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Photosynthetically Active Radiation: Measurement and Modeling. Figure 4 Decomposing the absorption spectrum of a water sample. Spectra of the absorption coefficients corresponding to pure fresh water [59]; 1.0 Â 10 À3 mg m À3 yellow substance (specific absorption coefficient at 380 nm 0.565 L mg À1 nm À1 ); 1.0 mg m À3 chlorophyll-a (phytoplankton, [60]); and detritus (from the measured data of [61]). The total absorption of the water sample is plotted with a bold line

Photosynthetically Active Radiation: Measurement and Modeling. Figure 4 Decomposing the absorption spectrum of a water sample. Spectra of the absorption coefficients corresponding to pure fresh water [59]; 1.0 Â 10 À3 mg m À3 yellow substance (specific absorption coefficient at 380 nm 0.565 L mg À1 nm À1 ); 1.0 mg m À3 chlorophyll-a (phytoplankton, [60]); and detritus (from the measured data of [61]). The total absorption of the water sample is plotted with a bold line

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... Over the IMAGINES sites, only part of the sites' FAPAR corresponded to the instantaneous black-sky values at 10:00 AM, whereas the FAPAR values over other sites corresponded to the daily integrated black-sky FAPAR. Considering that instantaneous FAPAR at the time of the satellite overpass (around 10:00 AM) is a good approximation of daily integrated black-sky FAPAR [21,36], the instantaneous and daily integrated black-sky FAPAR values of high-resolution reference maps at the VALERI and IMAGINES sites were chosen to evaluate the MODIS, MUSES and EBR black-sky FAPAR products. Consequently, 58 high-resolution FAPAR reference maps over 36 VALERI and IMAGINES sites were used in this study. ...
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The fraction of absorbed photosynthetically active radiation (FAPAR) is a key biophysical variable directly associated with the photosynthetic activity of plants. Several global FAPAR products with different spatial resolutions have been generated from remote sensing data, and much work has focused on validating them. However, those studies have primarily evaluated global FAPAR products at a spatial resolution of 1 km or more, whereas few studies have evaluated the global 500 m resolution FAPAR product distributed in recent years. Furthermore, there are a few FAPAR products, including black-sky, white-sky and blue-sky FAPAR datasets, and almost no studies have evaluated these products. In this article, three global FAPAR products at 500 m resolution, namely MODIS (only black-sky FAPAR), MUSES and EBR (black-sky, white-sky and blue-sky FAPAR) were compared to evaluate their temporal and spatial discrepancies and direct validation was conducted to compare these FAPAR products with the FAPAR values derived from the high-resolution reference maps from the Validation of Land European Remote Sensing Instrument (VALERI) and Implementing Multi-Scale Agricultural Indicators Exploiting Sentinels (IMAGINES) projects. The results showed that the MUSES FAPAR product exhibited the best spatial integrity, whereas the MODIS and EBR FAPAR products had many missing pixels in the equatorial rainforest regions and at high latitudes in the Northern Hemisphere. The MODIS, MUSES and EBR FAPAR products were generally consistent in their spatial patterns. However, a relatively large discrepancy among these FAPAR products was present in the equatorial rainforest regions and the middle and high latitude regions where the main vegetation type was forest. The differences between the black-sky and white-sky FAPAR datasets at the global scale were significant. In January, the MUSES and EBR black-sky FAPAR values were larger than their white-sky FAPAR values in the region north of 30° north latitude but they were smaller than their white-sky FAPAR values in the region south of 30° north latitude. In July, the MUSES and EBR black-sky FAPAR values were lower than their white-sky FAPAR values in the region north of 30° south latitude and they were larger than their white-sky FAPAR values in the region south of 30° south latitude. The temporal profiles of the MUSES FAPAR product were continuous and smooth, whereas those of the MODIS and EBR FAPAR products showed many fluctuations, particularly during the growing seasons. Direct validation indicated that the MUSES FAPAR product had the best accuracy (R2 = 0.6932, RMSE = 0.1495) compared to the MODIS FAPAR product (R2 = 0.6202, RMSE = 0.1710) and the EBR FAPAR product (R2 = 0.5746, RMSE = 0.1912).
... PAR measurement is important in agriculture in order to evaluate the growth of the plant and it is recorded in the field using a light quantum sensor (Rosati and Dejong, 2003). The PAR measured inside the nets includes the PAR that passed directly via the pores of the nets and the diffused PAR (Al-Helal et al., 2010;Mõttus, et al., 2012). The PAR under the photo-selective nets differs according to the shading intensity. ...
