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- 2017
- photosynthesis
- dry matter
- gas exchange
- chlorophyll content
- ozone layer.
- Agronomy
- University of Basilicata
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Monitoring of Fluorescence Characteristics of Satsuma Mandarin (Citrus unshiu Marc.) during the Maturation Period
摘要： Monitoring the maturation process of Satsuma mandarin (Citrus unshiu Marc.) by determining the soluble solids (SS) and acid content non-destructively is needed. Fluorescence components potentially offer such means of accessing fruit maturity characteristics in the orchard. The aim of this study was to determine the potential of ?uorescence spectroscopy for monitoring the stage of citrus maturity. Four major ?uorescent components in peel and/or ?esh were found including chlorophyll-a (excitation (Ex) 410 nm, emission (Em) 675 nm) and chlorophyll-b (Ex 460 nm, Em 650 nm),polymethoxy?avones (PMFs) (Ex 260 nm and 370 nm, Em 540 nm), coumarin (Ex 330 nm, Em 400 nm), and a tryptophan-like compound (Ex 260 nm, Em 330 nm). Our results indicated a signi?cant (R2 = 0.9554) logarithmic ratio between tryptophan-like compoundsExEm and chlorophyll-aExEm with the SS:acid ratio. Also, the log of the ratio of PMFs from the peel (ExExEm was signi?cantly correlated with the SS:acid ratio (R2 = 0.8207). While the latter correlation was not as strong as the former, it does demonstrate the opportunity to develop a non-destructive ?eld measurement of ?uorescent peel compounds as an indirect index of fruit maturity.
关键词： ?uorescence,soluble solid and acid ratio,tryptophan-like,chlorophyll-a,chlorophyll-b,polymethoxy?avones,maturity index
更新于2025-09-10 09:29:36
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A Fluorescence Sensor Capable of Real-Time Herbicide Effect Monitoring in Greenhouses and the Field
摘要： Herbicide resistant weeds need to be identi?ed early so that yield loss can be avoided by applying proper ?eld management strategies. A novel chlorophyll-?uorescence-imaging sensor has been developed to conduct real-time herbicide effect evaluation. In this research, greenhouse and ?eld experiments were conducted to calibrate the capability of the sensor in monitoring herbicide effects on different biotypes of two grass weeds (Alopecurus myosuroides, Apera spica-venti) in southwestern Germany. Herbicides with different modes of action were applied for the effect monitoring. Chlorophyll ?uorescence yield of the plants was measured 3–15 days after treatment (DAT) using the new ?uorescence sensor. Visual assessment of the weeds was carried out on 21 DAT. The results showed that the maximal PS II quantum yield (Fv/Fm) of herbicide sensitive weeds was signi?cantly lower than the values of resistant populations in 5 DAT. The new technology was capable of quickly identifying the herbicide’s effect on plants. It can be used to optimize management strategies to control herbicide resistant weeds.
关键词： real-time identi?cation,chlorophyll ?uorescence,herbicide effect
更新于2025-09-10 09:29:36
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Decadal Pattern of Spatial and Temporal Variability of Nitrate Along the Southwest Bay of Bengal Using Remote Sensing Techniques
摘要： The seasonal and interannual variability of sea surface nitrate was studied in the southwest Bay of Bengal. MODIS-Aqua-derived SST and chlorophyll data are used to develop seasonal nitrate maps for the period of 2002–2017. Seasonally developed nitrate images were validated for the year 2013 with corresponding in situ datasets, and the validation of this nitrate model provides the statistically signi?cant relationship for postmonsoon (R2 = 0.612), summer (R2 = 0.535), premonsoon (R2 = 0.554) and monsoon (R2 = 0.533) seasons. The seasonal SST, chlorophyll a, nitrate and wind speed images depict the clear seasonal pattern between the seasons without any abrupt increase or decrease in trend observed during all these years. This was also con?rmed by the Kruskal–Wallis one-way analysis of variance on ranks with a statistical signi?cance (P = \ 0.001) between the seasons. From the results, this is a clear indication that the nitrate concentration is under the natural control without any anthropogenic contaminations.
关键词： Paraboloid,Nitrate,Seasons,MODIS,Chlorophyll,SST
更新于2025-09-10 09:29:36
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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 - Detecting Rice Blast Disease Using Model Inverted Biochemical Variables from Close-Range Reflectance Imagery of Fresh Leaves
摘要： Rice blast is one of the most devastating crop diseases around the world. Although previous remote sensing studies have examined the spectral variation at leaf and canopy levels in response to disease severity levels, the non-imaging nature of their data makes it difficult to examine the spectral variation related to the disease within a leaf. This study proposes to monitor the spatial and temporal pattern of rice leaf blast on individual leaves with close-range imaging spectroscopy data. Hyperspectral images were acquired from diseased leaves at different infection stages. The image data were converted to reflectance cubes and then processed with a model inversion algorithm PROCWT to retrieve leaf biochemical variables. The biochemical maps were examined to investigate the within-leaf spatial variation and leaf-level temporal variation. Preliminary results demonstrated that the PROCWT algorithm could perform on reflectance image cubes. The retrieved chlorophyll maps exhibited a decline with infection stage and significant within-leaf spatial patterns in response to the disease.
