Carbon Fixation

* Explain how CO2 enters leaves. What environmental factors control stomatal movement? How are these factors related to physical and chemical properties that control the opening and closing of stomata?

CO2 enters leaves through stomata, which are small openings in the leaves surrounded by guard cells. These stomata are responsive to light, so they open with natural light and close at night. One interesting environmental factor that can control stomatal movement is the overall level of CO2 in the air. When an environment is devoid of carbon dioxide, the stomata will not necessarily close in the dark. Likewise, if there exists a great amount of carbon dioxide in the air, the stomata will close even if it is light outside. This has to do with osmosis and diffusion, and the fact that the guard cells are constantly “alert” for effectively managing the amount of carbon dioxide a plant should take in, as well as the release of water vapor and oxygen into the air (Mauseth, 2014).

* What are primary stages in the photosynthetic carbon reduction (PCR) cycle? Explain the role of each stage. Draw a diagram of the stages by utilizing drawing tools in Microsoft® Word to aid your explanation.

1. Fixation – carbon dioxide is taken into the plant through the use of the carbon acceptors (RuBP). The result is a three-carbon acid.

2. Reduction – consumes NADPH and some ATP. The three-carbon acid is converted again, this time to a tri-phosphate.

3. Regeneration – the rest of the ATP is consumed. The tri-phosphate is also converted back into RuBP, which means the plant can go on accepting carbon dioxide to start the cycle again.

Fixation

Carbon dioxide + RuBP = Fixation

Reduction

Three-carbon acid + consumption of NADPH and ATP = tri-phosphate

Regeneration

ATP consumption = tri-phosphate converts to RuBP

* Explain how the ATP and NADPH produced by the photosynthetic electron transport chain are used in the PCR cycle.

NADPH and ATP are...