IJMS | April 2016 - Browse Articles
CAM photosynthesis was named in honor of the plant family in which is was first documented, Crassulacean, the stonecrop family or the orpine family. CAM photosynthesis is an adaptation to low water availability, and it occurs in orchids and succulents from very arid regions. The process of chemical change can be that followed by either C3 or C4, in fact, there's even a plant called Agave augustifolia which switches back and forth between modes as the local system requires.
Geographic distribution of major crops across the …
In addition, our motivation was to compare the differences between C3 and C4 photosynthesis mechanism and their responses under different environments, therefore we set the objective function as maximization of CO2 fixation and biomass synthesis. Since in previous AraGEM and C4GEM, the objective was to minimize the use of light energy while achieving a specified growth rate, we need to reset some flux constraints according to biochemistry knowledge. For example, the CO2 leakage was blocked from bundle sheath to mesophyll cell with zero flux in C4GEM, which was not consistent with actual situation; here we adjusted the upper bound of this reaction to permit the leakage of CO2. In addition, because starch is not synthesized in mesophyll cell of C4 plants, the biomass components of C4GEM were also reset. The lower and upper bounds of flux in TCA cycle were adjusted as -50 and 50, to restrict flux of respiration in mitochondria. The detail of modified constraints in our improved models can be got from the Additional File.
In C4 plants, Phosphoenolpyruvate carboxylase (PEPC, EC: 18.104.22.168) notably performs the initial fixation of atmospheric CO2 in photosynthesis, which catalyzes the carboxylation of phosphoenolpyruvate (PEP) in a reaction that yields oxaloacetate and inorganic phosphate . Therefore, knockout of PEPC resulted in zero flux of biomass, which validates its crucial role in C4 photosynthesis. Pyruvate phosphate dikinase (PPDK, EC: 22.214.171.124) catalyzes the conversion of the 3-carbon compound pyruvate into phosphoenolpyruvate. Its deletion reduced the flux of CO2 fixation and biomass, which is consistent with experiment results that inhibition of PPDK significantly hinders C4 plant growth . In comparison, these two enzymes have no effect on CO2 fixation and biomass in C3 network.
Statistical Techniques | Statistical Mechanics
Some modifications to C3 plants are thought possible because comparative studies have shown that C3 plants already have some rudimentary genes that are similar in function to C4 plants. The evolutionary process that created C4 out of C3 plants occurred not once but at least 66 times in the past 35 million years. That evolutionary step achieved high photosynthetic performance and high water- and nitrogen- use efficiencies; C4 plants have twice as high photosynthetic capacity, particularly at higher temperatures as those of C3 plants, and can cope with less water and available nitrogen. For this reason, biochemists have been attempting to move C4 traits to C3 plants as a way to offset environmental changes faced by global warming.
Oklahoma City Community College
1. Compare and contrast the process of the photosynthesis in C3 and C4 plants (30%)
2. Explain how the rate oh photosynthesis is affected by the environmental factors, particularly light intensity, carbon dioxide concentration and temperature (30%).
3. Explain how crop productivity is related to photosynthesis (20%)
4. Discuss the significance of C3 and C4 photosynthesis with respect to productivity in temperate and tropical zones (20%)
The main difference between C3 and C4 plants is that ..
The C4 photosynthetic cycle supercharges photosynthesis by concentrating CO2 around ribulose-1,5-bisphosphate carboxylase and significantly reduces the oxygenation reaction. Therefore engineering C4 feature into C3 plants has been suggested as a feasible way to increase photosynthesis and yield of C3 plants, such as rice, wheat, and potato. To identify the possible transition from C3 to C4 plants, the systematic comparison of C3 and C4 metabolism is necessary.