Página 1 dos resultados de 1382 itens digitais encontrados em 0.007 segundos

Strong quenching of chlorophyll fluorescence in the desiccated state in three poikilohydric and homoiochlorophyllous moss species indicates photo-oxidative protection on highly light-exposed rocks of a tropical inselberg

LUETTGE, Ulrich; MEIRELLES, Sergio T.; MATTOS, Eduardo Arcoverde de
Fonte: ELSEVIER GMBH, URBAN & FISCHER VERLAG Publicador: ELSEVIER GMBH, URBAN & FISCHER VERLAG
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.37%
The three poikilophydric and homoiochlorophyllous moss species Campylopus savannarum (C. Muell.) Mitt., Racocarpus fontinaloides (C. Muell.) Par. and Ptychomitrium vaginatum Besch. grow on sun-exposed rocks of a tropical inselberg in Brazil subject to regular drying and wetting cycles. Effective photo-oxidative protection in the light-adapted desiccated state in all three species is achieved by a reduction of ground chlorophyll fluorescence, F, to almost zero. Upon rewatering, the kinetics of the recovery of F in air dry cushions to higher values is very fast in the first 5min, but more than 80min are needed until an equilibrium is reached gradually. The kinetics were not different between the three species. The three moss species, have a distinct niche occupation and form a characteristic zonation around soil vegetation islands on the rock outcrops, where C. savannarum and R. fontinaloides form an inner and outer belt, respectively, around vegetation islands and P vaginatum occurs as small isolated cushions on bare rock. However, they were not distinguished by the reduction of F in the dry state and the rewetting recovery kinetics and only slightly different in their photosynthetic capacity. Stable isotope ratios (delta C-13, delta N-15) indicate that liquid films of water limiting diffusion of CO2 are important in determining carbon acquisition and suggest that limitation of CO2 fixation by water films must be more pronounced over time in P vaginatum than in the latter species. This is determined by both the micro site occupied and the form of the moss cushions. (c) 2007 Elsevier GmbH. All rights reserved.

The effects of UV radiation on photosynthesis estimated as chlorophyll fluorescence in Zygnemopsis decussata (Chlorophyta) growing in a high mountain lake (Sierra Nevada, Southern Spain)

FIGUEROA, Felix L.; KORBEE, Nathalie; CARRILLO, Presentacion; MEDINA-SANCHEZ, Juan Manuel; MATA, Mayte; BONOMI, Jose; SANCHEZ-CASTILLO, Pedro M.
Fonte: CNR IST ITALIANO IDROBIOLOGIA Publicador: CNR IST ITALIANO IDROBIOLOGIA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.37%
The effect of increased UV radiation on photosynthesis estimated as in vivo chlorophyll fluorescence i.e. optimal quantum yield (F(v)/F(m)) and electron transport rate (ETR) in the green filamentous alga Zygnemopsis decussata (Streptophyta, Zygnematales) growing in the high mountain lake ""La Caldera"" (Sierra Nevada, Spain) at 3050 m altitude was evaluated. Two sets of in situ experiments were conducted: (1) On July 2006, F(v)/F(m) was measured throughout the day at different depths (0.1, 0.25, 0.5 and 1 m) and in the afternoon. ETR and phenolic compounds were determined. In addition, in order to analyze the effect of UV radiation, F(v)/F(m) was determined in algae incubated for 3 days at 0.5m under three different light treatments: PAR+UVA+UVB (PAB). PAR+UVA (PA) and PAR (P). (2) On August 2007, F(v)/F(m) was determined under PAB, PA and P treatments and desiccation/rehydration conditions. F(v)/F(m) decreased in algae growing in surface waters (0.1 m) but also at 1 m depth compared to that at 0.5 in depth. The decrease of F(v)/F(m) at noon due to photoinhibition was small (less than 10%) except in algae growing at 1 m depth (44%). The maximal electron transport rate was 3.5-5 times higher in algae growing at 0.25-0.5 m respectively than that at 0.1 and 1 m depth. These results are related to the accumulation of phenolic compounds: i.e. the algae at 0.25-0.5 in presentedrespectively about a 3-5 times higher concentration of phenolic compounds than that of algae at 0.1-1 m depth. The protection mechanisms seem to be stimulated by UVB radiation...

