Optimizing Photoperiod Switch to Maximize Floral Biomass and Cannabinoid Yield in Cannabis sativa L.: A Meta-Analytic Quantile Regression Approach

Abstract

Cannabis sativa L. is an annual, short-day plant, such that long-day lighting promotes vegetative growth while short-day lighting induces flowering. To date, there has been no substantial investigation on how the switch between these photoperiods influences yield of C. sativa despite the tight correlation that plant size and floral biomass have with the timing of photoperiod switches in indoor growing facilities worldwide. Moreover, there are only casual predictions around how the timing of the photoperiodic switch may affect the production of secondary metabolites, like cannabinoids. Here we use a meta-analytic approach to determine when growers should switch photoperiods to optimize C. sativa floral biomass and cannabinoid content. To this end, we searched through ISI Web of Science for peer-reviewed publications of C. sativa that reported experimental photoperiod durations and results containing cannabinoid concentrations and/or floral biomass, then from 26 studies, we estimated the relationship between photoperiod and yield using quantile regression. Floral biomass was maximized when the long daylength photoperiod was minimized (i.e., 14 days), while THC and CBD potency was maximized under long day length photoperiod for ~42 and 49–50 days, respectively. Our work reveals a yield trade-off in C. sativa between cannabinoid concentration and floral biomass where more time spent under long-day lighting maximizes cannabinoid content and less time spent under long-day lighting maximizes floral biomass. Growers should carefully consider the length of long-day lighting exposure as it can be used as a tool to maximize desired yield outcomes.

Cannabis sativa L.: Crop Management and Abiotic Factors That Affect Phytocannabinoid Production

“…Finally, in addition to light quality and intensity, photoperiod can influence flower and phytocannabinoid yields (Table 1) [67,87]. The number of days a plant remains under a long photoperiod influences the size and number of flowers, as well as phytocannabinoid yield [41,102,103]. There is a lack of scientific information to determine the number of days a plant should spend in long-day lighting to maximize yield [102].…”

“…The number of days a plant remains under a long photoperiod influences the size and number of flowers, as well as phytocannabinoid yield [41,102,103]. There is a lack of scientific information to determine the number of days a plant should spend in long-day lighting to maximize yield [102]. According to a meta-analysis carried out by Dang et al (2022) [102], the increases in floral biomass and phytocannabinoid productivity responded differently according to the duration of the vegetative phase (long photoperiod).…”

“…There is a lack of scientific information to determine the number of days a plant should spend in long-day lighting to maximize yield [102]. According to a meta-analysis carried out by Dang et al (2022) [102], the increases in floral biomass and phytocannabinoid productivity responded differently according to the duration of the vegetative phase (long photoperiod). Floral productivity and the duration of the vegetative phase showed a negative linear relationship, suggesting that shorter vegetative growth periods are preferable to increase flower productivity.…”

“…Floral productivity and the duration of the vegetative phase showed a negative linear relationship, suggesting that shorter vegetative growth periods are preferable to increase flower productivity. In contrast, THC and CBD showed a negative quadratic relationship with long day length durations, suggesting that intermediate periods of vegetative growth maximize phytocannabinoid concentrations [102]. This information is important because it can be used to define management methods, such as ScroG and SoG techniques, depending on the purpose of the crop (flower or phytocannabinoid).…”

Morphological and yield responses of Cannabis sp. to night-time disruption.

“…The most studied commercial trait of the plant is the accumulation of cannabinoids in female inflorescences (Aliferis & Bernard-Perron, 2020; Stack et al , 2021; Dang et al , 2022). One of the particularities of cannabis lies in the photoperiod-dependent formation of inflorescences, but not floral induction (Spitzer-Rimon et al , 2019).…”