Cannabis has been cultivated by humans for many centuries. Due to the prohibition of cannabis, many long-time cannabis growers had to operate undercover for fear of prosecution. This has in turn limited research on cannabis cultivation and the sharing and exchange of useful cultivation strategies and techniques.
Things are changing thankfully, now that the cannabis industry is legalizing and research on cultivation has become more popular. Cultivation ‘tips and tricks’ that have been handed down by generations of cultivators within the unregulated legacy industry are now being investigated by scientists to determine if they actually have merit.
One such technique is using pre-harvest mechanical stress, or ‘mechanical wounding,’ on cannabis plants. Cultivators have been using mechanical stress to improve the quality of their harvest for years. A recent study by the Volcani Institute focused on pre-harvest stress and its effect on cannabinoid and other terpenes. The findings of the study were published in a journal. BMC Plant Biology.
The traditional cannabis growers believe that mechanical-wounding stresses enhance the production of cannabinoids and therapeutic metabolites specific to cannabis. This common belief was not scientifically tested and lacked empirical validation. The present study tested the hypothesis that the stress of wounding stimulates the production of secondary metabolites in cannabis and can regulate its therapeutic chemical composition. The authors of the study wrote.
The study concentrated on two specific mechanical stress techniques. The first is ‘stem-splitting,’ in which cultivators slice the plant’s main stalk right before harvest. The second is ‘leaf-wounding,’ in which growers damage the plant’s fan leaves.
To evaluate this hypothesis we examined the impact of two wounding stress practices that are common to traditional cannabis cultivation: stem-splitting or leaf-wounding. We also looked at plant physiological function. Stress was applied pre-harvest at a time when secondary-metabolite production is intense. Two stem-splitting treatments were applied 7 and 11 days prior to harvest. Three leaf-wounding treatment treatments were also applied 7 and 11. The researchers said.
The hypothesis was supported by the results, which showed that mechanical stress stimulation stimulated cannabinoids and terpenes. Two major cannabinoids, THC and CBC were increased by leaf-wounding eleven days pre-harvest but not the other wounding treatments. This supports an interaction between injured organ and timing of injury. “Stem-splitting, 11-days-pre-harvest, increased concentrations in many sesquiterpenes. However, leaf-wounding impacted only a small number compounds, demonstrating organ-dependent responses.” Researchers determined.
The findings show that the effects of wounding and stress on cannabinoid, terpene, and individual compounds in each chemical group are dependent upon organ, timing, as well as the intensity of the stress. The different effects on cannabinoids and terpenes and the individual compounds within each chemical group suggests that mechanical damage impacts cannabinoid biosynthesis downstream of GPP (geranyl-diphosphate), at distinct regulatory points. The researchers concluded.
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