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Photo selective shade net is a product made of plastic fibers connected together with each other, forming a regular porous structure and allowing gases, liquid and light to pass through. It has a capacity to selectively filter the intercepted solar radiation, in addition to their protective function. Vegetables are considered as protective food which are highly perishable in nature. High temperature due to global warming, climate change and excessive use of chemicals are some of the burning issues of vegetable production. Photo selective shade net can be a partial solution for these problems. Vegetable crops grown under different photo selective shade net shows productive responses thus by application of various Photo selective shade nets we can improve the quality as well as production of vegetable crops.
... The part of electromagnetic radiation that can be used as the source of energy for photosynthesis by green plants is the photosynthetically active radiation (PAR). It is expressed either in terms of the photosynthetic photon flux density (PPFD) (mmol photons, m −2 s −1 ), or in photosynthetically active radiation (PAR) (mmol m −2 s −1 or W/m 2 ) [46]. PAR irradiance depends upon several factors, such as the meteorological seasonal conditions, the geographical conditions, and the conceptual greenhouse characteristics. ...
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This work is motivated by the difficulty of cultivating crops in horticulture greenhouses under hot and arid climate conditions. The main challenge is to provide a suitable greenhouse indoor environment, with sufficiently low costs and low environmental impacts. The climate control inside the greenhouse constitutes an efficient methodology for maintaining a satisfactory environment that fulfills the requirements of high-yield crops and reduced energy and water resource consumption. In hot climates, the cooling systems, which are assisted by an effective control technique, constitute a suitable path for maintaining an appropriate climate inside the greenhouse, where the required temperature and humidity distribution is maintained. Nevertheless, most of the commonly used systems are either highly energy or water consuming. Hence, the main objective of this work is to provide a detailed review of the research studies that have been carried out during the last few years, with a specific focus on the technologies that allow for the enhancement of the system effectiveness under hot and arid conditions, and that decrease the energy and water consumption. Climate control processes in the greenhouse by means of manual and smart control systems are investigated first. Subsequently, the different cooling technologies that provide the required ranges of temperature and humidity inside the greenhouse are detailed, namely, the systems using heat exchangers, ventilation, evaporation, and desiccants. Finally, the recommended energy-efficient approaches of the desiccant dehumidification systems for greenhouse farming are pointed out, and the future trends in cooling systems, which include water recovery using the method of combined evaporation–condensation, as well as the opportunities for further research and development, are identified as a contribution to future research work.
... Considering the above, the most appropriate measurement variable, when working with plants, is the Photosynthetic Photon Flux Density (PPFD), with µmol m −2 s −1 as its unit. This is the amount of power of the electromagnetic radiation received on a surface measured as the number of photons in the PAR region of the spectrum received in a square meter per second [118]. This variable can be measured with affordable PAR sensors which are manufactured to offer a response in which each photon is equally absorbed considering that photons of shorter wavelength (higher frequency) have more energy than photons of longer wavelength. ...
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In the last decades, lighting installations in plant tissue culture have generally been renewed or designed based on LED technology. Thanks to this, many different light quality advances are available but, with their massive implementation, the same issue is occurring as in the 1960s with the appearance of the Grolux (Sylvania) fluorescent tubes: there is a lack of a methodological standardization of lighting. This review analyzes the main parameters and variables that must be taken into account in the design of LED-based systems, and how these need to be described and quantified in order to homogenize and standardize the experimental conditions to obtain reproducible and comparable results and conclusions. We have designed an experimental system in which the values of the physical environment and microenvironment conditions and the behavior of plant tissue cultures maintained in cabins illuminated with two lighting designs can be compared. Grolux tubes are compared with a combination of monochromatic LED lamps calibrated to provide a spectral emission, and light irradiance values similar to those generated by the previous discharge lamps, achieving in both cases wide uniformity of radiation conditions on the shelves of the culture cabins. This study can help to understand whether it is possible to use LEDs as one standard lighting source in plant tissue culture without affecting the development of the cultures maintained with the previously regulated protocols in the different laboratories. Finally, the results presented from this caparison indicate how temperature is one of the main factors that is affected by the chosen light source.
... The resulting NEI E d for PAR is equal to 0.03 µmol photons m −2 s −1 . ER is 5% for PAR [40] and 2% for E d (λ) following previous calibration error estimations [41,42]. ...
... The resulting for PAR is equa 0.03 µ mol photons m −2 s −1 . ER is 5% for PAR [40] and 2% for Ed(λ) following previo calibration error estimations [41,42]. ...
