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From physics to fixtures to food: current and potential LED efficacy
摘要： Light-emitting diodes (LEDs) have enabled a historic increase in the conversion of electric energy to photons, but this is approaching a physical limit. The theoretical maximum efficiency occurs when all input energy is converted to energy in photosynthetic photons. Blue LEDs can be 93% efficient, phosphor-converted “whites” 76% efficient, and red LEDs 81% efficient. These improvements open new opportunities for horticultural lighting. Here we review (1) fundamental physics and efficiency of LEDs, (2) the current efficacy of LEDs, (3) the effect of spectral quality on crop yield, and (4) the potential efficacy of horticultural fixtures. Advances in the conversion of photons to yield can be achieved by optimization of spectral effects on plant morphology, which vary among species. Conversely, spectral effects on photosynthesis are remarkably similar across species, but the photons conventional (400–700 nm) may need to be modified. The upper limit of LED fixture efficacy is determined by the LED package efficacy multiplied by four factors inherent to all fixtures: thermal droop, driver (power supply) current droop, inefficiencies, and optical losses. With current LED technology, the calculations indicate efficacy limits of 3.4 μmol J?1 for white + red fixtures, and 4.1 μmol J?1 for blue + red fixtures. Adding optical protection from water and high humidity reduces these values by ~10%. We describe tradeoffs between peak efficacy and cost.
关键词： spectral quality,fixture efficacy,horticultural lighting,LEDs,photosynthetic photons
更新于2025-09-19 17:13:59
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Alternating Red and Blue Light-Emitting Diodes Allows for Injury-Free Tomato Production With Continuous Lighting
摘要： Plant biomass is largely dictated by the total amount of light intercepted by the plant [daily light integral (DLI) — intensity × photoperiod]. Continuous light (CL, 24 h lighting) has been hypothesized to increase plant biomass and yield if CL does not cause any injury. However, lighting longer than 18 h causes leaf injury in tomato characterized by interveinal chlorosis and yield is no longer increased with further photoperiod extension in tomatoes. Our previous research indicated the response of cucumbers to long photoperiod of lighting varies with light spectrum. Therefore, we set out to examine greenhouse tomato production under supplemental CL using an alternating red (200 μmol m?2 s?1, 06:00–18:00) and blue (50 μmol m?2 s?1, 18:00–06:00) spectrum in comparison to a 12 h supplemental lighting treatment with a red/blue mixture (200 μmol m?2 s?1 red + 50 μmol m?2 s?1 blue, 06:00–18:00) at the same DLI. Our results indicate that tomato plants grown under supplemental CL using the red and blue alternating spectrum were injury-free. Furthermore, parameters related to photosynthetic performance (i.e., Pnmax, quantum yield, and Fv/Fm) were similar between CL and 12 h lighting treatments indicating no detrimental effect of growth under CL. Leaves under CL produced higher net carbon exchange rates (NCER) during the subjective night period (18:00–06:00) compared to plants grown under 12 h lighting. Notably, 53 days into the treatment, leaves grown under CL produced positive NCER values (photosynthesis) during the subjective night period, a period typically associated with respiration. At 53 days into the growth cycle, it is estimated that leaves under CL will accumulate approximately 800 mg C m?2 more than leaves under 12 h lighting over a 24 h period. Leaves grown under CL also displayed similar diurnal patterns in carbohydrates (glucose, fructose, sucrose, and starch) as leaves under 12 h lighting indicating no adverse effects on carbohydrate metabolism under CL. Taken together, this study provides evidence that red and blue spectral alternations during CL allow for injury-free tomato production. We suggest that an alternating spectrum during CL may alleviate the injury typically associated with CL production in tomato.
关键词： photoperiod,light-emitting diodes,continuous lighting,tomato,spectral quality,greenhouse,net carbon exchange rate,supplemental lighting
更新于2025-09-12 10:27:22
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Fundamentals and Applications of Red Light-Emitting Diodes (LEDs) <i>In Vitro</i> Plant Growth on Tomato <i>Lycopersicon esculentum Mill</i>
摘要： The aim of these studies was mainly to investigate the effects of monochromatic LEDs applied singly on the in vitro plant growth and morphogenesis. Various morphological and physiological parameters are considered that influence the growth and development of plants in vitro under red LED light as compared to those under normal light. Upon exposure to LED, in vitro-raised plants have shown significant improvements in growth and morphogenesis. In particular, red and blue lights, either alone or in combination, have a significant influence on plant growth. The present study gives an overview of the fundamentals of LEDs and describes their effects on in vitro plant growth and morphogenesis and their future potentials. The main objective of this study was to carry out line and combing ability of plant growth on tomato.
关键词： Solid-state lighting,Light-emitting diode,In vitro morphogenesis,Spectral quality
更新于2025-09-11 14:15:04
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Extended multiplicative signal correction for FTIR spectral quality test and pre‐processing of infrared imaging data
摘要： Spectral quality control is an important step in the analysis of infrared spectral data, however, often neglected in scientific literature. A frequently used quality test that was originally developed for infrared spectra of bacteria is provided by OPUS software from Bruker Optik GmbH. In this study the OPUS quality test is applied to a large number of spectra of bacteria, yeasts and moulds and hyperspectral images of microorganisms. It is shown that the use of strict thresholds for parameters of the OPUS quality test leads to discarding too many spectra. A strategy for optimizing parameters thresholds of the OPUS quality test is provided and a novel approach for spectral quality testing based on Extended Multiplicative Signal Correction (EMSC) is suggested. For all the data sets considered in our study, the EMSC quality test is shown to be the best among different alternatives of OPUS quality test provided.
关键词： Extended Multiplicative Signal Correction,infrared spectroscopy,spectral quality test
更新于2025-09-11 14:15:04