From physics to fixtures to food: current and potential LED efficacy

Kusuma, Paul; Pattison, P. Morgan; Bugbee, Bruce

doi:10.1038/s41438-020-0283-7

Cited by 171 publications

(164 citation statements)

References 46 publications

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“…Far-red supplementation comes with an energy cost and it remains unclear whether it is cost effective to add far-red photons or to increase the traditionally defined photosynthetic photons (400 to 700 nm) by the same amount. Far-red photons contain lower energy and thus can be generated with higher efficacy (moles of photons per unit of electric energy) than red, blue, and green photons using current LED technology ( Kusuma et al, 2020 ). Recent research on the photosynthetic effect of far-red photons has provided compelling evidence that far-red photons (700–750 nm) significantly increase leaf and canopy photosynthesis when added to photons within 400 to 700 nm ( Zhen and Bugbee, 2020 and citations therein).…”

Section: Discussionmentioning

confidence: 99%

“…Because crop productivity exhibits a strong linear correlation with radiation intercepted by canopies ( Monteith, 1977 ; Gifford et al, 1984 ; Beadle and Long, 1985 ), increased leaf expansion and accelerated canopy closure are desirable traits, especially in annual crops. Recent advances in light emitting diode (LED) technology enable precise control of spectral quality in controlled environment crop production ( Massa et al, 2008 ; Kusuma et al, 2020 ). Perhaps the most powerful effect is the simulation of shade through FR supplementation, often without reducing light intensity in the PAR region.…”

Section: Introductionmentioning

confidence: 99%

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Substituting Far-Red for Traditionally Defined Photosynthetic Photons Results in Equal Canopy Quantum Yield for CO2 Fixation and Increased Photon Capture During Long-Term Studies: Implications for Re-Defining PAR

Zhen

Bugbee

2020

Front. Plant Sci.

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Far-red photons regulate shade avoidance responses and can have powerful effects on plant morphology and radiation capture. Recent studies have shown that far-red photons (700 to 750 nm) efficiently drive photosynthesis when added to traditionally defined photosynthetic photons (400-700 nm). But the long-term effects of far-red photons on canopy quantum yield have not yet been determined. We grew lettuce in a four-chamber, steady-state canopy gas-exchange system to separately quantify canopy photon capture, quantum yield for CO 2 fixation, and carbon use efficiency. These measurements facilitate a mechanistic understanding of the effect of far-red photons on the components of plant growth. Daytime photosynthesis and night-time respiration of lettuce canopies were continuously monitored from seedling to harvest in five replicate studies. Plants were grown under a background of either red/blue or white light, each background with or without 15% (50 mmol m −2 s −1) of far-red photons substituting for photons between 400 and 700 nm. All four treatments contained 31.5% blue photons, and an equal total photon flux from 400 to 750 nm of 350 mmol m −2 s −1. Both treatments with far-red photons had higher canopy photon capture, increased daily carbon gain (net photosynthesis minus respiration at night), and 29 to 31% more biomass than control treatments. Canopy quantum yield was similar among treatments (0.057 ± 0.002 mol of CO 2 fixed in gross photosynthesis per mole of absorbed photons integrated over 400 to 750 nm). Carbon use efficiency (daily carbon gain/gross photosynthesis) was also similar for mature plants (0.61 ± 0.02). Photosynthesis increased linearly with increasing photon capture and had a common slope among all four treatments, which demonstrates that the faster growth with far-red photon substitution was caused by enhanced photon capture through increased leaf expansion. The equivalent canopy quantum yield among

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Substituting Far-Red for Traditionally Defined Photosynthetic Photons Results in Equal Canopy Quantum Yield for CO2 Fixation and Increased Photon Capture During Long-Term Studies: Implications for Re-Defining PAR

Zhen

Bugbee

2020

Front. Plant Sci.

