Striving to Survive: Essential Oils, Glandular Trichomes & the Secondary Metabolism
Have you ever wondered how and why cannabis and other plants produce those amazing compounds that essential oils are derived from? It all has to do with glandular trichomes—tiny, specialized, hair-like formations found on plant stems and leaves.
Essential oils extracted from cannabis, as well as from herbs like mint and thyme, and from countless other plants, are key ingredients in products such as medicines, fragrances, and flavorings.
Demand for these products has been the driving force behind countless research studies conducted with the goal of understanding how and why plants produce these chemical compounds, and how growers can enhance their production. The research begins with the glandular trichome.
Glandular trichomes are tiny, specialized, hair-like formations found on the epidermis of plant stems and leaves. They are the evolutionary byproducts of plants striving to survive in tough environment. Though humans use them for their beneficial medicinal properties, we also enjoy their delicious flavors and amazing aromas.
At the tip of the hairs are glandular cells that produce, store and eventually secrete exudates such as resins and oils. Nearly all plant species produce some sort of hair-like formation, but only about 30% of vascular plants have the ability to create these sought-after substances.
Glandular trichomes come in several different shapes that are highly species-specific, to the point where they are often a characteristic used in the classification and identification of a plant species.
In cannabis plants, the glandular trichomes produced on the older fan leaves or stems are smaller and cling tight to the leave. As the plant develops, the glandular trichomes on the vegetation surrounding the flowers begin to grow longer and give the bud a crystalized or powdered look.
This is when the glandular trichomes are at peak production of exudates like THC and CBD. Other types of glandular trichome exudates include terpenoids, phenylpropenes, flavonoids and methyl ketones. Variations in the levels and types of these are what give different individual strains of cannabis their unique tastes, aromas and potencies.
The Secondary Metabolism
Glandular trichomes are not directly connected to a plant’s vascular system and therefore are not products of a plant’s primary metabolism. Primary metabolites—products of the primary metabolism—are compounds that play an important role in the basic life functions that allow plants to properly complete their full growth cycle, such as respiration, reproduction, cell division and growth.
Secondary metabolite compounds, such as the exudates found in glandular trichomes, are not directly involved in these essential functions, but are still believed to play a major role in a plant’s ability to adapt to the dangers of their environment. In nature, these compounds provide a level of defense against possible antagonists with antifungal, antibiotic, and antiviral properties.
These properties are the reason these compounds are sought after for medicinal purposes. This is especially true in the case of cannabis, which can have both physiological and psychological benefits. Not only do secondary metabolites help protect plants from microscopic assailants, they also help protect them from various insects and animals.
This is because some of the compounds secreted can cause severe discomfort when ingested. In addition, they also contain UV-ray-absorbing compounds that protect the leaves from potential harm from sunlight.
For years, scientists and growers alike have been working on ways to increase glandular trichome production in an effort to create and collect as much of the desired compounds from one plant as physically possible.
Since glandular trichomes are the result of a plant’s protective measure against environmental dangers, the question is, “How do we simulate a stressful situation in nature to enhance the production of these secondary metabolites on our plants at home, without causing them harm?”
Simulating a Stressful Situation
A plant’s glandular trichome production potential is the result of genetics developed through interactions with the surrounding environment. Plants that evolved in a more threatening environment generally have a higher level of glandular trichome production. But through certain stimuli, production levels can be increased in the home garden.
There are ways several to cause physical stress to a plant without greatly harming the growth cycle. For example, older leaves and branches can be cut to make the plant think it is under attack. Growers can also supplement with artificial UVA or UVB lighting in an effort to simulate some environmental stressors.
In nature, UV radiation from the sun can reduce the rate of photosynthesis in the leaves. The glandular trichomes produced by the plant help protect it from different types of UV radiation. Supplementing UV indoors during the flowering cycle should, theoretically, have the same effect, resulting in greater glandular trichome production.
There are several products that are marketed as having the ability to enhance glandular trichome production. I have used a few on my garden with satisfactory results, but just by looking at the product labels, it is hard to pinpoint the active ingredient or ingredients that provide such results.
Studies show the naturally occurring plant hormone jasmonate plays an important role in triggering the pathways that create secondary metabolites, and scientist have figured out how to create a synthetic version of the hormone, called jasmonic acid. However, growers need to show due diligence and research any possible harms when considering using a growth-regulating hormone of any kind, especially if the plant is intended for eventual human consumption.