvantage is that the metabolic process of C4 photosynthesis is less direct than C3 photosynthesis. At least 19 plant families utilize C4 photosynthesis.

CAM was discovered in Crassulaceae and therefore stands for Crassulacean Acid Metabolism (PIMA Community College, n.d.). Prior to being used in photosynthesis, the carbon dioxide is stored as an acid. In these plants, the stomata tend to open at nighttime only because water evaporation is less likely to occur at nighttime temperatures. Stomata are closed during daytime hours to prevent against water loss. During the day, the carbon dioxide that has been stored as an acid is broken down and sent to interact with rubisco to perform photosynthesis. A major advantage associated with CAM photosynthesis is that it is maximally water efficient compared to C3 and C4 because the stomata is only open at night. Furthermore, when arid conditions are present, plants that use CAM photosynthesis can keep the stomata closed day and night to prevent water loss during extreme weather conditions. One disadvantage is that this process has high energy costs, so it is necessary for CAM plants to become active once again when water sources are available. As a consequence, CAM plants are most likely to thrive in desert regions. The most well-known type of CAM plants are cacti and orchids.

Overall, it appears that each mode of photosynthesis is used for plants that need to adapt to different environments. The time in which the stomata is open helps regulate water maintenance, which is more challenging in hotter and dryer regions. Understanding the different types of photosynthesis is important in understanding the biology of unique plants.

References

Marietta. (n.d.). Photosynthesis – An Overview. Retrieved from http://www.marietta.edu/~biol/biomes/photosynthesis.htm

Pima Community College. (n.d.). Types of Photosynthesis. Retrieved from http://wc.pima.edu/~bfiero/tucsonecology/plants/plants_photosynthesis.htm