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- 2017
- photosynthesis
- dry matter
- gas exchange
- chlorophyll content
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- Agronomy
- University of Basilicata
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Excitation energy transfer in the far-red absorbing violaxanthin/vaucheriaxanthin chlorophyll a complex from the eustigmatophyte alga FP5
摘要： This work highlights spectroscopic investigations on a new representative of photosynthetic antenna complexes in the LHC family, a putative violaxanthin/vaucheriaxanthin chlorophyll a (VCP) antenna complex from a freshwater Eustigmatophyte alga FP5. A representative VCP-like complex, named as VCP-B3 was studied with both static and time-resolved spectroscopies with the aim of obtaining a deeper understanding of excitation energy migration within the pigment array of the complex. Compared to other VCP representatives, the absorption spectrum of the VCP-B3 is strongly altered in the range of the chlorophyll a Qy band, and is substantially red-shifted with the longest wavelength absorption band at 707 nm at 77 K. VCP-B3 shows a moderate xanthophyll-to-chlorophyll a efficiency of excitation energy transfer in the 50–60% range, 20–30% lower from comparable VCP complexes from other organisms. Transient absorption studies accompanied by detailed data fitting and simulations support the idea that the xanthophylls that occupy the central part of the complex, complementary to luteins in the LHCII, are violaxanthins. Target analysis suggests that the primary route of xanthophyll-to-chlorophyll a energy transfer occurs via the xanthophyll S1 state.
关键词： Chlorophyll a,Light-harvesting complex,Transient absorption,Violaxanthin,Photosynthesis,Vaucheriaxanthin
更新于2025-11-19 16:46:39
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Imaging Spectrometry and Fluorometry in Support of Flex: What Can We Learn from Multi-Scale Experiments?
摘要： In advance of the FLEX mission, experimental studies are needed to better understand the factors driving Solar-Induced Fluorescence (SIF) emission from vegetation across different temporal and spatial scales. Here, we present findings from boreal (evergreen and deciduous) forest trees and Midwestern (annual) crops, illustrating effects of seasonal downregulation and drought on the fluorescence signals. Further work is needed to develop defensible, quantitative fluorescence measurements, and to partition the drivers of the fluorescence signals into effects of structure and physiology.
关键词： chlorophyll fluorescence (SIF, Fs),stress,photosynthesis,drought,temperature,chlorophyll/carotenoid pigments
更新于2025-09-23 15:23:52
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Electronic Structure of Chlorophyll a Solution Investigated by Photoelectron Yield Spectroscopy
摘要： Various bio-related processes are driven by electron transfer reactions. Therefore the electronic structures of bio-molecules in their living environment are keys of their functionalities. One significant example photosynthesis which has attracted much attention due to urgent necessity of clean energy source. In this study, we carried out photoelectron yield spectroscopy (PYS) measurements to demonstrate the electronic structures of oligomerizedChl-a molecules, which is known as an essential reaction center of the photosystem in general green plants, under the atmospheric environment. The ionization energies of the Chl-a aggregates are successfully derived.
关键词： Photoelectron Yield Spectroscopy,Polarization energy,Light harvesting antenna,Photosynthesis,Photosystem,Electronic structure,Ionization energy,Reaction center,Chlorophyll a
更新于2025-09-23 15:23:52
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Practical Performance and Prospect of Underwater Optical Wireless Communication
摘要： Underwater optical wireless communication has been merely a theory for a long time because light sources are too weak to use them as emitters for communications. In the past decade, however, underwater optical wireless communications have used laser diodes or light emitting diodes as emitters with visible light in high brightness with low power consumption. Recently, they have become practical. As described in this paper, recent trends of underwater optical wireless communication study, practical modems and prospective uses of underwater optical wireless communication are presented first. Next, optical characteristics of the seawater in various conditions are explained based on the experimental data measured using the profiler for underwater optics produced especially for this study. Then the prototype underwater optical wireless communication modem developed by our team is introduced. It was tested in several sea areas, which confirmed bi-directional communication in the 120 m range at 20 Mbps and a remote desktop connection between under water vehicles at 100 m range. In addition, one modem was set in air; other was set in water. The modems mutually communicated directly through the sea surface.
