Ask the Doc: Photosynthesis and CO2



If you’ve ever taken a biology class you have probably had to memorize the equation for photosynthesis. Now photosynthesis is the most important metabolic pathway from plants because it provides them their energy so if you have a lower photosynthetic rate, your plants are just going to grow slower and you’ll get lower yields. So all growers should be maximizing their rate of photosynthesis. Now in order to maximize your rate of photosynthesis you want to make sure your plant has all the inputs to get the sugar they need. So the inputs for photosynthesis are water carbon dioxide and light. Now photosynthesis has a 2-step metabolic pathway: the first step is called the light reaction. In the light reaction there are proteins inside the chloroplast that they get energized with light energy and this then allows them to split the water molecule and they’re going to create what’s called chemical energy. They’re gonna make the molecules AGP and NADPH so this is chemical energy. Now the second step of photosynthesis is called the Calvin cycle. The Calvin cycle is what’s going to use the carbon dioxide. So the idea of adding more carbon dioxide to your growth room is to maximize the Calvin cycle, because that makes the sugar or glucose and this is the energy for plants. So imagine a powerlifter or an Olympic athlete. How much they consume in the day,to have these fantastic performances a lot and that’s the idea with photosynthesis. You want to maximize your rate of photosynthesis so your plants grow with their fastest rate and you get the yields. The thing to understand is that no matter how much co2 you give, if your plants don’t have the chemical energy they get from light, then the Calvin cycle can’t go any faster. So light is the limiting factor not co2. So you need to be having at least 700 ppfd in your grow areas. You need to be using a high wattage full-spectrum LED, a high pressure sodium bulb or a ceramic metal halide both with these type of lights you’re gonna have high light intensity which means when you add co2 you’re really gonna see some improvements in your plant growth. So if you’re looking to improve your growing the first thing you should be doing is increasing the amount of light. So get a high pressure sodium, ceramic metal halide or a high wattage full-spectrum LED. You’re gonna be maximizing your use of light and then when you add carbon dioxide you’re gonna get the full benefits of maximum growth maximum you.