The legalization and evolving regulations around the world regarding the cultivation of Cannabis sativa L. have led to a growing demand for optimized methods of mass propagation of cannabis plants. Micropropagation is a vital tool in this context, offering advantages such as rapid multiplication of elite clones, reduced space requirements, and clean plant material that minimizes the risks of diseases and pests. While micropropagation methods for cannabis have been developed through numerous studies, the effect of light on the success of micropropagation has been relatively understudied. Given that specially tailored LED lighting in cannabis production has proven to increase yield, cannabinoid content, and affect plant morphology in vivo, there is reason to believe that light intensity and spectra could have similar effects in vitro during tissue culture and micropropagation.
How is Micropropagation Done?
Micropropagation involves producing large quantities of clean, healthy clones free of viruses and diseases. In this process, plant tissue or organs are taken from a donor plant, and new tissue is grown and differentiated in an aseptic medium isolated from external factors. The growing medium contains sucrose, plant hormones, and macro- and micronutrients. Choosing the right combination of growth regulators and nutrients is crucial, alongside other factors such as the health and age of the donor plant. Methods are species-specific, and all stages can vary between species and cultivars.
Collaboration between University of Helsinki and Valoya Gives Insights on Best Lighting for Micropropagation
Valoya, in collaboration with the University of Helsinki, studied how light quality and intensity affect cannabis multiplication rate and rooting in vitro. Experiments were conducted with a hemp-type Cannabis sativa with high cannabidiol (CBD) and naturally low tetrahydrocannabinol (THC) concentrations (<0.2%). Three different Valoya spectra (NS12, AP67, and an AP67-NS12 combination) and three intensity levels (30, 70, and 170 μmol m-2 s-1) were compared.
Light intensity significantly affected shoot height, with the lowest intensity (30 μmol m-2 s-1) producing the tallest shoots. The highest number of plants that rooted, was found at the low intensity of 30 μmol m-2 s-1 with the AP67 spectrum. Although the most shoots were produced at the low intensity of 30 μmol m-2 s-1 and using the NS12 spectrum.
Conclusion
This study found the best results were achieved with Valoya’s AP67 and NS12 at 30 μmol m-2 s-1. There were some minor differences between better rooting (AP67) and better shoots (NS12) produced in the trial. Depending on the needs of the grower, they should also consider how the light looks to the human eye, for instance, white lights can also be better for the inspection of plantlets. With the optimal cultivar and refined micropropagation methods, these insights could greatly benefit the cannabis cultivation industry.
