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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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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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Remote sensing bio-control damage on aquatic invasive alien plant species
摘要： Aquatic Invasive Alien Plant (AIAP) species are a major threat to freshwater ecosystems, placing great strain on South Africa’s limited water resources. Bio-control programmes have been initiated in an effort to mitigate the negative environmental impacts associated with their presence in non-native areas. Remote sensing can be used as an effective tool to detect, map and monitor bio-control damage on AIAP species. This paper reconciles previous and current research concerning the application of remote sensing to detect and map bio-control damage on AIAP species. Initially, the spectral characteristics of bio-control damage are described. Thereafter, the potential of remote sensing chlorophyll content and chlorophyll fluorescence as pre-visual indicators of bio-control damage are reviewed and synthesised. The utility of multispectral and hyperspectral sensors for mapping different severities of bio-control damage are also discussed. Popular machine learning algorithms that offer operational potential to classify bio-control damage are proposed. This paper concludes with the challenges of remote sensing bio-control damage as well as proposes recommendations to guide future research to successfully detect and map bio-control damage on AIAP species.
关键词： machine learning algorithms,multispectral sensors,chlorophyll content,Aquatic Invasive Alien Plant (AIAP) species,chlorophyll fluorescence,hyperspectral sensors,Remote sensing,bio-control damage
更新于2025-09-23 15:19:57
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Optical properties of corals distort variable chlorophyll fluorescence measurements
摘要： Pulse amplitude modulated (PAM) fluorimetry is widely used in photobiological studies of corals, as it rapidly provides numerous photosynthetic parameters to assess coral ecophysiology. Coral optics studies have revealed the presence of light gradients in corals, which are strongly affected by light scattering in coral tissue and skeleton. We investigated whether coral optics affects variable chlorophyll fluorescence measurements and derived photosynthetic parameters by developing planar hydrogel slabs with immobilized microalgae and with bulk optical properties similar to those of different types of corals. Our results show that PAM-based measurements of photosynthetic parameters differed substantially between hydrogels with different degrees of light scattering but identical microalgal density, yielding deviations in apparent maximal electron transport rates by a factor of 2. Furthermore, system settings such as the measuring light intensity affected F0, Fm and Fv/Fm in hydrogels with identical light absorption but different degrees of light scattering. Likewise, differences in microalgal density affected variable chlorophyll fluorescence parameters, where higher algal densities led to greater Fv/Fm values and relative electron transport rates. These results have important implications for the use of variable chlorophyll fluorimetry in ecophysiological studies of coral stress and photosynthesis, as well as other optically dense systems such as plant tissue and biofilms.
关键词： light scattering,PAM fluorimetry,photosynthesis,hydrogels,variable chlorophyll fluorescence,coral optics
更新于2025-09-19 17:15:36
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Laser-induced fluorescence spectroscopy for early disease detection in grapefruit plants
摘要： Both biotic and abiotic stress causes considerable decrease in chlorophyll content in plant leaves which provide the means of early disease diagnosis. The emergence of disease affects the fluorescence of phenolic compounds and chlorophyll which have been appeared at 530, 686 and 735 nm. It has been found that the intensity of emission band of phenolic compounds at 530 nm increases and that of chlorophyll at 735 nm decreases with the onset of disease. Statistical analysis through principal component analysis (PCA) and partial least square regression (PLSR) has been performed which demonstrated the classification of apparently healthy leaf sites with diseased ones which provide the basis for the detection of disease at early stages. PLSR model was validated through the coefficient of determination (R2), standard error of prediction (SEP) and standard error of calibration (SEC) with the values 0.99, 0.394 and 0.401 which authenticated the model. The prediction accuracy of the model was evaluated through root mean square error in prediction (RMSEP) of 0.14 by predicting 22 unknown emission spectra of different leaf sites. Both PCA and PLSR models produced similar results and proved fluorescence spectroscopy as an excellent tool for early disease detection in plants.
