By looking at their anatomy,
in C3 plants,
- bundle sheath cells do not contain chloroplasts;
- carbon fixation and Calvin Cycle reactions occur in mesophyll cells
- (and in the presence of oxygen).
- more adapted to environments with more carbon dioxide.
In C4 plants,
- the bundle sheath cells contain chloroplasts;
- carbon is fixed in mesophyll cells too, then transported to bundle sheath cells where
- Calvin Cycle reactions occur in the absence of oxygen.
- more adapted to environments with more oxygen
In both, photosynthesized sugars then enter the plant's vascular system.
C4 have a concentric arrangement of the bundle sheath and mesophyll layer, the bundle sheath is also thicker.
Another difference is their intervenial distances, from one bundle sheath to another you have in C4 only around 4 mesophyll cells but on 3 they are separated by 12.
C3 Photosynthesis : C3 plants.
• Called C3 because the CO2 is first incorporated into a 3-carbon compound.
• Stomata are open during the day.
• RUBISCO, the enzyme involved in photosynthesis, is also the enzyme involved in the uptake of CO2.
• Photosynthesis takes place throughout the leaf.
• Adaptive Value: more efficient than C4 and CAM plants under cool and moist conditions and under normal light because requires less machinery (fewer enzymes and no specialized anatomy)..
• Most plants are C3.
C4 Photosynthesis : C4 plants.
• Called C4 because the CO2 is first incorporated into a 4-carbon compound.
• Stomata are open during the day.
• Uses PEP Carboxylase for the enzyme involved in the uptake of CO2. This enzyme allows CO2 to be taken into the plant very quickly, and then it "delivers" the CO2 directly to RUBISCO for photsynthesis.
• Photosynthesis takes place in inner cells (requires special anatomy called Kranz Anatomy)
• Adaptive Value:
o Photosynthesizes faster than C3 plants under high light intensity and high temperatures because the CO2 is delivered directly to RUBISCO, not allowing it to grab oxygen and undergo photorespiration.
o Has better Water Use Efficiency because PEP Carboxylase brings in CO2 faster and so does not need to keep stomata open as much (less water lost by transpiration) for the same amount of CO2 gain for photosynthesis.
• C4 plants include several thousand species in at least 19 plant families. Example: fourwing saltbush, corn, and many of our summer annual plants.
Examples:
C3----->wheat, barley, potatoes and sugar beet. (most of the plants are C3)
C4----->fourwing saltbush, corn ,many of summer annual plants.
CAM---> cactuses, aloe vera, some orchids and bromeliads (required less water)
