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Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment. (Canada) (full – 2021) Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment
Since the recent legalization of medical and recreational use of cannabis (Cannabis sativa) in many regions worldwide, there has been high demand for research to improve yield and quality. With the paucity of scientific literature on the topic, this study investigated the relationships between light intensity (LI) and photosynthesis, inflorescence yield, and inflorescence quality of cannabis grown in an indoor environment.
After growing vegetatively for 2 weeks under a canopy-level photosynthetic photon flux density (PPFD) of ≈425 μmol·m−2·s−1 and an 18-h light/6-h dark photoperiod, plants were grown for 12 weeks in a 12-h light/12-h dark “flowering” photoperiod under canopy-level PPFDs ranging from 120 to 1,800 μmol·m−2·s−1 provided by light emitting diodes. Leaf light response curves varied both with localized (i.e., leaf-level) PPFD and temporally, throughout the flowering cycle. Therefore, it was concluded that the leaf light response is not a reliable predictor of whole-plant responses to LI, particularly crop yield. This may be especially evident given that dry inflorescence yield increased linearly with increasing canopy-level PPFD up to 1,800 μmol·m−2·s−1, while leaf-level photosynthesis saturated well-below 1,800 μmol·m−2·s−1. The density of the apical inflorescence and harvest index also increased linearly with increasing LI, resulting in higher-quality marketable tissues and less superfluous tissue to dispose of.
There were no LI treatment effects on cannabinoid potency, while there were minor LI treatment effects on terpene potency. Commercial cannabis growers can use these light response models to determine the optimum LI for their production environment to achieve the best economic return; balancing input costs with the commercial value of their cannabis products.
Future research should expand to multiple cultivars of both indica- and sativa-dominant biotypes. Further, since plant yield responses to elevated CO2 can mirror the responses to elevated LI, the combined effects of CO2 and LI should be investigated on cannabis yield with an in-depth cost-benefit analysis of the optimum combination of these two input parameters.
www.frontiersin.org
Since the recent legalization of medical and recreational use of cannabis (Cannabis sativa) in many regions worldwide, there has been high demand for research to improve yield and quality. With the paucity of scientific literature on the topic, this study investigated the relationships between light intensity (LI) and photosynthesis, inflorescence yield, and inflorescence quality of cannabis grown in an indoor environment.
After growing vegetatively for 2 weeks under a canopy-level photosynthetic photon flux density (PPFD) of ≈425 μmol·m−2·s−1 and an 18-h light/6-h dark photoperiod, plants were grown for 12 weeks in a 12-h light/12-h dark “flowering” photoperiod under canopy-level PPFDs ranging from 120 to 1,800 μmol·m−2·s−1 provided by light emitting diodes. Leaf light response curves varied both with localized (i.e., leaf-level) PPFD and temporally, throughout the flowering cycle. Therefore, it was concluded that the leaf light response is not a reliable predictor of whole-plant responses to LI, particularly crop yield. This may be especially evident given that dry inflorescence yield increased linearly with increasing canopy-level PPFD up to 1,800 μmol·m−2·s−1, while leaf-level photosynthesis saturated well-below 1,800 μmol·m−2·s−1. The density of the apical inflorescence and harvest index also increased linearly with increasing LI, resulting in higher-quality marketable tissues and less superfluous tissue to dispose of.
There were no LI treatment effects on cannabinoid potency, while there were minor LI treatment effects on terpene potency. Commercial cannabis growers can use these light response models to determine the optimum LI for their production environment to achieve the best economic return; balancing input costs with the commercial value of their cannabis products.
Conclusions
We have shown an immense plasticity for cannabis to respond to increasing LI; in terms of morphology, physiology (over time), and yield. The temporal dynamics in cannabis leaf acclimations to LI have also been explored, addressing some knowledge-gaps in relating cannabis photosynthesis to yield. The results also indicate that the relationship between LI and cannabis yield does not saturate within the practical limits of LI used in indoor production. Increasing LI also increased harvest index and the size and density of the apical inflorescence; both markers for increasing quality. However, there were no and minor LI treatment effects on potency of cannabinoids and terpenes, respectively. This means that growers may be able to vastly increase yields by increasing LI but maintain a relatively consistent secondary metabolite profile in their marketable products. Ultimately, the selection of the economic optimum canopy-level LI for a given commercial production system depends on many interrelated factors.
We have shown an immense plasticity for cannabis to respond to increasing LI; in terms of morphology, physiology (over time), and yield. The temporal dynamics in cannabis leaf acclimations to LI have also been explored, addressing some knowledge-gaps in relating cannabis photosynthesis to yield. The results also indicate that the relationship between LI and cannabis yield does not saturate within the practical limits of LI used in indoor production. Increasing LI also increased harvest index and the size and density of the apical inflorescence; both markers for increasing quality. However, there were no and minor LI treatment effects on potency of cannabinoids and terpenes, respectively. This means that growers may be able to vastly increase yields by increasing LI but maintain a relatively consistent secondary metabolite profile in their marketable products. Ultimately, the selection of the economic optimum canopy-level LI for a given commercial production system depends on many interrelated factors.
Future research should expand to multiple cultivars of both indica- and sativa-dominant biotypes. Further, since plant yield responses to elevated CO2 can mirror the responses to elevated LI, the combined effects of CO2 and LI should be investigated on cannabis yield with an in-depth cost-benefit analysis of the optimum combination of these two input parameters.
Frontiers | Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment
Since the recent legalization of medical and recreational use of cannabis (Cannabis sativa) in many regions worldwide, there has been high demand for researc...
www.frontiersin.org
