Chlorophyll Fluorescence

Viruses associated to eight Alstroemeria varieties and the relationship of thrips density and environmental factors with Tomato Spotted Wilt (TSW) intensity as well as the TSW effect on yield were studied in 'Rosario' in Central Mèxico. Using hosts range the viruses detected were Tomato Spotted Wilt Tospovirus (TSWV), Impatiens Necrotic Spot Tospovirus (INSV), Alstroemeria Mosaic Potyvirus (AlMV), Alstroemeria Streak Potyvirus (ASV), Arabis Mosaic Nepovirus (ArMV), and Cucumber Mosaic Cucumovirus (CMV). With serology it was confirmed the presence of TSWV in 'Jubilee', 'Rosario', and 'Regina' varieties; INSV in 'Anabel', 'Jubilee', and 'Red Sunset'; and AlMV in 'Rosario', 'Red Sunset', 'Rosita', 'Yellow King', 'Jubilee'. and 'Rojo Sangria'. TSWV and AlMV were found coinfecting 'Rosario' plants. Five percent of plants were serologically positive to TSWV in the first flower harvest (25 Jan.-5 Apr.), 10% in the second (12 Ap.-21 June), and third (5 July-13 Sept.), and 18% in the last harvest (23 Sept.-6 Dec.). The high-est peak density of thrips (520 to 630 individuals per sticky trap) were registered when the maximum temperature was higher than 35 °C and the relative humidity was between 40% to 60%. However, such peak density was not correlated with a significant increase of TSW incidence. Number and quality of inflorescences and the stem growth rate were significantly higher (P = 0.05) in plots with asymptomatic plants than that with plants showing putative symptoms of TSW.

extraction of agron omic parameters in orch ard plots from h igh -resolu tion imagery. In : Erena M. (coord.), López-Francos A. (coord.), Montesinos S. (coord.), Berthoumieu J.-P. (coord.). The use of remote sensing and geographic information systems for irrigation management in Southwest Europe. Zaragoza : CIHEAM / IMIDA / SUDOE Interreg IVB (EU-ERDF), 2012. p. 161-174 (Options Méditerranéennes : Série B. Etudes et Recherches; n. 67

Using simultaneous measurements of leaf gas exchange and chlorophyll fluorescence, we determined the excitation partitioning to photosystem I1 (PSII), the CO,/O, specificity of ribulose-l,5bisphosphate carboxylase/oxygenase, the dark respiration in the light, and the alternative electron transport rate to acceptors other than bisphosphoglycerate, and the transport resistance for CO, in the mesophyll cells for individual leaves of herbaceous and tree species. The specificity of ribulose-1,5-bisphosphate carboxylase/ oxygenase for CO, was determined from the slope of the O , dependente of the CO, compensation point between 1.5 and 21 ?& O,. Its value, on the basis of dissolved CO, and O , concentrations at 25.5"C, varied between 86 and 89. Dark respiration i n the light, estimated from the difference between the CO, compensation point and the CO, photocompensation point, was about 20 to 50% of the respiration rate in the dark. The excitation distribution to PSll was estimated from the extrapolation of the dependence of the PSll quantum yield on F/F, to F = O, where F is steady-state and F,,, is pulse-saturated fluorescence, and varied between 0.45 and 0.6. The alternative electron transport rate was found as the difference between the electron transport rates calculated from fluorescence and from gas exchange, and at low CO, concentrations and 10 to 21 % O*, it was 25 to 30% of the maximum electron transport. l h e calculated mesophyll diffusion resistance accounted for about 20 to 30% of the total mesophyll resistance, which also includes carboxylation resistance. Whole-leaf photosynthesis is limited by gas phase, mesophyll diffusion, and carboxylation resistances in nearly the same proportion in both herbaceous species and trees.