关键词： Chlorophyll content,Hyperspectral imagery,Rice blast disease,PROCWT
更新于2025-09-10 09:29:36
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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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Interpretation of total phytoplankton and cyanobacteria fluorescence from cross-calibrated fluorometers, including sensitivity to turbidity and colored dissolved organic matter
摘要： In vivo pigment ?uorescence methods allow simple real-time detection and quanti?cation of freshwater algae and cyanobacteria. Available models are still limited to high-cost ?uorometers, validated for single instruments or individual water bodies, preventing data comparison between multiple instruments, and thus, restricting their use in large-scale monitoring programs. Moreover, few models include corrections for optical interference (water turbidity and colored dissolved organic matter, CDOM). In this study, we developed simple models to predict phytoplankton and cyanobacterial chlorophyll a (Chl a) concentrations based on Chl a and C-phycocyanin in vivo ?uorescence, using multiple low-cost handheld ?uorometers. We aimed to: (1) ?t models to mixed cyanobacterial and microalgal cultures; (2) cross-calibrate nine ?uorometers of the same brand and series; (3) correct the CDOM and turbidity effects; and (4) test the algorithms’ performance with natural samples. We achieved comparable results between nine instruments after the cross-calibration, allowing their simultaneous use. We obtained algorithms for total and cyanobacterial Chl a estimation. We developed parametric corrections to remove CDOM and turbidity interferences in the algorithms. Five sampling sites (from a lake, a stream, and an estuary) were used to test the algorithms using eight cross-calibrated ?uorometers. The models showed their best performance after CDOM and turbidity corrections (total Chl a: R2 = 0.99, RMSE = 7.8 μg Chl a L?1; cyanobacterial Chl a: R2 = 0.98, RMSE = 9.8 μg Chl a L?1). In summary, our models can quantify total phytoplankton and cyanobacterial Chl a in real time with multiple low-cost ?uorometers, allowing its implementation in large-scale monitoring programs.
关键词： CDOM,monitoring,turbidity,fluorescence,cyanobacteria,fluorometers,chlorophyll a,phytoplankton
更新于2025-09-10 09:29:36
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Nano Scale Potentiometric and Spectrophotometric Assays for 2,4-Dichlorophenoxyacetic Acid
摘要： The aim of this work was to investigate the ability of silicate wire ion selective electrode to measure 2,4 dichlorophenoxyacetic acid (2,4-D). The slope of the electrode was 56.2 mV decade -1 in the range from 10-6 to 10-2 M with lower limit of detection 8.3 × 10-7 M. The electrodes were successfully applied to determination of 2,4-D by separate and standard addition potentiometry. The electrode was used to detect the effect of pH and temperature on 2,4-D placed on baby watercress plant grown in the clay soil and the residue after five day from addition. Leaf chlorophylls quantity measured utilize spectrophotometric or colorimetric assay following extraction of pigments of watercress by ethanol. This work was carried at 286, 440, 662 nm. Beer’s law was obeyed in the concentration range of 2.21 mg/ml:2.21 μg/ml. The limits of detection were 2.21 μg/ml.
关键词： 2,4-Dichlorophenoxyacetic acid,Spectrophotometric,ion-selective electrodes,Wire,Chlorophyll,Potentiometric,Watercress
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
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Changes in the photosynthesis properties and photoprotection capacity in rice (Oryza sativa) grown under red, blue, or white light
摘要： Non-photochemical quenching (NPQ) of the excited state of chlorophyll a is a major photoprotective mechanism plants utilize to survive under high light. Here, we report the impact of long-term light quality treatment on photosynthetic properties, especially NPQ in rice. We used three LED-based light regimes, i.e., red (648–672 nm), blue (438–460 nm), and “warm” white light (529–624 nm), with the incident photon flux density of 300 μmol photons m?2 s?1, the difference in the absorbed photon flux densities by leaves grown under different light quality being less than 7%. Our results show that blue light, as compared to white light, induced a significant decrease in Fv/Fm, a decreased rate of reduction of P700+ after P700 was completely oxidized; furthermore, blue light also induced higher NPQ with an increased initial speed of NPQ induction, which corresponds to the qE component of NPQ, and a lower maximum quantum yield of PSII, i.e., Y(II). In contrast, rice grown under long-term red light showed decreased Y(II) and increased NPQ, but with no change in Fv/Fm. Furthermore, we found that rice grown under either blue or red light showed decreased transcript abundance of both catalase and ascorbate peroxidase, together with an increased H2O2 content, as compared to rice grown under white light. All these data suggest that even under a moderate incident light level, rice grown under blue or red light led to compromised antioxidant system, which contributed to decreased quantum yield of photosystem II and increased NPQ.
关键词： Non-photochemical quenching of the excited state of chlorophyll a,Effective quantum yield of PSII,Light quality,Quantum yield of regulated energy dissipation in PSII,Oryza sativa,Antioxidant system
更新于2025-09-10 09:29:36