Carbon dioxide

• About 40% of the dry matter of the plant is composed of carbon.
• Under normal conditions, carbon dioxide(CO2) exits as a gas in the atmospheres lightly above 0.03% or 345ppm
• During the day, when photosynthesis occurs under natural light, the plants in a greenhouse draw down the level of CO2to below 200ppm.
• Under these circumstances, infiltration or ventilation increases carbon dioxide levels, when the outside air is brought in, to maintain the ambient levels ofCO2.
• In cold climates, maintaining ambient levels of CO2by providing ventilation may be uneconomical, due to the necessity of heating the incoming air in order to maintain proper growing temperatures.
• In such regions, enrichment of the greenhouse withCO2 is followed.
• The exact CO2 level needed for a given crop will vary, since it must be correlated with other variables in greenhouse production such as light, temperature, nutrient levels, cultivar and degree of maturity.
• Most crops will respond favorably to Co2 at 1000 to1200 ppm.