关键词： UOWC,turbidity,chlorophyll,LD,VLC
更新于2025-09-23 15:23:52
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Imaging analysis of chlorophyll fluorescence induction for monitoring plant water and nitrogen treatments
摘要： The objective of this study was to check whether different water and nitrogen treatments and, even the water-nitrogen coupling effect of plants could be correctly differentiated via chlorophyll a fluorescence image. We developed a classification method using the imaging analysis of chlorophyll a fluorescence induction based on Artificial Neural Network. The measurements were carried out on scheffera octophylla (Lour.) Harms, and the images were recorded at 690 nm with a high-resolution imaging device consisting of LEDs for an excitation at 460 nm and an Electron-Multiplying CCD camera. The effect of three different water and three different nitrogen treatments on the fluorescence parameters were obtained by hundreds of time-resolved fluorescence images. We used a Radial Basis Function neural network to model and test the sample data. The results showed that the different water and nitrogen statuses of plants were identified by the chlorophyll a fluorescence images and showed a high recognition accuracy. Compared with nitrogen, water had more of an influence on chlorophyll a fluorescence and was easier to identify. However, because the water and nitrogen restrict and promote each other, studying the coupling effect of water and nitrogen is necessary. Nine levels of water-nitrogen coupling plants were tested and classified. We discovered that a significant decrease on the classified accuracy was observed for the high nitrogen and low nitrogen treatments, while under a medium N-supply, the recognition rate was high. The method in this paper allowed plants to be classified under different water and nitrogen treatments, and has the potential to monitor the water and nitrogen coupling effect of plants in situ.
关键词： Artificial Neural Network,Classification,Recognition,Chlorophyll a Fluorescence
更新于2025-09-23 15:23:52
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Structural and Functional Consequences of the Weak Binding of Chlorin e6 to Bovine Rhodopsin
摘要： The chlorophyll-derivative chlorin e6 (Ce6) identified in the retinas of deep-sea ocean fish is proposed to play a functional role in red bioluminescence detection. Fluorescence and 1H NMR spectroscopy studies with the bovine dim-light photoreceptor, rhodopsin, indicate that Ce6 weakly binds to it with μM affinity. Absorbance spectra prove that red light sensitivity enhancement is not brought about by a shift in the absorbance maximum of rhodopsin. 19F NMR experiments with samples where 19F labels are either placed at the cytoplasmic binding site or incorporated as fluorinated retinal, indicate that the cytoplasmic domain is highly perturbed by binding, while little to no changes are detected near the retinal. Binding of Ce6 also inhibits G protein activation. Chemical shift changes in 1H,15N NMR spectroscopy of 15N-Trp labeled bovine rhodopsin reveal that Ce6 binding perturbs the entire structure. These results provide experimental evidence that Ce6 is an allosteric modulator of rhodopsin.
关键词： G protein coupled receptor,chlorophyll-derivative,porphyrin,night vision,light activation,photosensitization,bovine rhodopsin,Allosteric modulator
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Novel Effective Chlorophyll Indicator for Forest Monitoring Using Worldview-3 Multispectral Reflectance
摘要： This paper explores the feasibility of deriving multispectral-based effective chlorophyll indicators (MECIs) for foliage chlorophyll concentration (CHLS) estimation. An average fusion method was applied to simulate the multispectral reflectance of the WorldView-3 sensor using hyperspectral data. With the experimental data of CHLS and predictors derived from multispectral reflectance, a series of linear regression analyses were carried out to derive appropriate models for CHLS estimation. Accuracy measures of RMSE and PRMSE were used to evaluate the model performance. Results showed that the coastal-band based MECI (MECIc) and the blue-band based MECI (MECIb) were able to achieve an RMSE of 0.5657 mg/g and 0.5943 mg/g as well as a PRMSE of 36% and 38% respectively. Using the Red edge and Yellow reflectance based NDVI (NDVIREY) as a predictor, the model can reduce uncertainty and achieve an estimation of 0.4089 mg/g and 26% for RMSE and PRMSE respectively. The prediction error made by the CHLS-NDVIREY model and the CHLS-MECI model were 11% and 60% larger than 0.38 mg/g the RMSE of hyperspectral-based CHLS-ECI model. In summary, NDVIREY was able to achieve a better prediction at around a level of 75% accuracy (1-PRMSE) and therefore is able to be an effective indicator of CHLS for forest monitoring.
