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Environmental factors on yield and cannabinoid production

In our previous article with Delphy, we talked about the influence of crop management practices on yield and cannabinoid production. Crop management practices such as pruning influence the plant directly and its surrounding environment, which in turn will affect the end product. Environmental factors such as temperature, CO2, and light all influence the growth and development of the plant, and by controlling these factors, it becomes possible to steer production towards the desired outcome, within the limits of the genotype, of course. In this article, Delphy will go a little more in-depth into the effects of environmental factors on flower yield and cannabinoid production in protected cultivation.

Each plant species has a basal temperature below which it cannot grow or develop. When temperatures rise above the base temperature, the rate of growth and development increases until an optimum temperature is reached. When temperature rises above the optimum, plant development slows down. The cannabis plant is no exception. To get the most out of your cannabis plants, it is important to keep the temperature at optimum levels during cultivation. Finding the right temperature for optimum development can be tricky as this can differ for each cultivar but generally speaking, the temperature should be between 22 to 26°C. However, plant growth and development are not dependent on just one factor. The optimum temperature for photosynthesis and development depends on the light intensity, as well as the CO2 concentration in the cultivation environment. While increasing temperature to the high end of the range to speed up development, you must make sure you are supplying sufficient light intensity (>600 µmol/m2/s1) and CO2 (400 to 800 ppm), or you risk decreasing net photosynthesis since your plants consume more assimilates than they produce. The developmental stage of the plant should also be taken into consideration, as each stage has a different optimum range.

When it comes to temperature and its influence on cannabinoid production, relatively little is known. To date, there are only a few scientific studies on the influence of temperature on cannabinoid production with conflicting results. While some studies show that higher temperatures can increase cannabinoid content, others studies show the exact opposite. Certainly, cannabinoid production can be influenced by temperature, but the response differs depending on the genotype and other environmental conditions. Before trying to use temperature as a strategy to increase cannabinoid production, more research needs to be done on this topic. This highlights the importance of applied research. By comparing the reactions of plants at varying temperatures in terms of flower yield and cannabinoid yield, new insights can be gained.

CO2 concentration
In regards to CO2 supplementation in cannabis cultivation, there is the potential to improve flower yield. At ambient CO2 levels (approximately 400 ppm), photosynthetic activity will be limited by CO2 availability. By supplying CO2 into a controlled environment, it is possible to increase photosynthetic activity by up to 50%. In general, CO2 levels between 400-800 ppm during the vegetative phase and 800-1000 ppm during the flowering stage are recommended. However, this must be accompanied by the high light intensity in order not to restrict photosynthetic activity, or else most of the supplemented CO2 is wasted. Furthermore, higher CO2 levels do not necessarily reflect an increase in flower yield. The source-sink balance is more important in determining if this sort of management increases yield because photoassimilates can be used to produce roots, stems, or leaves instead of flowers and cannabinoids. As for the influence of CO2 on cannabinoid production, we know from studies conducted on peppers and strawberries that CO2 levels can influence secondary metabolite production in these plant species. However, this hypothesis for cannabis plants still needs to be tested. It is important to realize that plant growth and yield, be it flowers or secondary metabolites, are dependent on an interplay between various environmental factors. Ultimately, it's about finding the right balance between these factors to ensure optimum growth throughout the cultivation, in which a low CO2 concentration can be the limiting factor.

Cannabis productivity and quality are greatly influenced by light intensity, quality, source, and photoperiod. Through photosynthesis, plant growth and development can occur, with light being its primary driver. The net photosynthesis rate will increase with increased light intensity until the light saturation point is reached (when CO2 or temperature becomes the limiting factor). In commercial cannabis cultivation, it is quite common to cultivate under high light intensities of up to 1000 to 1500 µmol m2/s1. However, it is important to keep a balance between light intensity, temperature, and CO2 concentration in the growth environment to ensure optimal growth is achieved. This interplay of different factors can make it difficult to find the right balance, especially since this differs for each cultivar.

Delphy consultancy and research
The takeaway message is this: The optimum growth and development of the plant depend on achieving a balance between the various environmental factors that affect the plant. The right balance depends on the cultivar and its developmental stage. "A" Delphy, our experts can give advice and training (on location or online) to help you ensure you achieve the optimum balance throughout your cultivation." "n addition, Delphy will be giving a Cannabis Cultivation Training in January 2023.

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