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- 2017
- photosynthesis
- dry matter
- gas exchange
- chlorophyll content
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- Agronomy
- University of Basilicata
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Comprehensive Remote Sensing || Solar Induced Chlorophyll Fluorescence: Origins, Relation to Photosynthesis and Retrieval
摘要： Photosynthesis has been key to Earth’s habitability, especially since the evolution of oxygenic photosynthesis with the accompanying rise in atmospheric O2 starting in the Proterozoic era, around 2.5 billion years ago. The conversion of light to chemical energy enables higher life forms and the presence of reduced carbon stocks and molecular O2 (accumulated products of photosynthesis) provided the fossil fuels for the initiation of our industrialized society. As a visible indicator of photosynthesis, fluorescence emanating from chlorophyll molecules attracted interest more than 100 years ago. In 1874, red fluorescence from a green living leaf was observed to be weaker than from a dilute chlorophyll solution (Müller, 1874), indicating an alternate fate for energy absorbed by chlorophyll in vivo. More quantitative studies of chlorophyll a fluorescence go back to observations by Hans Kautsky and A. Hirsch in 1931 at the Chemical Institute at the University of Heidelberg, Germany (Kautsky, 1931). They discovered the so-called Kautsky effect, a decrease in Chl fluorescence following illumination of dark-adapted leaves. Both studies already indicated an important aspect of chlorophyll fluorescence, namely, that its yield can vary. This effect is caused by variation in the balance of pathways that compete with fluorescence for quenching of the excited chlorophyll state. The porphyrin ring of the chlorophyll molecule is the center of light absorption and fluorescence. In a dilute chlorophyll solution, where fluorescence is the only route for de-excitation, the fluorescence lifetime (sF) is about 6 ns and the fluorescence yield (FF) approaches 1. In vivo, the excited chlorophyll state can be quenched by other processes, most notably photosynthesis itself but also quenching to heat; FF is lower (1%–5%) and the sF proportionally shorter. Fluorescence in itself is not a significant route for de-excitation of chlorophyll but changes in FF or sF can be used to study how absorbed energy is used. On the other hand, when FF is constant, fluorescence can provide information on the total amount of light absorbed, as the amount emitted will be proportional to the total amount of photosynthetically active radiation (PAR) that is absorbed by chlorophyll and associated pigments. Fig. 1 shows an example of a typical fluorescence spectrum as well as the absorbance spectrum by chlorophyll.
关键词： Fluorescence Yield,Solar Induced Chlorophyll Fluorescence,Chlorophyll,Photosynthesis,Remote Sensing
更新于2025-09-04 15:30:14
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Stability study of natural green dye based DSSC
摘要： Evolution of solar cell based on natural molecules flourished expeditiously, which is a good alternative for silicon-based solar cells or thin film technologies due to their low assembling cost, lightweight and flexibility. But natural dye-based dye-sensitized solar cell (DSSC) has low cell efficiency and stability, which limits the use of organic solar cells. In this research, natural green dye extracted from spinach (Spinacia oleracea) and used as a sensitizer source for natural dye-based DSSC. The measured cell efficiency of natural green dye-sensitized DSSC was 0.398%. Also, the cell stability test has been carried out by measuring the degradation rate (cell efficiency) by aging the dye molecule for DSSC has been conducted after 48, 96, 144 and 196 hours under 100mW/cm2 illumination (1.5 AM) at the ambient condition.
