Abstract
Light-emitting diodes (LEDs) can be used as an energy efficient alternative to high-pressure sodium (HPS), which have historically been the standard for supplemental lighting in cannabis cultivation. However, there is a lack of scientific understanding in the cannabis industry regarding plant physiology, which has resulted in the adoption of cannabis cultivation methods based on hearsay rather than scientific research. The goals of this study were to 1) compare LED lighting options that are commonly used in the cannabis industry and 2) compare the top performing LED light with an industry standard HPS light. Specifically, three LED lights were compared (California Light Works ((SolarSystem 1100), BIOS Lighting (Icarus Gi2), and Fluence Bioengineering (now Fluence by Osram) (SPYDR xPLUS)), based on light distribution, leaf temperature, and photosynthetic performance indices. The LED versus HPS comparison was based on light response curves measured at photosynthetic photon flux densities (PPFD) of (0, 100, 200, 300, 400, 500, 750, 1000, 1250, 1500, 1750 and 2000 μmol∙m−2∙s−1), carbon assimilation rates (A) μmol CO2 m−2∙s−1 using a LiCor-6800 and resulting cannabinoid potency (THCA). The SPYDR xPLUS-Fluence by Osram had the highest performing LED light used in the LED comparison. At the suggested distance from bulb to canopy in the HPS versus LED comparison (6 inches for LEDs and 4 ft for HPS), carbon assimilation rates displayed a 142% percent increase in plants grown under LED vs. HPS with average photon flux densities of 795 and 298 μmol∙m−2∙s−1 for LED and HPS, respectively. All cultivars of Cannabis sativa L. showed increased cannabinoid potency when grown under LED illumination. The results of this study provide further insight regarding the selection of supplemental light to achieve maximum productivity of Cannabis sativa L.
Highlights
Light provides the energy required for photosynthesis and photosynthetic rate per unit leaf area is the driving force for all plant growth [1]
The light-emitting diodes (LED) versus HPS comparison was based on light response curves measured at photosynthetic photon flux densities (PPFD) of (0, 100, 200, 300, 400, 500, 750, 1000, 1250, 1500, 1750 and 2000 μmol∙m−2∙s−1), carbon assimilation rates (A) μmol CO2 m−2∙s−1 using a LiCor-6800 and resulting cannabinoid potency (THCA)
Given the superiority of consistency of the Fluence SPYDR xPLUS relative to the other LED lights tested, the SPYDR xPLUS was utilized for comparison to HPS lighting
Summary
Light provides the energy required for photosynthesis and photosynthetic rate per unit leaf area is the driving force for all plant growth [1]. Many horticultural crops are produced year-round, which requires the use of supplemental light. Among these crops is a burgeoning global cannabis market, which is projected to reach $103.9 billion by 2024 [5]. Cannabis cultivators have many lighting options to choose from. Among those options is newer light technology as found in light-emitting diodes (LED) and the more traditional high-intensity discharge (HID) lights (i.e. high-pressure sodium (HPS) and/or metal halide). The cannabis industry and C. sativa research have yet to provide the needed published peer reviewed results and data showing how C. sativa performs when grown using LED vs HPS illumination
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