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Measuring the underwater light field is a key mission of the international Biogeochemical-Argo program. Since 2012, 0-250 dbar profiles of downwelling irradiance at 380, 412 and 490 nm besides photosynthetically available radiation (PAR) have been acquired across the globe every 1 to 10 days. The resulting unprecedented amount of radiometric data has been previously quality-controlled for real-time distribution and ocean optics applications, yet some issues affecting the accuracy of measurements at depth have been identified such as changes in sensor dark responsiveness to ambient temperature, with time and according to the material used to build the instrument components. Here, we propose a quality-control procedure to solve these sensor issues to make Argo radiometry data available for delayed-mode distribution, with associated error estimation. The presented protocol requires the acquisition of ancillary radiometric measurements at the 1000 dbar parking depth and night-time profiles. A test on >10000 profiles from across the world revealed a quality-control success rate >90% for each band. The procedure shows similar performance in re-qualifying low radiometry values across diverse oceanic regions. We finally recommend, for future deployments, acquiring daily 1000 dbar measurements and one night profile per year, preferably during moonless nights and when the temperature range between the surface and 1000 dbar is the largest.
... Otra restricción importante para el cultivo del arroz en el mundo es la radiación solar. En general, las plantas tienen la capacidad de utilizar sólo parte del total del espectro electromagnético que entrega el sol, la que corresponde a la radiación fotosintéticamente activa (Mottus et al., 2013). Esta radiación (400 y 700 nm) contribuye al crecimiento y desarrollo adecuado de las plantas y es absorbida por la clorofila a, b y carotenoides presentes en la planta (McCree, 1972a;1972b). ...
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La distribución de los organismos vivos, como plantas y animales, es influenciada fuertemente por las condiciones climáticas (Aguirre-Gutiérrez et al., 2015). En el caso específico del arroz (Oryza sativa L.), éste ha logrado adaptarse a una gran cantidad de ambientes, con diferentes condiciones climáticas. Las principales restricciones climáticas asociadas a la productividad del cultivo del arroz en el mundo son la temperatura y la radiación solar (Fahad et al., 2019). El arroz es un cultivo de origen tropical y, por ello, normalmente requiere de temperaturas que varíen entre 20 y 35 °C durante gran parte de su desarrollo (Cuadro 1) (Yoshida, 1981). Sin embargo, existen excepciones en donde la planta de arroz ha logrado adaptarse a condiciones de bajas temperaturas en diversas regiones del planeta. De las dos principales subespecies de arroz existentes, la subespe-cie japonica logra desarrollarse exitosamente en climas templados como el norte de China, Japón, Corea y Chile, permitiendo que el cultivo se desarrolle fuera de zonas tropicales o subtropicales, donde se desarrolla comúnmente el arroz de la subespecie indica (Takahashi, 1984). Temperaturas inferiores a 15 °C tienen efectos negativos para el cultivo del arroz. El nivel de daño causado por este estrés depende del tiempo de exposición, intensidad del estrés y de la etapa del desarrollo en que se encuentre el arroz (Howarth y Ougham, 1993; Fujino et al.
... This formulation considers water depth in the reactor, biomass density and light extinction coefficients of both water and biomass. In both equations, we multiplied I 0 by a 0.43 PAR constant, representing the ratio of the sunlight which is suitable for photosynthesis 61 . ...
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Multi-scale macroalgae growth models are required for the efficient design of sustainable, economically viable, and environmentally safe farms. Here, we develop a multi-scale model for Ulva sp. macroalgae growth and nitrogen sequestration in an intensive cultivation farm, regulated by temperature, light, and nutrients. The model incorporates a range of scales by incorporating spatial effects in two steps: light extinction at the reactor scale (1 m) and nutrient absorption at the farm scale (1 km). The model was validated on real data from an experimental reactor installed in the sea. Biomass production rates, chemical compositions, and nitrogen removal were simulated under different seasons, levels of dilution in the environment and water-exchange rate in the reactor. This multi-scale model provides an important tool for environmental authorities and seaweed farmers who desire to upscale to large bioremediation and/or macroalgae biomass production farms, thus promoting the marine sustainable development and the macroalgae-based bioeconomy.
... APAR is a product of incoming total Photosynthetic Active Radiation (PAR) and a fraction of PAR absorbed (i.e. fAPAR) by photosynthetic molecules (Mõttus et al., 2012). fAPAR is an uncertain quantity as it includes the diffuse radiation and excludes the PAR reflected by vegetation, which is difficult to compute (Zhao et al., 2016). ...