关键词： natural green dye,degradation,DSSC,chlorophyll,TiO2,stability
更新于2025-09-04 15:30:14
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Smart Plant Factory (The Next Generation Indoor Vertical Farms) || Detection and Utilization of Biological Rhythms in Plant Factories
摘要： Biological rhythms with a period of about 24 h, called “circadian rhythms,” are generated by the expressions of clock genes. In plants, circadian rhythms increase the growth rate through the daily coordination of photosynthesis and metabolism. Therefore, the detection and utilization of circadian rhythms is required to improve the plant production in plant factories. In this chapter, recently developed technologies based on circadian rhythms are described. Section 22.1 focuses on seedling diagnosis using the circadian rhythm of chlorophyll ?uorescence (CF). Section 22.2 describes high-throughput growth prediction systems based on the circadian rhythm of CF. Section 22.3 provides examples of global analysis of acquired gene expression as biological information and methods for analyzing internal time (i.e., the phases of circadian rhythms) using that data. We describe how circadian rhythms can be observed by comprehensive analyses and the methods used for such analyses. Finally, Sect. 22.4 describes a basic theory for controlling circadian rhythms by environmental stimuli. Methods that enable basic control of circadian rhythms are important, as they are applicable to a variety of research questions and industrial problems.
关键词： Molecular timetable method,Circadian rhythms,Phase response curves,Growth prediction,Chlorophyll ?uorescence,Transcriptome analysis
更新于2025-09-04 15:30:14
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Influence of Cosine Corrector and Uas Platform Dynamics on Airborne Spectral Irradiance Measurements
摘要： Measuring solar-induced chlorophyll fluorescence from small-sized Unmanned Aircraft Systems (UAS) can potentially fill the scaling gap between ground-based and airborne/space-borne observations. These measurements require well calibrated, high-spectral resolution spectroradiometers and precise measurements of vegetation radiance and incoming solar irradiance. Here we present a system equipped with a spectroradiometer with a split optical path that measures incoming irradiance through a cosine corrector/diffuser. The objectives of this study are to characterise cosine corrected solar irradiance measurements with regard to sensor homogeneity and possible offset from an ideal cosine response. We further suggest a methodology to calculate a corrected zenith angle that accounts for changing sensor orientation due to pitch, roll and heading of the UAS platform during flight. We found that the cosine corrector is sufficiently homogeneous, thus measurements are independent of UAS heading. The response follows the cosine law for zenith angles, however, the sensor significantly underestimated irradiance for zenith angles >10?, with overall cosine errors ranging from 0.991 to 1.229. Yet, typical in-flight platform pitch and roll angles produce a zenith angle offset of up to 6? in low wind conditions. Cosine sensor measurements corrected for the zenith angle offset and the cosine error resulted in a 1.7% change in irradiance.
关键词： irradiance cosine corrector,spectroradiometer,sun zenith angle,solar-induced chlorophyll fluorescence,unmanned aircraft system
更新于2025-09-04 15:30:14
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A Method to Reconstruct the Solar-Induced Canopy Fluorescence Spectrum from Hyperspectral Measurements
摘要： A method for canopy Fluorescence Spectrum Reconstruction (FSR) is proposed in this study, which can be used to retrieve the solar-induced canopy fluorescence spectrum over the whole chlorophyll fluorescence emission region from 640–850 nm. Firstly, the radiance of the solar-induced chlorophyll fluorescence (Fs) at five absorption lines of the solar spectrum was retrieved by a Spectral Fitting Method (SFM). The Singular Vector Decomposition (SVD) technique was then used to extract three basis spectra from a training dataset simulated by the model SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes). Finally, these basis spectra were linearly combined to reconstruct the Fs spectrum, and the coefficients of them were determined by Weighted Linear Least Squares (WLLS) fitting with the five retrieved Fs values. Results for simulated datasets indicate that the FSR method could accurately reconstruct the Fs spectra from hyperspectral measurements acquired by instruments of high Spectral Resolution (SR) and Signal to Noise Ratio (SNR). The FSR method was also applied to an experimental dataset acquired in a diurnal experiment. The diurnal change of the reconstructed Fs spectra shows that the Fs radiance around noon was higher than that in the morning and afternoon, which is consistent with former studies. Finally, the potential and limitations of this method are discussed.
