Cannabis has become one of the most interesting plants for cultivation and pharmacology because of its medicinally useful cannabinoids and terpenoids.
They are predominantly concentrated in the glandular trichomes of female inflorescences and reportedly have therapeutic potential for treating chronic pain, nausea, spasticity of multiple sclerosis, anorexia, and also symptoms of Tourette’s syndrome.
This is very important since the consistency in producing these pharmacologically active compounds must prevail, and incorrectly grown flowers are often administered directly to patients.
This means that appropriate strict control of the environment in cannabis cultivation, especially for medical purposes, is critical to constancy in yield and concentration of specialized cannabinoids.
One major factor in controlled environment cultivation is lighting, which controls not only how plants grow and develop but also drives energy efficiency in cultivation.
A new paper explains how different light spectra can influence the growth, morphology, and metabolite accumulation of the medical cannabis plant by interacting with the red wavelengths in white light fractions.
Light Spectra and Cannabis Growth
The role of light spectra in the process of plant growth and metabolite production is well described.
However, because most studies were performed on common plants and not on medical cannabis, how the different spectra affect plants remains entirely unclear.
Literature has shown that red light—especially 640 nm and 660 nm wavelengths—strongly promotes photosynthesis and, subsequently, the growth of plants.
This is due to the fact that red light is most efficiently absorbed by chlorophyll a and b, two major photosynthetic green pigments.
In this study, the authors of this paper assessed how the light spectrum affects cannabis using white light with two red peaks at 640 and 660 nm versus only a single one at 660 nm.
The study aimed to determine which variation of the process affected plant morphology, photosynthesis, and the accumulation of plant-specialized metabolites under different light intensities.
Methods
This study was done on plants of the King Harmony variety, which were grown in intraclimate-controlled chambers.
They were further divided according to their different light treatments. Genetically identical mother plants were used to ensure consistency throughout the experiment.
The plants were grown for two growth cycles under different light spectra and intensities.
The variables considered in this study were the red wavelengths with peak values at 640 nm and 660 nm and white light fraction.
Plants were grown under low light intensity (600 μmol m^-2 s^-1) and high light intensity (1200 μmol m^-2 s^-1) to study the impact on their growth and cannabinoid production.
Results and Discussion
It was found that white light having two red peaks at 640 and 660 nm resulted in an higher weight of inflorescence than white light with a single red peak at 660 nm.
This perhaps explains why the distribution of light energy in both red wavelengths allows more efficient absorption and conversion of light energy for photosynthesis, hence promoting dry matter production in plants.
Interestingly, this increase in the weight of flowers was associated with an increase in total plant weight without any effect on dry matter partitioning to the flowers.
These findings suggest that while overall biomass production was high, biomass distribution to different parts of plants had not changed significantly.
It was further observed that while increasing the white light fraction improved dry matter partitioning to the flowers, it did not significantly affect total plant dry matter production.
This points to the need to optimize not only the intensity but also the spectrum of light for desirable growth outcomes in medical cannabis.
Regarding morphological analysis, increases in white fraction contributed to reduced plant height and, hence, its compact architecture. Such a structural change may improve the light distribution through the canopy, enhancing global photosynthesis and plant growth.
Implications for Medical Cannabis Growing
The findings of this research could have enormous implications for medical cannabis cultivation.
Light spectra optimization—particularly the ratio of red and white light—will go a long way in enhancing photosynthesis, which will increase yields and concentrate uniformity across different products of medicinal cannabis plants.
Also, the energy efficiency of lighting systems under controlled environment cultivation is critical.
It can therefore be said that using optimized light spectra for different plant species can decrease energy consumption while maintaining or even improving yield, which again means the cultivation process becomes more efficient.
This paper, therefore, speaks to the pivotal nature of light spectrum management in medicinal cannabis production.
One can adjust wavelength and light intensity for improved growth patterns, cannabinoid production, and other general efficiency savings in cannabis cultivation systems.
Continued efforts in researching the convoluted connections of light spectra with plant physiology will further refine cultivation practices for medical cannabis.
