C3 plants uses C3 cycle or Calvin cycle for dark reaction of photosynthesis. C4 plants uses C4 cycle or Hatch-Slack Pathway for the dark reaction of photosynthesis. Examples of C3 plants: Wheat, Rye, Oats, Rice, Cotton, Sunflower, Chlorella. Examples of C4 plants: Maize, Sugarcane, Sorghum, Amaranthus.