关键词： climate change,hyperspectral remote sensing,Chlorophyll indicator,multispectral remote sensing,forest health
更新于2025-09-23 15:22:29
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Seasonal variation in chlorophyll <i>a</i> fluorescence of <i>Butea monosperma</i>
摘要： This study was conducted to observe the seasonal variation trend in leaf chlorophyll a fluorescence of Butea monosperma tree belonging to Fabaceae family. Chlorophyll fluorescence parameters taken for the present study were NPQ = (FM/FM ?1) (non-photochemical quenching of chlorophyll fluorescence), Fv/Fm = Fm–Fo/Fm (maximum photochemical quantum yield of photosystem II) and qL = qp.F0?/F’ (coefficient of photochemical fluorescence quenching). Chlorophyll a fluorescence of Butea monosperma was measured with the help of JUNIOR-PAM, Chlorophyll Fluorometer, Heinz Walz GmbH, Germany in December (winter), May (summer) and August (rainy) seasons and also on day 1, day 10 and day 20 of December, May and August. The measurement revealed that the above three fluorescence parameters showed a seasonal variation trend, wherein NPQ and qL followed a similar variation trend while Fv/Fm showed a different trend. NPQ and qL values were maximum in the summer season followed by winter and rainy seasons, while Fv/Fm value was maximum in the rainy season followed by winter and summer seasons. The variations in chlorophyll a fluorescence in different seasons are due to different environmental conditions causing a different degree of stress to Butea monosperma plant in different seasons.
关键词： Fv/Fm,chlorophyll fluorescence,seasonal variation,qL,Butea monosperma,NPQ
更新于2025-09-23 15:22:29
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Retrieval of Chlorophyll a from Sentinel-2 MSI Data for the European Union Water Framework Directive Reporting Purposes
摘要： The European Parliament and The Council of the European Union have established the Water Framework Directive (2000/60/EC) for all European Union member states to achieve, at least, 'good' ecological status of all water bodies larger than 50 hectares in Europe. The MultiSpectral Instrument onboard European Space Agency satellite Sentinel-2 has suitable 10, 20, 60 m spatial resolution to monitor most of the Estonian lakes as required by the Water Framework Directive. The study aims to analyze the suitability of Sentinel-2 MultiSpectral Instrument data to monitor water quality in inland waters. This consists of testing various atmospheric correction processors to remove the influence of atmosphere and comparing and developing chlorophyll a algorithms to estimate the ecological status of water in Estonian lakes. This study shows that the Sentinel-2 MultiSpectral Instrument is suitable for estimating chlorophyll a in water bodies and tracking the spatial and temporal dynamics in the lakes. However, atmospheric corrections are sensitive to surrounding land and often fail in narrow and small lakes. Due to that, deriving satellite-based chlorophyll a is not possible in every case, but initial results show the Sentinel-2 MultiSpectral Instrument could still provide complementary information to in situ data to support Water Framework Directive monitoring requirements.
关键词： atmospheric correction,chlorophyll a,optically complex waters,remote sensing,European Union Water Framework Directive (2000/60/EC),ecological status of water bodies,Copernicus,Sentinel-2 MultiSpectral Instrument
更新于2025-09-23 15:22:29
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Proximal fluorescence sensing of potassium responsive crops to develop improved predictions of biomass, yield and grain quality of wheat and barley
摘要： Precision nutrient management requires accurate assessment of crop nutrient status. This is common for assessing N status, but much less so for other nutrients. Because fluorescence can indicate crop stress, the robustness of different fluorescence indices was assessed to predict crop nutrient status (K, Mg and Ca). The hypothesis was that crop nutrition limitations, especially K, can be detected using fluorescence proximal sensing to quantify crop response with a high degree of spatial resolution. A factorial experiment was imposed with four treatment factors: crop, K fertilizer rate, lime and row management. The soil at the experimental site was K deficient and the crop variables showed significant treatment effects (e.g. yield, protein). Fluorescence sensing identified a significant positive K response for three chlorophyll related indices (SFR_G, SFR_R and CHL), but not for FLAV; while wheat was significantly different from barley. Using a k-fold cross-validation method promising predictive relationships were found. The strongest predictions were for SFR_R to predict crop biomass, for SFR_G to predict crop K content of inter-row wheat, for CHL to predict crop Ca content of inter-row wheat and for FLAV with barley grain protein in the windrow treatment. The fluorescence indices produced more significant crop variable predictions than measuring NDVI using an active sensor. This study illustrates the utility of fluorescence sensing to measure chlorophyll related signals for capturing the nutritional status of barley and wheat crops. These results show encouraging potential to rapidly detect crop nutrient status for non-N nutrients using fluorescence sensing.
关键词： Biomass,Wheat,Fluorescence indices,Chlorophyll,Grain quality prediction,Barley
更新于2025-09-23 15:22:29