CO2 (carbon dioxide) is used during photosynthesis. Energy from light is harnessed to combine CO2 from the air with water and form sugar. This sugar is used to build tissue and as a source of energy.
In many plants, including cannabis, the higher the concentration of CO2 in the air, the faster and more efficiently photosynthesis progresses under high light conditions.
Since CO2 increases sugar production, it increases the growth rate. Even as the plants are maturing they continue to grow and transform tissue. Thus, keeping CO2 on during the last stages of flowering will actually hasten maturity and increase yield. Keep enriching the air with CO2 until the plants are ready to harvest.
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