Which of the following is the most significant limit on photosynthesis? Why?

A) chloroplast

B) light

C) water

D) carbon dioxide

D) carbon dioxide; the atmosphere is only 0.035% CO₂

Photorespiration

• wastes energy
• causes loss of fixed carbon
• makes rubisco unavailable for photosynthesis

form of photosynthesis where photorespiration is almost eliminated, divides location of dark reactions between the mesophyll and the bundle sheath

PEP

• is more efficient at binding/fixing low carbon dioxide concentration
• has no affinity for oxygen

What are some examples of C₄ plants?

What are the two stages in C₄ photosynthesis?

• 1^st  Stage:  location: mesophyll, enzyme:  PEP carboxylase
• 2^nd Stage:  location:  bundle sheath, enzyme:  rubisco

Calvin Cycle Process in C₄ Plants

1. Carbon dioxide diffuses into _________ and binds with ________.
2. PEP carboxylase and energy facilitate the creation of _____ molecules.
3. These molecules are transported into the ________.
4. CO₂ and __ molecules are released.
5. ___ goes into the Calvin Cycle; __ molecules go back to PEP
6. Calvin Cycle produces sugar that goes into the _______

1. mesophyll, PEP
2. C₄ molecules
3. bundle sheath
4. C₃
5. CO₂, C₃
6. phloem

• bundle sheath blocks oxygen; RuBP not distracted
• Photosynthesis is 2-3x more efficient than C₃ photosynthesis in hot, dry areas

Process of CAM Photosynthesis

At night, the _______ open to let in carbon dioxide, which bonds with _______.  PEP carboxylase and energy cause the production of ___ acids.  These acids are stored in the ________.  During the day, the stomata close and ___ acids are released.  __ goes into the Calvin Cycle and __ molecules go back to PEP.

stomata, PEP, C₄, vacuole, CO₂, C₄