Chlorophyll fluorescence as a marker for herbicide mechanisms of action

Dayan, Franck E.; Zaccaro, Maria Leticia de M.
Fonte: Academic Press Inc. Elsevier B.V. Publicador: Academic Press Inc. Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 189-197
ENG
Relevância na Pesquisa
66.55%
Photosynthesis is the single most important source of 02 and organic chemical energy necessary to support all non-autotrophic life forms. Plants compartmentalize this elaborate biochemical process within chloroplasts in order to safely harness the power of solar energy and convert it into usable chemical units. Stresses (biotic or abiotic) that challenge the integrity of the plant cell are likely to affect photosynthesis and alter chlorophyll fluorescence. A simple three-step assay was developed to test selected herbicides representative of the known herbicide mechanisms of action and a number of natural phytotoxins to determine their effect on photosynthesis as measured by chlorophyll fluorescence. The most active compounds were those interacting directly with photosynthesis (inhibitors of photosystem I and II), those inhibiting carotenoid synthesis, and those with mechanisms of action generating reactive oxygen species and lipid peroxidation (uncouplers and inhibitors of protoporphyrinogen oxidase). Other active compounds targeted lipids (very-long-chain fatty acid synthase and removal of cuticular waxes). Therefore, induced chlorophyll fluorescence is a good biomarker to help identify certain herbicide modes of action and their dependence on light for bioactivity. Published by Elsevier B.V.

Shelf-life of ripening ‘rocha’ pear: effects of the orchard irrgation regIme on qualityI and fluorescence parameters

Elias, Elsa; Silva, Anabela Bernardes da; Antunes, Rosário; Silva, Jorge Marques da
Fonte: Universidade do Algarve Publicador: Universidade do Algarve
Tipo: Parte de Livro
Publicado em //2010 ENG
Relevância na Pesquisa
56.65%
Proceedings of the International Conference “Environmentally friendly and safe technologies for quality of fruit and vegetables”, held in Universidade do Algarve, Faro,Portugal, on January 14-16, 2009. This Conference was a join activity with COST Action 924; The effect of the orchard irrigation regime on the on-shelf ripening of Pyrus communis L. var. ‘Rocha’ fruit was studied and the use of chlorophyll a fluorescence as a tool to assess the maturation of fruit was evaluated. Minimal (Fo) and maximal (Fm) fluorescence and maximal photochemical efficiency of PSII reaction centers (Fv/Fm) were measured in pear grown in irrigated (Ir) and non-irrigated (NIr) orchards and stored for two months in cold under normal atmospheric conditions, after which fruits were removed from the refrigerated chambers and held at room temperature (approx. 20 ºC) for 14 days (d). Measurements were made on the day of removal from refrigerated storage (t=0) and after 4, 7, 10 and 14 d at 20 ºC. Total chlorophyll content (Chl a+b) of pears skin was measured as well as the pulp firmness and the total content of soluble solids (SSC). At 0 d at room temperature, Ir fruit, although with a lower chlorophyll content, was firmer than NIr fruit but after 14 d at room temperature no differences were observed between them. No significant differences were generally observed in SSC either between Ir and NIr fruit or during ripening. All fluorescence parameters decreased in Ir and NIr fruit...

Chlorophyll fluorescence parameters in populations of two legume trees: Stryphnodendron adstringens (Mart.) Coville (Mimosoideae) and Cassia ferruginea (Schrad.) Schrad. ex DC. (Caesalpinoideae)