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“…HPS cannot be used in mediterranean greenhouse cultivation because the daily temperature is higher, and the height of greenhouses is lower than in northern regions. Recently, another SL (light-emitting diodes: LEDs) technology is being developed, which has higher efficiency than HPS lamps [7]. LEDs can produce high luminous flux with low radiant heat and maintain their light efficacy for years, while HPS lamps need to be replaced more frequently and consume a great deal of electrical power by generating alongside visible light [8].…”

Section: Introductionmentioning

confidence: 99%

Supplemental LED Increases Tomato Yield in Mediterranean Semi-Closed Greenhouse

Palmitessa

Paciello²,

Santamaria

2020

Agronomy

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Supplemental light (SL) is a technique used to increase horticulture yield, especially in northern countries, where the Daily Light Integral (DLI) is a limiting factor during fall and winter, and which could also be used to obtain higher tomato yield at the Mediterranean latitude. In this study, three tomato hybrid (F1) cultivars were grown for year-round production in a commercial semi-closed glasshouse in Southern Italy: two of the cherry fruit-type (‘Juanita’ and ‘Sorentyno’) and one mini plum fruit-type (‘Solarino’). From 120 to 243 days after transplant, light-emitting diode (LED) toplights were used as SL, with a photoperiod of 18 h. The main climatic parameters inside and outside the glasshouse were recorded, and tomato plants’ development and yield were examined. Plants grown with LEDs had longer stems as compared to control treatment (9.53 vs. 8.79 m), a higher stem thickness and yielded more trusses. On average, the yield was 21.7% higher with LEDs. ‘Sorentyno’ was the cultivar with the highest cumulated productivity when it was grown under SL. However, the cultivar with best light use efficiency under LEDs was ‘Solarino’. Therefore, supplemental LED from mid-December until March enhanced tomato growth and yield, opening a favorable scenario for large-scale application of this technology also in the Mediterranean area.

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“…Issues with these metrics are exacerbated under light-emitting diodes (LEDs), which are important to photobiology because of their narrow bandwidth. Furthermore, the high efficiency output of LEDs has made them a prominent addition to controlled environment agriculture (Kusuma et al, 2020). In these plant factories, plant morphology can be manipulated by the specific choice of LEDs, but first it is vital to develop proper metrics to predict responses.…”

mentioning

confidence: 99%

Far-red Fraction: An Improved Metric for Characterizing Phytochrome Effects on Morphology

Kusuma¹,

Bugbee²

2021

J. Amer. Soc. Hort. Sci.

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Phytochrome, a well-studied photoreceptor in plants, primarily absorbs in the red (R) and far-red (FR) regions and is responsible for the perception of shade and subsequent morphological responses. Experiments performed in controlled environments have widely used the R:FR ratio to simulate the natural environment and used phytochrome photoequilibrium (PPE) to simulate the activity of phytochrome. We review why PPE may be an unreliable metric, including differences in weighting factors, multiple phytochromes, nonphotochemical reversions, intermediates, variations in the total pool of phytochrome, and screening by other pigments. We suggest that environmental signals based on R and FR photon fluxes are a better predictor of plant shape than the more complex PPE model. However, the R:FR ratio is nonintuitive and can approach infinity under electric lights, which makes it difficult to extrapolate from studies in controlled environments to the field. Here we describe an improved metric: the FR fraction (FR/R+FR) with a range from 0 to 1. This is a more intuitive metric both under electric lights and in the field compared with other ratios because it is positively correlated with phytochrome-mediated morphological responses. We demonstrate the reliability of this new metric by reanalyzing previously published data.

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From physics to fixtures to food: current and potential LED efficacy

Cited by 171 publications

References 46 publications

Substituting Far-Red for Traditionally Defined Photosynthetic Photons Results in Equal Canopy Quantum Yield for CO2 Fixation and Increased Photon Capture During Long-Term Studies: Implications for Re-Defining PAR

Substituting Far-Red for Traditionally Defined Photosynthetic Photons Results in Equal Canopy Quantum Yield for CO2 Fixation and Increased Photon Capture During Long-Term Studies: Implications for Re-Defining PAR

Supplemental LED Increases Tomato Yield in Mediterranean Semi-Closed Greenhouse

Far-red Fraction: An Improved Metric for Characterizing Phytochrome Effects on Morphology

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