关键词： Early disease diagnosis,Principal component analysis (PCA),Chlorophyll fluorescence,Partial least square regression (PLSR),Phenolic compounds
更新于2025-09-19 17:13:59
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High throughput procedure utilising chlorophyll fluorescence imaging to phenotype dynamic photosynthesis and photoprotection in leaves under controlled gaseous conditions
摘要： Background: As yields of major crops such as wheat (T. aestivum) have begun to plateau in recent years, there is growing pressure to efficiently phenotype large populations for traits associated with genetic advancement in yield. Photosynthesis encompasses a range of steady state and dynamic traits that are key targets for raising Radiation Use Efficiency (RUE), biomass production and grain yield in crops. Traditional methodologies to assess the full range of responses of photosynthesis, such a leaf gas exchange, are slow and limited to one leaf (or part of a leaf ) per instrument. Due to constraints imposed by time, equipment and plant size, photosynthetic data is often collected at one or two phenological stages and in response to limited environmental conditions. Results: Here we describe a high throughput procedure utilising chlorophyll fluorescence imaging to phenotype dynamic photosynthesis and photoprotection in excised leaves under controlled gaseous conditions. When measured throughout the day, no significant differences (P > 0.081) were observed between the responses of excised and intact leaves. Using excised leaves, the response of three cultivars of T. aestivum to a user—defined dynamic lighting regime was examined. Cultivar specific differences were observed for maximum PSII efficiency (Fv′/Fm′—P < 0.01) and PSII operating efficiency (Fq′/Fm′—P < 0.04) under both low and high light. In addition, the rate of induction and relaxation of non-photochemical quenching (NPQ) was also cultivar specific. A specialised imaging chamber was designed and built in-house to maintain gaseous conditions around excised leaf sections. The purpose of this is to manipulate electron sinks such as photorespiration. The stability of carbon dioxide (CO2) and oxygen (O2) was monitored inside the chambers and found to be within ± 4.5% and ± 1% of the mean respectively. To test the chamber, T. aestivum ‘Pavon76’ leaf sections were measured under at 20 and 200 mmol mol?1 O2 and ambient [CO2] during a light response curve. The Fv′/Fm′was significantly higher (P < 0.05) under low [O2] for the majority of light intensities while values of NPQ and the proportion of open PSII reaction centers (qP) were significantly lower under > 130 μmol m?2 s?1 PPFD. Conclusions: Here we demonstrate the development of a high-throughput (> 500 samples day?1) method for phenotyping photosynthetic and photo-protective parameters in a dynamic light environment. The technique exploits chlorophyll fluorescence imaging in a specifically designed chamber, enabling controlled gaseous environment around leaf sections. In addition, we have demonstrated that leaf sections do not different from intact plant material even > 3 h after sampling, thus enabling transportation of material of interest from the field to this laboratory based platform. The methodologies described here allow rapid, custom screening of field material for variation in photosynthetic processes.
关键词： Dynamic,Imaging,Phenotyping,Wheat,Photo-protection,Photosynthesis,Chlorophyll fluorescence
更新于2025-09-16 10:30:52
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Mode-locked Tm-doped fiber laser with large modulation depth ReS <sub/>1.02</sub> Se <sub/>0.98</sub> nanosheet saturable absorber
摘要： Microcystis blooms and their associated microcystins pose a significant health risk to humans. Microcystis normally occurs as colonies in eutrophic water bodies, and its physiological tolerance to algaecides is dissimilar to that of unicellular forms. However, the differences of physiological response to algaecides between unicellular and colonial Microcystis have been poorly explored. The current study investigated the effects of hexane extract of Acorus calamus rhizome (HEACR) on the physiological and photosynthetic mechanisms of unicellular and colonial M. aeruginosa in the laboratory. We analyzed the cell density, reactive oxygen species (ROS) level, malonaldehyde (MDA) content, photosynthetic pigments, capsular polysaccharide (CPS), and photosystem (PS II) parameters of the two morphological forms of Microcystis. Our results show that HEACR suppresses the growth of both unicellular and colonial M. aeruginosa, increases the intracellular ROS level and cause lipid peroxidation, as well as exerting a detrimental effect on chlorophyll a (chl a) content and photosynthetic efficiency. Almost 100% inhibition was observed for unicellular and colonial M. aeruginosa after 3 d exposure to 50 and 100 mg L?1 HEACR, respectively. The ROS level increase, MDA accumulation, the chl a decrease and carotenoid increase in unicellular M. aeruginosa were all more obvious than that in colonial cells. The fall in photosynthetic efficiency of unicellular M. aeruginosa were also more significant than that of colonial cells. After 3d exposure, the maximum quantum yield of PS II photochemistry (Fv/Fm), effective quantum yield of PS II photochemistry (Fv’/Fm’) and effective quantum yield of photochemical energy conversion in PS II (YII) of unicellular M. aeruginosa was almost totally inhibited by 20 mg L?1 HEACR, while the Fv/Fm, Fv’/Fm’ and YII of colonial M. aeruginosa decreased by 43%, 26% and 66% for 100 mg L?1 of HEACR, respectively. Comparing the two morphological forms of Microcystis, colonies show a greater increase in CPS level to more effectively resist the stress of HEACR and to mitigate ROS generation thereby better defending against oxidative damage. Furthermore, colonial M. aeruginosa shows better photoprotection ability than the unicellular form when exposed to HEACR. The colonies also sustain their maximum electron transport rate, increase their tolerance to strong light, and maintain a higher ability to disperse excess energy. These results demonstrated that HEACR can significantly interfere with the growth and physiological processes of both unicellular and colonial M. aeruginosa, but that colonial M. aeruginosa has a greater ability to adjust physiological tolerance to resist the stresses of HEACR.