Lemos Filho,José P.; Goulart,Maíra F.; Lovato,Maria B.
Fonte: Sociedade Botânica de São Paulo Publicador: Sociedade Botânica de São Paulo
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2004 EN
Relevância na Pesquisa
66.51%
The aim of this study was to investigate the photosynthetic performance in populations of two legume tree species, Stryphnodendron adstringens (Mimosoideae), typical from Cerrado, and Cassia ferruginea (Caesalpinoideae) from the Atlantic Rain Forest. The photosynthetic traits were assessed by measures of chlorophyll fluorescence in progenies of naturally pollinated plants from three populations of S. adstringens and a population of C. ferruginea. Plants of S. adstringens growing under similar conditions of C. ferruginea plants demanded higher light values for photosynthesis saturation, 600 µmol.m-2.s-1 and 350 µmol.m-2.s-1 respectively, and showed higher intrinsic photosynthetic efficiency of photosystem II, Fv/Fm of 0.814 versus 0.783 in C. ferruginea. The highest values of Fv/Fm observed in S. adstringens can explain the highest electron transport rates (ETR) obtained for this species. No significant differences were found among progenies from different C. ferruginea trees nor among populations of S. adstringens, and only in few cases, variation among progenies within populations were found for S. adstringens plants. The fact that fluorescence parameters distinguished species but not populations or most of progenies may be related to low intraspecific genetic variation of these chlorophyll fluorescence traits or due to lack of expression on genetic differences in plants under no stressful conditions.

Chlorophyll fluorescence of the testa of Brassica oleracea seeds as an indicator of seed maturity and seed quality

Jalink,H.; Frandas,A.; Schoor,R. van der; Bino,J.B.
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/1998 EN
Relevância na Pesquisa
66.73%
Chlorophyll fluorescence of the testa of seeds is proposed as a non-invasive method for the determination of maturity and quality of seeds. In this study cabbage seeds (Brassica oleracea) were sorted individually based on the chlorophyll fluorescence signals into four subsamples labeled with respect to their chlorophyll fluorescence signal (low, medium, high and very high). The results show that the magnitude of the chlorophyll fluorescence signal was inversely related to the quality of the seeds, expressed as germination %, normal seedling %, germination rate (T50) and uniformity of germination (T75-T25). The seed lot could be improved from 90 to 97% normal seedlings by sorting out 13% of the seeds with very high chlorophyll fluorescence signals. Advantages of the chlorophyll fluorescence method for sorting seeds are the high sensitivity, the method being fully non-destructive, the high speed at which the fluorescence is generated and measured and the specificity for only chlorophyll. Other pigments or substances which can influence seed colour but do not fluoresce at the specific wavelengths of excitation and emission of chlorophyll, will not contribute to the fluorescence signal. These characteristics make chlorophyll fluorescence highly suitable as a new sorting technique.

Photosynthetic response of Amphibolis antarctica and Posidonia australis to temperature and desiccation using chlorophyll fluorescence

Seddon, Stephanie; Cheshire, A. C.
Fonte: Inter-Research Publicador: Inter-Research
Tipo: Artigo de Revista Científica
Publicado em //2001 EN
Relevância na Pesquisa
66.37%
Exposure to desiccation during heat wave conditions (≥35°C) is considered the most likely cause of a sudden dieback of 12700 ha of intertidal and shallow subtidal seagrasses along 95 km of coast in Spencer Gulf, South Australia. To investigat this hypothesis experiments in a constant environment (CE) room were designed to test the tolerances of 2 shallow subtidal species, Amphibolis antarctica and Posidonia australis, to desiccation for a range of temperatures and exposure times. The first experiment compared the effects of increasing exposure time (15, 30, 45, 60, 80 and 100 min) on photosynthetic efficiency at a relatively mild summer temperature (CE room set to 24°C). The second experiment compared the effects of increasing temperature (CE room temperature set to 18, 24, 28 or 32°C) and exposure time (0, 20 and 60 min). Photosynthetic efficiency, damage and extent of recovery were determined by chlorophyll fluorescence measured using a pulse amplitude modulated fluorometer. The ability of both species to recover from desiccation decreased at higher temperatures and longer exposure time, with P. australis more susceptible to desiccation than A. antarctica. The results indicate that higher temperatures alone did not significantly affect photosynthetic efficiency for either species. Four main responses for maximal quantum yield over a time series were apparent: (1) no difference from controls...

Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap

Ribeiro, Rafael Vasconcelos; Souza, Gustavo Maia; Manzatto, Angelo Gilberto; Machado, Eduardo Caruso; Oliveira, Ricardo Ferraz de
Fonte: Sociedade de Investigações Florestais Publicador: Sociedade de Investigações Florestais
Tipo: Artigo de Revista Científica Formato: 21-27
ENG
Relevância na Pesquisa
66.51%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); A caracterização dos diferentes grupos ecológicos envolvidos nos processos de formação/sucessão florestal é ainda pouco precisa. Para melhor distinção das classes sucessionais deve-se levar em consideração aspectos ecofisiológicos, como a capacidade de aproveitamento da energia luminosa. O objetivo deste trabalho foi acessar a emissão da fluorescência da clorofila de espécies arbóreas tropicais crescendo em uma clareira de floresta semidecídua. Foram selecionadas três espécies de diferentes grupos ecológicos: Croton floribundus Spreng. (pioneira, P), Astronium graveolens Jacq. (secundária inicial, Si) e Esenbeckia febrifuga A. Juss. (secundária tardia, St). A eficiência quântica potencial (Fv/Fm) e efetiva (deltaF/Fm') do fotossistema II, a taxa aparente de transporte de elétrons (ETR) e os coeficientes de extinção fotoquímica (qP) e não-fotoquímica (qN) da fluorescência da clorofila foram avaliados, utilizando um fluorômetro modulado, entre 7h30 e 11h. Os valores de Fv/Fm permaneceram constantes em St, diminuindo em P e Si a partir das 9h30, indicando a ocorrência de fotoinibição. Entretanto...

Chlorophyll fluorescence of tropical tree species in a semi-deciduous forest gap

Ribeiro,Rafael Vasconcelos; Souza,Gustavo Maia; Manzatto,Angelo Gilberto; Machado,Eduardo Caruso; Oliveira,Ricardo Ferraz de
Fonte: Sociedade de Investigações Florestais Publicador: Sociedade de Investigações Florestais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2004 EN
Relevância na Pesquisa
66.51%
The characterization of different ecological groups in a forest formation/succession is unclear. To better define the different successional classes, we have to consider ecophysiological aspects, such as the capacity to use or dissipate the light energy available. The main objective of this work was to assess the chlorophyll fluorescence emission of tropical tree species growing in a gap of a semi-deciduous forest. Three species of different ecological groups were selected: Croton floribundus Spreng. (pioneer, P), Astronium graveolens Jacq. (early secondary, Si), and Esenbeckia febrifuga A. Juss. (late secondary, St). The potential (Fv/Fm) and effective (deltaF/Fm') quantum efficiency of photosystem II, apparent electron transport rate (ETR), non-photochemical (qN) and photochemical (qP) quenching of fluorescence were evaluated, using a modulated fluorometer, between 7:30 and 11:00 h. Values of Fv/Fm remained constant in St, decreasing in P and Si after 9:30 h, indicating the occurrence of photoinhibition. Concerning the measurements taken under light conditions (deltaF/Fm', ETR, qP and qN), P and Si showed better photochemical performance, i.e., values of deltaF/Fm', ETR and qP were higher than St when light intensity was increased. Values of qN indicated that P and Si had an increasing tendency of dissipating the excess of energy absorbed by the leaf...

Chlorophyll Fluorescence Detection with a High-Spectral Resolution Spectrometer through in-filling of the O2-A band as function of Water Stress in Olive Trees