关键词： Fluorescence Spectrum Reconstruction (FSR),solar-induced chlorophyll fluorescence (Fs),Spectral Fitting Method (SFM),Fraunhofer Line Discriminator (FLD),hyperspectral remote sensing,Singular Vector Decomposition (SVD)
更新于2025-09-04 15:30:14
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Long-Term Preservation of Microalgal Cells and their Optical Properties
摘要： A unique protocol using a gelatin-based embedding technique allows long-term preservation of sea ice microalgae and phytoplankton cells. The high quality preservation of the cells and their optical properties for over two decades was confirmed after a re-examination of samples collected and prepared during 1987 at McMurdo Station, Antarctica and during 1990 at the California Bight near Los Angeles. Samples stored frozen until 2011 demonstrated the long-term preservation of the cellular structure, as well as their spectral absorption and fluorescence properties. This protocol makes it possible to assemble archives of sea ice microalgae and phytoplankton cells for environmental studies.
关键词： Absorption,Chlorophyll,Microalgae,Fluorescence
更新于2025-09-04 15:30:14
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SENSITIVITY TO ENVIRONMENTAL STRESS OF PRATA,JAPIRA AND VITóRIA BANANA CULTIVARS PROVEN BY CHLOROPHYLL a FLUORESCENCE
摘要： This study aimed to evaluate the physiological responses to environmental stress during pre- and post-harvest of the following banana cultivars: Prata (AAB), Japira (AAAB) and Vitoria (AAAB). Analyses were carried out on young plants at vegetative stage (daughter-plant) and adult plants at reproductive stage (mother-plant). The experimental design was completely randomized. In the in vivo pre-harvest analysis were used seven replications, in a factorial scheme (3x2x2), three cultivars and two stages (vegetative and reproductive) and two collection periods (March and June). For the analysis of post-harvest quality were used five replications in a factorial design (3x2x5), corresponding to three cultivars, two development stages and five periods of post-harvest analysis, carried out every two days from stage 4 of fruit ripening. The chlorophyll a fluorescence emission kinetics showed low photochemical performance of the three cultivars in June, a period characterized by lower temperatures and water deficit. Prata was the cultivar with the lowest tolerance to abiotic physiological behavior changes, which also reflected in fruit quality, because there was a change in physical and physicochemical parameters. Japira and Vitoria cultivars showed similar physiological responses in the pre- and post-harvest periods, according to their phylogenetic proximity. The total performance index, i.e., the conservation of energy absorbed by PSII up to the reduction of the final PSI acceptors (PItotal) and the di-malonic aldehyde (MDA) content were significantly higher in Japira and Vitoria cultivars compared to Prata cultivar in the reproductive phase. There was no significant change in the potential quantum efficiency of PSII (FV / FM = jP0) among the three cultivars. It was concluded that Japira and Vitoria cultivars showed greater plasticity to tolerate or even adapt to abiotic variations keeping higher fruit yield. PItotal is the most sensitive parameter during the banana life cycle and important tool for distinguishing different cultivars yields.
关键词： Chlorophyll fluorescence,Musa spp.,post-harvest quality,lipid peroxidation,pigments
更新于2025-09-04 15:30:14
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Remote Estimation of Chlorophyll-a in Inland Waters by a NIR-Red-Based Algorithm: Validation in Asian Lakes
摘要： Satellite remote sensing is a highly useful tool for monitoring chlorophyll-a concentration (Chl-a) in water bodies. Remote sensing algorithms based on near-infrared-red (NIR-red) wavelengths have demonstrated great potential for retrieving Chl-a in inland waters. This study tested the performance of a recently developed NIR-red based algorithm, SAMO-LUT (Semi-Analytical Model Optimizing and Look-Up Tables), using an extensive dataset collected from five Asian lakes. Results demonstrated that Chl-a retrieved by the SAMO-LUT algorithm was strongly correlated with measured Chl-a (R2 = 0.94), and the root-mean-square error (RMSE) and normalized root-mean-square error (NRMS) were 8.9 mg?m?3 and 72.6%, respectively. However, the SAMO-LUT algorithm yielded large errors for sites where Chl-a was less than 10 mg?m?3 (RMSE = 1.8 mg?m?3 and NRMS = 217.9%). This was because differences in water-leaving radiances at the NIR-red wavelengths (i.e., 665 nm, 705 nm and 754 nm) used in the SAMO-LUT were too small due to low concentrations of water constituents. Using a blue-green algorithm (OC4E) instead of the SAMO-LUT for the waters with low constituent concentrations would have reduced the RMSE and NRMS to 1.0 mg?m?3 and 16.0%, respectively. This indicates (1) the NIR-red algorithm does not work well when water constituent concentrations are relatively low; (2) different algorithms should be used in light of water constituent concentration; and thus (3) it is necessary to develop a classification method for selecting the appropriate algorithm.
