What Is UV Light?
At this point you might be asking, “how is UV light different from normal light?” Even though humans can’t see it, a good way to think of UV is to visualize a rainbow and pretend there is an extra color band past the blue and purple. All light is basically just waves of energy, and UV light is just like any other form of radiation. These waves wash over your plants at different frequencies (how many waves pass per second). UV light has a smaller gap between each wave than visible light, which means more waves are passing per second. This gives UV high energy, making it more like an X-ray than a radio wave.
How Does UV Light Effect Marijuana Plants?
But what does all this mean to your cannabis garden? To answer that, we need to investigate how UV light affects plants cells. Ultra-violet radiation, particularly UVB, has been shown to be detrimental to plant cell function. UV causes damage to plant cells in the same way it tears through your skin, eventually causing sunburn. As a result of this damage, all plants have created defenses against UV in the form of gene UVR8.
UVR8 is a protein molecule which senses UV all by itself, and then “tells” plant cells to change their behavior. Exactly how UVR8 molecules sense UV was recently discovered and is pretty interesting. UVR8 is what chemists call a “dimer.” which just means that it’s made of two structurally similar protein subunits. When UV light hits the two protein subunits in UVR8, their charge weakens and they break apart. To help visualize this, imagine rubbing two balloons against one another. The balloons will stick together because of a static charge. Now imagine the balloons get rained on. The water takes the static charge with it and the two balloons fly apart. In this example, the balloons are the two protein subunits and the rain is UV light cascading down on the plant cell. After the protein subunits break apart, they head to the cell nucleus to deliver their information.
More UV Can Mean More THC
One of these changes caused by this information is very important in your cannabis garden. UV stress stimulates cannabis’ production of chemicals via the phenylpropanoid pathway, specifically malonyl-CoA and phenylalanine. Why is this important? It’s important because cannabis uses malonyl-CoA to make Olivtol, which it in turn uses to make THC. Now we can see the specific pathway which cannabis uses to increase potency when exposed to UV light.
UV light is already present in your garden, but it’s being blocked by the special glass your bulb is made of. Lamp manufacturers must use this type of glass by law because UV light can cause skin cancer when humans are overexposed. You wouldn’t want everyone getting cancer from street lights would you? You can increase the amount of UV getting to your cannabis by mixing metal halide bulbs into your bloom room and leaving the glass off your air-cooled hoods. But a better and safer way is to buy and install cheap fluorescent UV lights.
Remember, UV light causes stress to the plant, so put the fluorescents on timers and only have them on for part of the light cycle. Having them on for fifteen minutes of every hour should do the trick. The only downside of this whole process is that yields go down slightly. The plant has to reroute resources and undergoes some physical damage from the UV. As long as you don’t overdo the UV the increase in quality is well worth the decrease in yield.
Safety Note: Never go into your room during UV exposure times, unless you manually turn the lights off! Overexposure to ultra-violet radiation can cause skin cancer in humans.