Zarco-Tejada, Pablo J.; Pérez-Priego, O.; Sepulcre-Cantó, G.; Miller, J. R.; Fereres Castiel, Elías
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Comunicación de congreso Formato: 685368 bytes; application/pdf
ENG
Relevância na Pesquisa
56.59%
2nd International Workshop on Remote Sensing of Vegetation Fluorescence, 17-19 Nov. 2004, Montreal, Canada; A high spectral resolution spectrometer of 0.065 nm FWHM in the 680-770 nm range was used for collecting spectral measurements in an orchard of olive trees in Spain under 3 different water stress treatments. The measurements were conducted as part of validation efforts for the FluorMOD project funded by the European Space Agency (ESA) to advance the science of vegetation fluorescence simulation. Diurnal steadystate chlorophyll fluorescence was measured from leaves in the field during summer 2004 using the PAM-2100 fluorometer to study the effects of water stress on chlorophyll fluorescence. Water potential, photosynthesis, and stomatal conductance on trees were also measured in a weekly basis to track the effects of water stress on the tree status and functioning. Infrared Apogee sensors were placed on top of the trees for diurnal thermal data collection, studying the effects of water stress on the tree temperature as an indicator of stress. The Ocean Optics HR-2000 spectrometer was used to measure irradiance and radiance spectra from above tree crowns under different stress conditions. The spectral measurements of irradiance with a cosine corrector and crown radiance with bare fibre were acquired from a pole 7 m in height to collect nadir radiance from the top of tree crowns. Analysis in the red edge covering the 680-770 nm range enabled the study of the chlorophyll fluorescence in-filling in the O2-A band at 760 nm. Results of the spectral analysis and simulation using the FluorMOD radiative transfer model demonstrate that water stress effects on steady-state fluorescence are detectable at the tree level in the O2-A band from reflectance spectra due to the in-filling effects.; The development of the FluorMODgui interface has been carried out in the frame of the ESA-project Development of a Vegetation Fluorescence Canopy Model...

Detection of chlorophyll fluorescence in vegetation from airborne hyperspectral CASI imagery in the red edge spectral region

Zarco-Tejada, Pablo J.; Miller, J. R.; Haboudane, D.; Tremblay, N.; Apostol, S.
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Comunicación de congreso Formato: 259279 bytes; application/pdf
ENG
Relevância na Pesquisa
66.53%
2003 - International Geoscience and Remote Sensing Symposium, IGARSS'03, pp. 598- 600 Vol.1, Toulouse (France), 21-25/7/2004; This work provides a description of the investigations conducted to assess the detection of chlorophyll fluorescence from hyperspectral CASI data. The viability of retrieval of solarinduced fluorescence through airborne imaging spectrometer measurements of radiance of targets under natural illumination is studied. A method based on in-filling of fluorescence signals in atmospheric oxygen absorption lines is applied to study sites of corn crop grown under different stress conditions due to variations in nitrogen treatment. Results of the relationships found between measurements of laser-induced fluorescence and chlorophyll concentration at the ground level with the in-filling of the 762 nm oxygen band and optical indices calculated from CASI imagery R685/R655, derivative D730/D706, and the doublepeak derivative reflectance index DPi (D688·D710 )/D697 2 are presented.; Peer reviewed

FluorMODgui V3.0: A graphic user interface for the spectral simulation of leaf and canopy chlorophyll fluorescence

Zarco-Tejada, Pablo J.; Miller, J. R.; Pedrós, R.; Verhoef, W.; Berger, M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 4085 bytes; image/gif
ENG
Relevância na Pesquisa
56.6%
The FluorMODgui Graphic User Interface (GUI) software package developed within the frame of the FluorMOD project Development of a Vegetation Fluorescence Canopy Model is presented in this manuscript. The FluorMOD project was launched in 2002 by the European Space Agency (ESA) to advance the science of vegetation fluorescence simulation through the development and integration of leaf and canopy fluorescence models based on physical methods. The design of airborne or space missions dedicated to the measurement of solar-induced chlorophyll fluorescence using remote-sensing instruments require physical methods for quantitative feasibility analysis and sensor specification studies. The FluorMODgui model developed as part of this project is designed to simulate the effects of chlorophyll fluorescence at leaf and canopy levels using atmospheric inputs, running the leaf model, FluorMODleaf, and the canopy model, FluorSAIL, independently, through a coupling scheme, and by a multiple iteration protocol to simulate changes in the viewing geometry and atmospheric characteristics. Inputs for the FluorMODleaf model are the number of leaf layers, chlorophyll a+b content, water equivalent thickness, dry matter content, fluorescence quantum efficiency...

