Growers of Medicinal Cannabis have known about using LED lighting for some time. A new study by the Wageningen University & Research Centre has shown that some varieties of cannabis plants grown under LED lighting may produce more of the plant’s medicinally active substances.
The study compared the content of active substances of the plants grown under LED lighting with grown under lighting that is just as intensive as using the conventional high-pressure sodium grow lights (known as SON-T lamps). The study also showed that medicinal cannabis can grow well under high lighting levels.
In the spring of 2016, experts in greenhouse technology at Wageningen University & Research Centre conducted the study that examined the influence of cultivation conditions on the growth and yield of medicinal cannabis. The study measured, among other plant characteristics and traits, the quantities of Cannabidiol (CBD) and Tetrahydrocannabinol (THC) produced.
Cannabidiol (CBD) can be used in the Netherlands to treat disorders such as Multiple Sclerosis. Additionally, THC can be used to combat and alleviate medical conditions such as Tourette syndrome and therapy-resistant glaucoma, and health complaints such as weight loss, nausea, and vomiting.
The study looked at the cultivation conditions under which medicinal cannabis plants best thrive. The horticulturists paid special attention to LED lighting. Few studies about the growth of Medicinal Cannabis in greenhouses have been done previously. So, the group of researchers also investigated other factors that might influence cultivation, such as moisture levels, temperature, plant nutrients, as well as the incidence of diseases and pests.
The study compared the use of high-pressure sodium (SON-T) lights and water cooled LED units.
They exposed the crops grown under LED lighting to two intensities of light. One intensity was equal to the SON-T lighting, and one that was significantly higher.
To simulate autumn growth conditions in the springtime when they conducted the greenhouse study, they covered the greenhouse with black-out cloth that would allow no more than 100 µmol s-1 cm-2 of light to enter the greenhouse.
All plants were given a long simulated day (in terms of light) for four weeks. Afterward, they exposed the plants to shorter simulated daylight hours until harvested. The plants grew profusely resulting in dense foliage.
However, thrips were found in the plants, which were kept in check using biological crop protection agents.
Humidity was high in the greenhouse environment of the densely foliated plants. The high humidity led to the development of fungus (Sclerotinia). Again, the horticulturists used no chemical agents to combat the fungus.
Photosynthesis was measured during the growth process. During the harvest, the cannabis plants’ length and weight (both fresh and dried) were measured. Specimens were taken of the various treatment methods and analyzed for their THC and CBD content after drying by a specialized laboratory.
The medicinal cannabis used in the study was found to be growable in greenhouses under LED lighting.
The cannabis varieties of this study were also found to withstand high light intensity levels (µmol s-1 cm-2).
Plants grown under the higher light intensity (400 µmol s-1 cm-2) were found to produce a higher bud weight in compared to the plants grown under the lower light intensity of 250 µmol s-1 cm-2.
The THC content was found to be higher in one cultivar (a study’s group of plants grown under the same test conditions); and lower in another.
In all varieties of medicinal cannabis tested, LED lighting produced a higher content of active substances than the high-pressure sodium (SON-T) lights with the same light intensity. However, plants grown under SON-T produced heavier clusters of buds than those grown under 250 µmol s-1 cm-2 LED.
In one group, they found a higher total weight in terms of the active substances produced. In plants grown under 400 µmols-1 cm-2 LED, they found that both the percentage and the nominal weight of the substances were higher than that measured in the plants grown under 250 µmols-1 cm-2 SON-T.
Study Funding and Permits
Lemnis Oreon, a developer and producer of LED lighting concepts and PB Techniek, a supplier of LED lighting systems and other products commissioned the study. The Dutch Ministry of Health, Welfare and Sport granted the necessary permits to allow the study to be conducted.