The benefits of introducing CO2 into a grow space are well known and widely accepted. However, if you’re a novice grower and/or under a tight budget, there might be a number of ways for you to initially increase your yields before investing in a costly CO2 system. Make sure you first know how to:
Plants extract CO2 from the atmosphere via the plant’s stomates, which are the pores that plants “breathe” through. Photosynthesis begins as the plant uses CO2 in combination with light bulbs or light from the sun to produce both sugar and oxygen. The sugar is used by the plant to grow while the oxygen is released back into the atmosphere.
Who Should Use CO2 Systems for Cannabis?
CO2 generators, which look something like patio heaters, produce carbon dioxide by burning propane or natural gases. They can be set up to automatically power on or off when CO2 levels reach a specific ppm. Natural gas or liquid propane are very easy to acquire, but the burning of these gases produces heat which can be difficult to regulate in small grow spaces. Because of this, CO2 generators are better suited for large grow spaces with equipment for climate control.
How Does CO2 Work for Plants?
Most gardeners have found that when you are producing high-quality light in your garden, a CO2 level of 1,200 to 2,000 ppm will increase the growth of your plant significantly. Additionally, when using CO2 your plants can handle a higher average temperature – around 85-90 degrees Fahrenheit. Be aware that if your CO2 levels are too high for the amount of light or heat generated in the garden, you will see your plants become damaged from excess CO2.
Increasing CO2 concentrations will extend the temperature range in which RuBisCO may fix CO2 into sugar. With increased CO2 we see that as temperature increases, so does the rate of the chemical reaction that RuBisCO performs. This works because an increase in CO2 concentration means that the ratio of chemical substrates to products is being increased. If the CO2 concentrations are increased from ambient 300ppm to 1500ppm, the change in the ratio of reactants to products will allow plants to continue to fix CO2 into sucrose at leaf temperatures well above 27°C, all the way up to about 36°C! (see Figure 1)
RuBisCO is the plant enzyme responsible for the chemical reaction that is the first step of carbon fixation. This chemical reaction is seen as the conversion of CO2 and water into simple sugars during photosynthesis. The chemical reaction that RuBisCO performs is temperature-dependent.
Temperature Requirements for Photosynthesis
“New and experienced growers that want to reap the benefits of an LED strategy should familiarize themselves with the relationships between environmental factors that affect the efficiency of photosynthesis; leaf temperature, humidity, carbon dioxide concentration, and light intensity. In this article, we’ll discuss the effect of temperature on photosynthetic rate; how temperature and CO2 concentration are intimately linked to plant growth at higher temperatures; and compare the differences between ambient temperatures in HPS and LED grow rooms,” explains Dr. Matt Wheatley.
Fortunately, an indoor grower can adjust their environment to achieve optimal growing conditions. Controlled environments allow growers to maintain optimal temperatures, carbon dioxide concentrations, light intensity and relative humidity. So, let’s explore how a grower can adjust the growing environment to take advantage of high rates of growth that occur at high temperatures.
Leaf Temperature vs. Ambient Room Temperature
Based on scientific study and experimentation, Cannabis Consultant Dr. Matt Wheatley has found that an increase in the ambient room temperature of 5-7°C in LED-lit rooms relative to temperatures in HPS grow rooms is necessary to achieve similar internal leaf temperatures and plant growth rates as those experienced by plants in HPS-lit rooms. Keep in mind that as the ambient room temperature increases, the relative humidity decreases, and proportionate adjustments should be made to the relative humidity to adjust your vapor pressure deficits.