Detection of Water Stress in Orchard Trees with a High-Resolution Spectrometer through Chlorophyll Fluorescence in-filling of the O2-A band

Pérez-Priego, O.; Zarco-Tejada, Pablo J.; Miller, J. R.; Sepulcre-Cantó, G.; Fereres Castiel, Elías
Fonte: Institute of Electrical and Electronics Engineers Publicador: Institute of Electrical and Electronics Engineers
Tipo: Artículo Formato: 4085 bytes; image/gif
ENG
Relevância na Pesquisa
66.66%
A high spectral resolution spectrometer with 0.065-nm full-width half-maximum was used for collecting spectral measurements in an orchard field under three water stress treatments. The study was part of the FluorMOD project funded by the European Space Agency to develop a leaf-canopy reflectance model to simulate the effects of fluorescence. Water deficit protocols generated a gradient in solar-induced chlorophyll fluorescence emission and tree physiological measures. Diurnal steady-state chlorophyll fluorescence was measured from leaves in the field between June and November 2004 using the PAM-2100 fluorometer to study the effects of water stress on chlorophyll fluorescence. Spectral measurements of downwelling irradiance and upwelling crown radiance were conducted with the narrow-band spectrometer, enabling the canopy reflectance to be obtained at subnanometer spectral resolution and permitting the evaluation of the fluorescence in-filling effects on reflectance in trees under water stress conditions. Diurnal and seasonal measurements showed consistently lower steady-state fluorescence (Ft) and quantum yield F Fm in water-stressed trees, yielding mean values of Ft = 038 (well-irrigated) and Ft = 0 21 (water-stressed trees). The agreement between Ft and water potential showed that steady-state fluorescence could be used to detect differences in water stress levels...

Chlorophyll Fluorescence effects on Vegetation Apparent Reflectance: I. Leaf-level Measurements and Model Simulation

Zarco-Tejada, Pablo J.; Miller, J. R.; Mohammed, G. H.; Noland, T. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 4085 bytes; image/gif
ENG
Relevância na Pesquisa
66.63%
Results from a series of laboratory measurements of spectral reflectance and transmittance of individual leaves and from a modeling study are presented which demonstrate that effects of natural chlorophyll fluorescence (CF) are observable in the red edge spectral region. Measurements have been made with a Li-Cor Model 1800 integrating sphere apparatus coupled to an Ocean Optics Model ST1000 fiber spectrometer in which the same leaves are illuminated alternately with and without fluorescence-exciting radiation in order to separate the fluorescence emission component from the reflectance spectrum. The resulting difference spectrum is shown experimentally to be consistent with a fluorescence signature imposed on the inherent leaf reflectance signature. A study of the diurnal change in leaf reflectance spectra, combined with fluorescence measurements with the PAM-2000 Fluorometer, show that the difference spectra are consistent with observed diurnal changes in steady-state fluorescence. In addition, the time decay in the difference signature from repetitive leaf spectral reflectance measurements is seen to be consistent with the time decay of the leaf fluorescence signal (Kautsky effect) of dark-adapted leaves. The expected effects of chlorophyll fluorescence emission on the apparent spectral reflectance from a single leaf are also simulated theoretically using the doubling radiative transfer method. These modeling results demonstrate that the laboratory observations of a difference spectrum with broad peak at about 750 nm and a much smaller peak near 690 nm are in agreement with theory. Model simulation shows that chlorophyll pigment and fluorescence each affect indices that are being used in optical remote sensing to characterize pigment levels and stress in vegetation canopies. Implications for high spectral resolution remote sensing of forest canopies are presented in a companion paper.; Peer reviewed

Chlorophyll Fluorescence effects on Vegetation Apparent Reflectance: II. Laboratory and Airborne Canopy-Level Measurements with Hyperspectral Data

