Plant Adaptations

• C3 plants


  Plants where the first stable organic compound formed in the Calvin cycle is glyceraldehyde 3-phosphate, which contains 3 carbon atoms
• Most plants put CO2 directly into the Calvin cycle
• C4 plant adaptations


  • Develop a supplementary method of CO2 uptake which forms a 4-carbon molecule called oxaloacetate
  • Have a special enzyme that can work better at very low CO2 levels to grab the CO2
  • Release the CO2 from the oxaloacetate and put it into the Calvin cycle concentrated in specialized cells (bundle sheath cells) impermeable to oxygen

  
• C4 plants


  • crabgrass
  • sugarcane
  • corn
• CAM plants


  Plants that separate their C3 and C4 cycles by time, incorporating CO2 into various organic compounds at night and then taking the CO2 from these compounds and putting it into the Calvin cycle during the day

  
• Over 8000 species of angiosperms, scattered among 18 different families, have developed adaptations which minimize the losses to photorespiration
• This is why crabgrass can stay green and keep growing when all the rest of your grass is dried up and brown
• Some plants (for example, cacti and pineapple) that live in extremely hot, dry areas like deserts, can only safely open their stomates at night when the weather is cool
• At night when they can open their stomates and take in CO2, they incorporate the CO2 into various organic compounds to store it
• In the daytime, when the light reaction is occurring and ATP is available (but the stomates must remain closed), they take the CO2 from these organic compounds and put it into the Calvin cycle