Article
Eddy covariance Fluorescence quantum yield Light use efficiency SCOPE PAM Fluorometer Radiative Transfer Model A B S T R A C T Reliable estimation of forest carbon fluxes in space and time is a major challenge. Sun-Induced Chlorophyll Fluorescence (SIF) has been found closely linked to vegetation photosynthetic activity. But the application of SIF for direct estimation of Gross Primary Productivity (GPP) is not well investigated. In this study, we demonstrate the estimation of GPP for tropical deciduous forests located in North Western Himalayan Foothills in India using simulated SIF and fluorescence quantum yield (ФF) through a modified Light Use Efficiency (LUEf) model. SIF simulated using Soil Canopy Observation, Photochemistry, and Energy fluxes (SCOPE) model provided the estimate of Photosynthetically Active Radiation (PAR) intercepted by the canopy foliage and ФF. ФF, measured through the Pulse-Amplitude Modulated (PAM) fluorometer quantifies the emission rate of SIF per unit of the absorbed photon. The integration of these factors into the proposed LUEf model offered real-time photosynthetic efficiency and improved the estimate of GPP of the deciduous forest. The results show that GPP estimated from SIF (SIF TOC) was closely related to GPP Eddy with R 2 = 0.91 (p<0.05) with RMSE= 29.24 gC m − 2 month − 1 than GPP estimated from LUE model (R 2 =0. 79, p<0.05) and RMSE = 96.25 gC m − 2 month − 1). GPP MODIS underestimated the GPP with a non-significant correlation to GPP Eddy for all the months with R 2 =0. 36 (p<0.05) and RMSE = 188.96 gC m − 2 month − 1. The results obtained are promising and the proposed model can be used for estimating carbon fluxes of forests over a larger spatial scale using satellite-derived SIF.
... There is no official SI unit for photon flux density measurement PPFD. Thus, in Equation (1), a mole of photons is used to designate Avogadro's number (N A = 6.022 141 · 10 23 mol −1 ) of photons for stoichiometry [32,33]. The unit µmol · m −2 · s −1 is most suitable for PPF, since it accounts for the number of photons in the PAR spectral range [34,35]. ...
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We report a methodological approach for simulating luminary output radiation, which is achieved by mixing light-emitting diodes (LEDs) in order to match any plant absorption spectrum. Various recorded narrow-band LED spectra of different colors were first characterized and then fitted with a multi-Gaussian model. An optimizing procedure computed the optimal weighting of the relevant parameters so as to minimize the discrepancy between the combined spectrum and the reference target curve. The particle swarm optimization (PSO) method was applied because it is the most suitable technique for mono-objective situations. Within the useful spectral interval, the worst relative standard deviation between the optimized curve and recorded LED spectral power distribution (SPD) was 3.4%. When combining different LED types, the simulated light output showed that we could limit ourselves to selecting only five colored sources. This work will help us to design an optimized 200W laboratory luminaire with a pulse-width switched-mode power supply.
... Because of the strong absorption of PAR radiation by the photosynthetic pigments, multiple scattering contributes only marginally to the radiative transfer, and FAPAR can be closely approximated by the fraction of PAR intercepted by the photosynthetically active radiation (FIPAR) elements of canopies. This approximation is well verified for wheat that does not present glossy or hairy leaves (Andrieu and Baret, 1993;Mõttus et al., 2013). ...
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Canopy light interception determines the amount of energy captured by a crop, and is thus critical to modelling crop growth and yield, and may substantially contribute to the prediction uncertainty of crop growth models (CGMs). We thus analyzed the canopy light interception models of the 26 wheat (Triticum aestivum) CGMs used by the Agricultural Model Intercomparison and Improvement project (AgMIP). Twenty-one CGMs assume that the light extinction coefficient (K) is constant, varying from 0.37 to 0.80 depending on the model. The other models take into account the illumination conditions and assume either that all green surfaces in the canopy have the same inclination angle (θ) or that θ distribution follows a spherical distribution. These assumptions have not yet been evaluated due to a lack of experimental data. Therefore, we conducted a field experiment with five cultivars with contrasting leaf stature sown at normal and double row spacing, and analyzed θ distribution in the canopies from 3-dimensional canopy reconstructions. In all the canopies, θ distribution was well represented by an ellipsoidal distribution. We thus carried out an intercomparison between the light interception models of the AgMIP-Wheat CGMs ensemble and a physically based K model with ellipsoidal leaf angle distribution and canopy clumping (KCell). Results showed that the (KCell) model outperformed current approaches under most illumination conditions and that the uncertainty in simulated wheat growth and final grain yield due to light models could be as high as 45%. Therefore, our results call for an overhaul of light interception models in CGMs.