Zarco-Tejada, Pablo J.; Miller, J. R.; Mohammed, G. H.; Noland, T. L.; Sampson, P. H.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 4085 bytes; image/gif
ENG
Relevância na Pesquisa
66.7%
Relationships found between Compact Airborne Spectrographic Imager (CASI) hyperspectral canopy reflectance measurements at laboratory and field levels with PAM-2000 chlorophyll fluorescence data are presented. This is a continuation of the paper where relationships at the leaf level between leaf reflectance and chlorophyll fluorescence were found and demonstrated to be consistent with theory using the Fluorescence-Reflectance-Transmittance (FRT) model. Experiments using the hyperspectral CASI sensor in the laboratory to observe a canopy of maple seedlings are performed as an intermediate step to demonstrate the link between the results at leaf-level and the CASI field canopy levels. Scene observations of the seedlings utilizing a long-pass blocking filter showed that apparent canopy reflectance in the laboratory is affected by changes in fluorescence emissions. A laboratory experiment on seedlings subjected to diurnally induced change shows the strong link between CASI canopy reflectance optical indices in the 680–690-nm region and Fv/Fm dark-adapted chlorophyll fluorescence. Stressed and healthy maple seedlings are used to demonstrate the use of optical indices calculated from the 680–690-nm spectral region to track changes in steady-state fluorescence: the curvature index R6832/(R675·R691) and the R685/R655 ratio calculated from the canopy reflectance are related to leaf-measured Ft...

Estimation of Chlorophyll Fluorescence under Natural Illumination from Hyperspectral Data

Zarco-Tejada, Pablo J.; Miller, J. R.; Mohammed, G. H.; Noland, T. L.; Sampson, P. H.
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Comunicación de congreso Formato: 160470 bytes; application/pdf
ENG
Relevância na Pesquisa
66.48%
Presented at the Second EARSeL Workshop on Imaging Spectroscopy, Enschede (Holland), 11th-13th July 2000.; This paper reports a series of laboratory and field measurements of spectral reflectance under artificial and natural light conditions which demonstrate that effects of natural chlorophyll fluorescence are observable in the reflectance red edge spectral region. These are results from the progress made to link physiologically-based indicators to optical indices from hyperspectral remote sensing in the Bioindicators of Forest Sustainability Project. This study is carried out on twelve sites of Acer saccharum M. in the Algoma Region, Ontario (Canada), where field measurements, laboratory-simulation experiments, and hyperspectral CASI imagery have been carried out in 1997, 1998, 1999 and 2000 campaigns. Leaf samples from the study sites have been used for reflectance and transmittance measurements with the Li-Cor Model 1800 integrating sphere apparatus coupled to an Ocean Optics Model ST1000 fibre spectrometer in which the same leaves are illuminated alternatively with and without fluorescence-exciting radiation. A study of the diurnal change in leaf reflectance spectra, combined with fluorescence measurements with the PAM-2000 Fluorometer show that the difference spectra are consistent with observed diurnal changes in steady-state fluorescence. Small canopies of Acer saccharum M. have been used for laboratory measurements with the CASI hyperspectral sensor...

Remote sensing of hetergeneity in photosynthetic efficiency, electron transport and dissipation of excess light in Populus deltoides stands under ambient and elevated CO2 concentrations,and in a tropical forest canopy, using a new laser-induced fluorescence transient device

Ananyev, Gennady; Kolber, Zbigniew; Klimov, Dennis; Falkowski, Paul; Berry, Joseph; Rascher, Uwe; Martin, Robin; Osmond, C Barry
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.6%
Determining the spatial and temporal diversity of photosynthetic processes in forest canopies presents a challenge to the evaluation of biological feedbacks needed for improvement of carbon and climate models. Limited access with portable instrumentation, especially in the outer canopy, makes remote sensing of these processes a priority in experimental ecosystem and climate change research. Here, we describe the application of a new, active, chlorophyll fluorescence measurement system for remote sensing of light use efficiency, based on analysis of laser-induced fluorescence transients (LIFT). We used mature stands of Populus grown at ambient (380 ppm) and elevated CO2 (1220 ppm) in the enclosed agriforests of the Biosphere 2 Laboratory (B2L) to compare parameters of photosynthetic efficiency, photosynthetic electron transport, and dissipation of excess light measured by LIFT and by standard on-the-leaf saturating flash methods using a commercially available pulse-modulated chlorophyll fluorescence instrument (Mini-PAM). We also used LIFT to observe the diel courses of these parameters in leaves of two tropical forest dominants, Inga and Pterocarpus, growing in the enclosed model tropical forest of B2L. Midcanopy leaves of both trees showed the expected relationships among chlorophyll fluorescence-derived photosynthetic parameters in response to sun exposure...

