Our olfactory sense is hardwired to our immune system. If a fragrance produced by a strain is particularity pleasing, there might be a reason. Fragrance can be a means for identifying strains for medical application, not just recreation. When we’re sick with a cold, we identify certain fragrances, like lemon, for example, to bring us relief. We evolved with this plant to ultimately be able to incorporate the plant cannabinoid compounds in our endocannabinoid receptor system.

Cannabinoids (CBD) interact with the body’s organs, nerves, and CB1, 2, and 3 receptor sites in the brain to mitigate conditions of pain and anxiety and establish a means for the terpenes to get into cells to perform medical functions far greater than sedation or elation, like slowing cancer cells. It’s not the CBD that attacks cancer — the CBD opens the cells in a tumor for terpenes to get inside cells to end replication in cancer cells without poisoning the body. With growth halted, the tumor may die.

This is why terpenes are more important than previously thought. It has been proven that terpenes can get inside different types of cancer to stop replication.

Cannabinoid ratios differ greatly in the various strains of weed and are associated with the production of terpenes. High-CBD strains produce high levels of myrcene as CBD synthase converts cannabigerol (CBG) into CBD and the associated terpenes. High-THC strains produce large levels of lemonene and pinene as the THC synthase converts tetrahydrocannabinolic acid (THC-A) into THC, tetrahydrocannabivarin (THC-V), and cannabichromine (CBC).

THC Terpenes Rely on Minerals and UV-B

These terpenes are mineral dependent for their production in trichomes, so let’s discuss the metal ions necessary for terpene production along with the light frequencies involved for synthesis, as well as those involved with terpene emittance and storage in flowering cannabis. Yes, that’s right, something many growers are not aware of is that the final fragrance of weed can be made stronger in the last 72 hours before harvest and curing.

Ultraviolet-B is required during flowering phase to stimulate genetic plastids in the trichome disc cells to create enzymes required for terpenes and cannabinoid synthesis.

But there are other photosynthetic processes in the phytochromes that can be employed to mediate light/dark signaling that increase terpene content and production.

First off, several metal ions are necessary since most terpene cyclases require a divalent ion such as magnesium (Mg2+) or manganese (Mn2+) for the cyclization of substrates. They are also necessary for THC-A conversion to THC by THC synthase. Moreover, all terpene cyclases, including limonene synthase, require either Mg2+ or Mn2+.

To explain the roles of Mg2+ and Mn2+ in terpene cyclization, it has been proposed that these metal ions might neutralize the negative charge of the diphosphate moiety and assist in ionization of the allylic diphosphate substrate to create the geranyl diphosphate terpene precursor molecule.

What is clear, however, is that divalent metal ions Fe (iron) and Mn (manganese) have been shown clearly in dispensary bud tests to affect levels of THC and CBD because deficiencies of Mn2+ (for THC) and Fe2+ (for CBD) in fertilizers during growth directly affect synthesis of THC and CBD.

Red Light and Terpene Potency

As shown earlier, CBD and THC levels are strongly related to mycrene and lemonene production. Everything is tied to adequate micronutrient minerals and specific light frequencies to form cannabinoids and terpenes. However, some frequencies that are eliminated at the end of growth can produce very strong terpene potency and subsequent highly fragrant dried buds.

Several light-sensitive photoreceptors outside the trichomes are involved in the processes of production and emission of terpenes, and different trichomes are dependent upon specific wavelengths of light to be activated or deactivated. Emission of terpenes is a process that is entirely dependent upon phytochromes and red and far-red light cues in most plant species. This is especially useful for growers using LED systems because it has been proven that if red LED light is eliminated during the last 72 hours of growth and only white and blue LEDs are used, the plant continues to synthesize terpenes, but a lack of red light to trigger the phytochrome results in a lack of terpene emission by the plant. This causes the terpenes to accumulate in the maturing trichomes.

The good news is that eliminating red light at the end of a flowering cycle has almost no effect on the final cannabinoid content of dried and cured buds. For stronger fragrance, medical potency, and higher commercial value of your buds, cut out red light 72 hours prior to harvest.