关键词： Asian lakes,blue-green algorithms,chlorophyll-a concentration,accuracy assessment,NIR-red algorithms
更新于2025-09-04 15:30:14
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Wavelength selection of the multispectral lidar system for estimating leaf chlorophyll and water contents through the PROSPECT model
摘要： The estimation of leaf biochemical constituents is of high interest for the physiological and ecological applications of remote sensing. The multispectral lidar (MSL) system emerges as a promising active remote sensing technology with the ability to acquire both three-dimensional and spectral characteristics of targets. The detection wavelengths of the MSL system can be geared toward the specific application purposes. Therefore, it’s important to conduct the wavelength selection work to maximize the potential of the MSL system in vegetation monitoring. Traditional strategies of wavelength selection attempt to establish an empirical relationship between large quantities of observed reflectance and foliar biochemical constituents. By contrast, this study proposed to select wavelengths through the radiative transfer model PROSPECT. A five-wavelength combination was established to estimate leaf chlorophyll and water contents: 680, 716, 1104, 1882 and 1920 nm. The consistency of the wavelengths selected were tested by running different versions of PROSPECT model. Model inversion using simulated and experimental datasets showed that the selected wavelengths have the ability to retrieve leaf chlorophyll and water contents accurately. Overall, this study demonstrated the potential of the MSL system in vegetation monitoring and can serve as a guide in the design of new MSL systems for the application community.
关键词： Multispectral lidar,Wavelength selection,Leaf water content,Leaf chlorophyll content,PROSPECT model
更新于2025-09-04 15:30:14
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Effects of UV-C radiation on common dandelion and purple coneflower: First results
摘要： Ultraviolet-C (UV-C) light (100 ≤ λ ≤ 280 nm) is a ionizing radiation that can damage living organisms. An experiment was conducted on plants of common dandelion (Taraxacum officinale Weber, T. Densleonis Desf.) and purple coneflower [Echinacea purpurea, (L.) Moench] irradiated with UV-C at different exposition times, under controlled conditions and grown in self-produced characterized compost, to assess the effect of different doses UV-C radiation on some physiological parameters. Trials have been carried out using a black chamber equipped with an UV-C lamp in which plants were divided in four groups on the basis of UV-C irradiation period (10, 30, 60, and 120 min). Non-irradiated plants were kept as controls. Plant photosynthetic performance, chlorophyll content (SPAD) and some morphologic traits were recorded before, immediately after irradiations and 20 days weeks later. The effects on photosynthetic performances and chlorophyll contents (SPAD) were evaluated and compared with data obtained in similar experiments where tomato plants were irradiated at different times with UV-C light. In both species, SPAD values decreased as the irradiation period became longer. The two species showed different gas exchange dynamics, depending on the UV-C exposure time. Two months after the UV-C irradiation, plant dry weight measured at 120-min UV-C exposure was significantly lower than the control.
关键词： photosynthesis,dry matter,gas exchange,chlorophyll content,ozone layer.
更新于2025-09-04 15:30:14