Westmoreland F Mitchell, Kusuma Paul, Bugbee Bruce
Crop Physiology Laboratory, Utah State University, Logan, Utah, United States of America.
PLoS One. 2021 Mar 23;16(3):e0248988. doi: 10.1371/journal.pone.0248988. eCollection 2021.
LED technology facilitates a range of spectral quality, which can be used to optimize photosynthesis, plant shape and secondary metabolism. We conducted three studies to investigate the effect of blue photon fraction on yield and quality of medical hemp. Conditions were varied among studies to evaluate potential interactions with environment, but all environmental conditions other than the blue photon fraction were maintained constant among the five-chambers in each study. The photosynthetic photon flux density (PPFD, 400 to 700 nm) was rigorously maintained at the set point among treatments in each study by raising the fixtures. The lowest fraction of blue photons was 4% from HPS, and increased to 9.8, 10.4, 16, and 20% from LEDs. There was a consistent, linear, 12% decrease in yield in each study as the fraction of blue photons increased from 4 to 20%. Dry flower yield ranged from 500 to 750 g m-2. This resulted in a photon conversion efficacy of 0.22 to 0.36 grams dry flower mass yield per mole of photons. Yield was higher at a PPFD of 900 than at 750 μmol m-2 s-1. There was no effect of spectral quality on CBD or THC concentration. CBD and THC were 8% and 0.3% at harvest in trials one and two, and 12% and 0.5% in trial three. The CBD/THC ratio was about 25 to 1 in all treatments and studies. The efficacy of the fixtures ranged from 1.7 (HPS) to 2.5 μmol per joule (white+red LED). Yield under the white+red LED fixture (10.4% blue) was 4.6% lower than the HPS on a per unit area basis, but was 27% higher on a per dollar of electricity basis. These findings suggest that fixture efficacy and initial cost of the fixture are more important for return on investment than spectral distribution at high photon flux.
LED技术可实现多种光谱质量，可用于优化光合作用、植物形态和次生代谢。我们进行了三项研究，以调查蓝光光子比例对医用大麻产量和品质的影响。研究之间的条件有所不同，以评估与环境的潜在相互作用，但在每项研究的五个试验箱中，除蓝光光子比例外的所有环境条件均保持恒定。通过升高灯具，在每项研究的各处理中，光合光子通量密度（PPFD，400至700纳米）严格维持在设定点。来自高压钠灯（HPS）的蓝光光子比例最低为4%，而来自LED的蓝光光子比例分别增加到9.8%、10.4%、16%和20%。在每项研究中，随着蓝光光子比例从4%增加到20%，产量持续线性下降12%。干花产量范围为500至750克/平方米。这导致每摩尔光子的光子转换效率为0.22至0.36克干花质量产量。在900的PPFD下产量高于750微摩尔/平方米·秒-1时的产量。光谱质量对CBD或THC浓度没有影响。在试验一和试验二中，收获时CBD和THC分别为8%和0.3%，在试验三中为12%和0.5%。在所有处理和研究中，CBD/THC比例约为25比1。灯具的效率范围为每焦耳1.7（HPS）至2.5微摩尔（白色+红色LED）。白色+红色LED灯具（蓝光10.4%）下的单位面积产量比HPS低4.6%，但每美元电费基础上的产量高27%。这些发现表明，对于高光子通量下的投资回报率而言，灯具效率和灯具初始成本比光谱分布更重要。
