Uniformity and consistency are the top priorities every medical cannabis grower strives for. Yet, product uniformity has been one of the biggest issues of the industry since its inception. This has been mainly because research on best cannabis cultivation practices has been lagging behind immensely over the past decades due to oppressive prohibitionist policies. It is not a surprise that publications exploring the intricacies of this plant have taken quite a momentum since the industry got regulated in many countries around the world. Nirit Bernstein is an academic with the Institute of Soil Water and Environmental Sciences, and she has published many papers – even more so recently – that dive deep into the complexities of the cannabis plant. In her recent research published on Industrial Crops and Products, Bernstein and Danziger looked into how plant architecture manipulation can increase cannabinoid standardization specifically for medical cannabis.
As the authors point out, the genetic background of a given variety is known to be influenced by its chemical profile, as well as environmental factors and “morpho-spatial position in the plant’. With their study, they suggest that “spatial-position effects could be targeted by controlling plant architecture, for production of inflorescences of similar morpho-spatial characteristics.”
There are some plant architecture techniques that growers use nowadays, such as pruning, defoliation, branch removals, trellising, and so on. Yet, the results of defoliation techniques, for instance, are more based on anecdotal evidence than grounded in science. This is a bit of an issue, to say the least, for an industry where product consistency and uniformity are of the utmost importance. Thus, Danziger and Bernstein conducted a study to “identify architectural manipulation treatments suitable for minimizing variability in the cannabinoid profile throughout the plant.”
Experiment and first results
To study that, the authors examined eight plant architecture modulation treatments, such as defoliation or topping, and how these affect the cannabinoid profile as well as its spatial standardization in the plant. They used two cultivars approved for medical products and set up their control to see how different techniques affected them.
The first thing that they noticed was that the visual appearance of the plants was very much different between the different treatments. For instance, the defoliated plants appeared less dense. On the other hand, the plants of the bottom branches and leaf removal, and the bottom branches and leaf removal + defoliation treatments showed “secondary branching starting above the bottom 1/3 of the plants; both branch removals treatments and reduced branching, and both pruning treatments showed stimulated branching and a wider shoot.”
With regards to the cannabinoid content, the first and second branch removal treatments reduced the concentrations of cannabinoids compared to the control. However, “interestingly, the defoliation treatments increased CBDVA levels, while all other treatments reduced CBDVA by 6-23%. All treatments […] increased THCA concentrations.” At the same time, an important finding of the researchers was that plant average concentration of cannabinoids is not uniform throughout the plant. “The difference in the extent of change in concentration between the plant average and the apical inflorescence for different treatments suggests treatment effect on the degree of standardization.”
Indeed, the results showed the effects of the treatment on the chemical standardization in the plant. For instance, in one cultivar the uniformity of CBGA was way lower in the control and branch removal if compared to five other treatments.
Thus, one of the findings of this study is that “under conventional growing conditions, the grower will produce a medical cannabis plant product that contains a very large chemical variability,” they say. Bernstein and Danziger have demonstrated that some treatments do affect the chemical uniformity of a plant. Yet, there is still a lot to fully understand. “The level of standardization of most cannabinoids in the plants was increased by the treatments by raising the concentrations at the lower parts of the plant where concentrations are naturally considerably lower than at the plant top. The treatments that increased the most the concentrations of the lower inflorescences thus increasing standardization were ‘Double prune’, and the removal of bottom branches and leaves. The architecture modulation treatments elicited cultivar-specific effects on the cannabinoid profile. The treatment-induced changes in cannabinoid concentrations albeit statistically significant, were small, and although reduced the spatial variability in the plant, did not completely overcome it,” they conclude.