The study looked at how C4 plants use oxygen during photosynthesis. They used mutants of two plant species to see how different factors affect photosynthesis. They found that C4 plants need less oxygen than previously thought for optimal photosynthesis. When C4 plants have limited CO2, they can reduce the negative effects of high oxygen levels. This shows that C4 plants need to balance their C3 and C4 cycles for best results.