What is a typical daytime CO2 target in greenhouses to boost photosynthesis?

• A. 0-100 ppm
• B. 200-400 ppm
• C. 800-1200 ppm
• D. 3000-5000 ppm

Answer: (C)

Increasing CO2 inside a greenhouse during the day boosts photosynthesis because CO2 is a raw material the plant uses to build sugars, and when light and other conditions aren’t limiting, raising CO2 speeds that process. The typical daytime target of about 800–1200 ppm hits a sweet spot: there’s enough CO2 to noticeably boost carbon fixation and growth, but not so much that the extra CO2 yields diminishing returns or wastes energy and resources.

Lower ranges like 0–100 or 200–400 ppm are too close to outdoor, ambient levels and don’t provide a meaningful boost to photosynthesis under normal daylight. Pushing CO2 much higher, such as 3000–5000 ppm, offers little additional gain and increases costs, ventilation needs, and potential safety concerns for workers and crop management. So the 800–1200 ppm range is where the benefit is real and economical during daytime operations.