A simple alternative approach to assessing the fate of absorbed light energy using chlorophyll fluorescence

Hendrickson, Luke; Furbank, Robert Thomas; Chow, Wah S (Fred)
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.42%
We propose a simplified alternative method for quantifying the partitioning of excitation energy between photochemistry, fluorescence and thermal dissipation. This alternative technique uses existing well-defined quantum efficiencies such as PS II, leaving no 'excess' efficiency unaccounted for, effectively separates regulated and constitutive thermal dissipation processes, does not require the use of F o and F′ o measurements and gives very similar results to the method proposed by Kramer et al. [(2004) Photosynth Res 79: 209-218]. We demonstrate the use of the technique using chlorophyll fluorescence measurements in grapevine leaves and observe a high dependence on thermal dissipation processes (up to 75%) at both high light and low temperature.

A simple chlorophyll fluorescence parameter the correlates with the rate coefficient of photoinactivation of Photosystem II

Hendrickson, Luke; Forster, Britta; Pogson, Barry; Chow, Wah S (Fred)
Fonte: Kluwer Academic Publishers Publicador: Kluwer Academic Publishers
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.53%
A method of partitioning the energy in a mixed population of active and photoinactivated Photosystem II (PS II) complexes based on chlorophyll fluorescence measurements is presented. There are four energy fluxes, each with its quantum efficiency: a flux associated with photochemical electron flow in active PS II reaction centres (J PS II ), thermal dissipation in photoinactivated, non-functional PS IIs (J NF ), light-regulated thermal dissipation in active PS IIs (J NPQ ) and a combined flux of fluorescence and constitutive, light-independent thermal dissipation (J f,D ). The four quantum efficiencies add up to 1.0, without the need to introduce an 'excess' term E, which in other studies has been claimed to be linearly correlated with the rate coefficient of photoinactivation of PS II (k pi ). We examined the correlation of k pi with various fluxes, and found that the combined flux (J NPQ + J f,D = J pi ) is as well correlated with k pi as is E. This combined flux arises from Fs/F′m, the ratio of steady-state to maximum fluorescence during illumination, which represents the quantum efficiency of combined non-photochemical dissipation pathways in active PS IIs. Since Fs/F′m or its equivalent, J pi , is a likely source of events leading to photoinactivation of PS II...

Photoinhibitory printing on leaves, visualized by chlorophyll fluorescence imaging and confocal microscopy, is due to diminished fluorescence from grana

Osmond, C Barry; Schwartz, Owen; Gunning, Brian
Fonte: CSLI Publications Publicador: CSLI Publications
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.7%
By analogy with the starch printing technique, it was hypothesised that photoinhibition could be used to print images on leaves that would be invisible to the eye, but easily revealed by chlorophyll fluorescence imaging. We first illustrate the process of chlorophyll fluorescence printing on leaves of the shade plant, Cissus rhombifolia, using photographs of artefacts from starch printing experiments in the laboratory of Molisch. We then use portraits of current leaders in chlorophyll fluorescence research to demonstrate the stability of these images in living tissues. Text printing from microfilm of Ewart's pioneering studies in photoinhibition shows the resolution of the method with the fixed-focus, portable, imaging system used here. The stability of images, as well as quenching analysis of images and of leaves, suggests that localised photoinactivation, rather than sustained photoprotection, is responsible for the detail displayed by fluorescence printing. Electron micrograph positives of stained thylakoids can be printed to create an illusion of what is imagined to be the source of chlorophyll fluorescence at the membrane level. Individual chloroplasts in adjacent cells under the grid pattern of granal stacks printed on leaves were also examined using a confocal microscope. Compared with chloroplasts in the shaded parts of the grid...