关键词： Reactive oxygen species,Acorus calamusrhizome extract,Microcystis aeruginosa,Physiological tolerance,Capsular polysaccharide,Chlorophyll fluorescence parameters
更新于2025-09-11 14:15:04
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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 - Comparison of Four Different Sun-Induced Chlorophyll Fluorescence Retrieval Algorithms Using Simulated and Field-Measured Data
摘要： Up to now, there are four widely used retrieval algorithms for retrieving sun-induced chlorophyll fluorescence (SIF) from plant photosynthesis: the standard FLD method (FLD), the modified FLD (3FLD), the improved FLD (iFLD) and the spectral fitting method (SFM). This paper attempts to compare the four different sun-induced chlorophyll fluorescence retrieval algorithms using simulated and field-measured data. The results show that the SFM and the iFLD methods provide more accurate SIF estimations with root mean square error (RMSE) less than 0.1, using the simulated data. However, when the field-measured data are used, the SFM method is better and the iFLD method becomes unstable, which suggests that the SFM method is appropriate to retrieve SIF from field data measured using a spectrometer instrument with spectral resolution lower than 1nm.
关键词： spectral fitting method (SFM),fraunhofer line discrimination (FLD),Sun-induced chlorophyll fluorescence (SIF),the improved FLD (iFLD),the modified FLD (3FLD)
更新于2025-09-10 09:29:36
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[American Society of Agricultural and Biological Engineers 2017 Spokane, Washington July 16 - July 19, 2017 - ()] 2017 Spokane, Washington July 16 - July 19, 2017 - <i>Phenotyping of Arabidopsis for drought stress response using kinetic chlorophyll fluorescence imaging</i>
摘要： Drought stress is one of the major concerns in global agricultural production. Developing an efficient phenotyping technology can bridge the knowledge gap between the plant phenotype and genotype, which can promote the progress of breeding for drought tolerant accessions and provide economic benefits for the producers and consumers. This research was aimed to investigate the plant phenotyping for drought stress responses of two different genotypes of Arabidopsis using chlorophyll fluorescence imaging. 59 treatment groups (three plants for each group) of each genotype were withholding being watered for 8 days as the drought stress treatment, and the other 59 groups considered as control were regularly watered with 6 ml 1% nutrient solution every day. The kinetic chlorophyll fluorescence images of the drought treatment groups and the control groups were acquired at day 1, 3, 5, 7 and 8 after the drought stress treatment started. The conventional chlorophyll fluorescence parameters and the leaf area index were then extracted from the images. In addition, associated morphological and physiological parameters were also assayed. To construct combinatorial images, the sequential forward selection (SFS) algorithm was used to select the maximum contrast images between two genotypes and the linear discriminant analysis (LDA) was used to build combinatorial images. Finally, combinatorial images were analyzed, indicating combinatorial images are valuable in drought stress studies. Above all, the study showed that AQ and osca1 presented different drought stress responses during the treatment period based on the conventional chlorophyll parameters and combinatorial images.
关键词： drought stress,Arabidopsis,plant phenotyping,combinatorial imaging,Chlorophyll fluorescence imaging
更新于2025-09-10 09:29:36
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Compensation of Oxygen Transmittance Effects for Proximal Sensing Retrieval of Canopy–Leaving Sun–Induced Chlorophyll Fluorescence
摘要： Estimates of Sun–Induced vegetation chlorophyll Fluorescence (SIF) using remote sensing techniques are commonly determined by exploiting solar and/or telluric absorption features. When SIF is retrieved in the strong oxygen (O2) absorption features, atmospheric effects must always be compensated. Whereas correction of atmospheric effects is a standard airborne or satellite data processing step, there is no consensus regarding whether it is required for SIF proximal–sensing measurements nor what is the best strategy to be followed. Thus, by using simulated data, this work provides a comprehensive analysis about how atmospheric effects impact SIF estimations on proximal sensing, regarding: (1) the sensor height above the vegetated canopy; (2) the SIF retrieval technique used, e.g., Fraunhofer Line Discriminator (FLD) family or Spectral Fitting Methods (SFM); and (3) the instrument's spectral resolution. We demonstrate that for proximal–sensing scenarios compensating for atmospheric effects by simply introducing the O2 transmittance function into the FLD or SFM formulations improves SIF estimations. However, these simplistic corrections still lead to inaccurate SIF estimations due to the multiplication of spectrally convolved atmospheric transfer functions with absorption features. Consequently, a more rigorous oxygen compensation strategy is proposed and assessed by following a classic airborne atmospheric correction scheme adapted to proximal sensing. This approach allows compensating for the O2 absorption effects and, at the same time, convolving the high spectral resolution data according to the corresponding Instrumental Spectral Response Function (ISRF) through the use of an atmospheric radiative transfer model. Finally, due to the key role of O2 absorption on the evaluated proximal–sensing SIF retrieval strategies, its dependency on surface pressure (p) and air temperature (T) was also assessed. As an example, we combined simulated spectral data with p and T measurements obtained for a one–year period in the Hyyti?l? Forestry Field Station in Finland. Of importance hereby is that seasonal dynamics in terms of T and p, if not appropriately considered as part of the retrieval strategy, can result in erroneous SIF seasonal trends that mimic those of known dynamics for temperature–dependent physiological responses of vegetation.
关键词： fraunhofer line discriminator (FLD),air temperature,spectral fitting method (SFM),atmospheric pressure,proximal sensing,O2 transmittance,sun–induced chlorophyll fluorescence (SIF)
更新于2025-09-10 09:29:36