The aim of this study was to investigate the influence of copper and vanadium ions on photosynthetic activity of carrot (Daucus carota L. subsp. sativus (Hoffm.) Schübl. & G. Martens) and winter wheat (Triticum aestivum L.). Measurements of the total chlorophyll content were performed – the SPAD chlorometer and the basic chlorophyll a fluorescence parameters were determined using the FMS-1 fluorometer – Hansatech. The studies used aqueous solutions of copper salt (CuSO4) and vanadium (H4NO3V), with molar concentrations: 0.6 mM, and 3 mM. The control group consisted of plants watered with distilled water. Both in carrots and in wheat, together with an increase in the concentration of heavy metal ions, a decrease in the content of chlorophyll was observed and significant changes in the activity of the photosystem were demonstrated II. Measurements of chlorophyll fluorescence kinetics and only in D. carota subsp. sativus showed a statistically significant effect of 3 mM solutions of co...

Regional Agrochemical Station in Lublin, Sławinkows ka 5, 20-810 Lublin, Poland Department of Agricultural and Environmental Chemis try, University of Life Sciences Akademicka 15, 20-033 Lublin, Poland Department of Plant Physiology, Institute of Biolog y and Biochemistry Maria Curie-Skłodowska University, Akademicka 19, 2 0-033 Lublin, Poland Institute of Agrophysics PAS, Do świadczalna 4, 20-290 Lublin, Poland e-mail: ptkaczyk@schr.gov.pl

Drought is a significant constraint in bean production. In this study, we used high-throughput phenotyping methods (chlorophyll fluorescence imaging, multispectral imaging, 3D multispectral scanning) to monitor the development of drought-induced morphological and physiological symptoms at an early stage of development of the common bean. This study aimed to select the plant phenotypic traits which were most sensitive to drought. Plants were grown in an irrigated control (C) and under three drought treatments: D70, D50, and D30 (irrigated with 70, 50, and 30 mL distilled water, respectively). Measurements were performed on five consecutive days, starting on the first day after the onset of treatments (1 DAT–5 DAT), with an additional measurement taken on the eighth day (8 DAT) after the onset of treatments. Earliest detected changes were found at 3 DAT when compared to the control. D30 caused a decrease in leaf area index (of 40%), total leaf area (28%), reflectance in specific green...

Background and Aims Depending on cultivar, surfaces of young leaves of Vitis vinifera may be glabrous-green ('Soultanina') or transiently have anthocyanins ('Siriki') or pubescence ('Athiri'). A test is made of the hypothesis that anthocyanins and pubescence act as light screens affording a photoprotective advantage to the corresponding leaves, and an assessment is made of the magnitude of their effect. Methods Measurements were made on young leaves of the three cultivars in spring under field conditions. Photosynthetic gas-exchange and in vivo chlorophyll fluorescence were measured. Photosynthetic and photoprotective pigments were analysed by HPLC. Key Results Compared with glabrous-green leaves, both anthocyanic and pubescent leaves had greater darkadapted PSII photochemical efficiency and net photosynthesis. In leaves possessing either anthocyanins or pubescence, the ratio of xanthophyll cycle components to total chlorophyll, and mid-day de-epoxidation state of the xanthophyll cycle were considerably smaller, than in glabrous-green leaves. These differences were more evident in pubescent leaves, probably indicating that trichomes were more effective in decreasing light stress than anthocyanins in the epidermis. Conclusions Light screens, especially in the form of pubescence, decrease the risk of photoinhibition whilst allowing leaves to maintain a smaller content of xanthophyll cycle components and depend less on xanthophyll cycle energy dissipation. This combination of photoprotective features, i.e. decreased photon flux to the photosynthetic apparatus and lower xanthophyll cycle utilization rates may be particularly advantageous under stressful conditions.

Background Most nanoparticles (NPs) have a significant impact on the structure and function of the plant photosynthetic apparatus. However, their spectrum of action varies significantly, from beneficial stimulation to toxicity, depending on the type of NPs, the concentration used and plant genotypic diversity. Photosynthetic performance can be assessed through chlorophyll a fluorescence (ChlF) measurements. These data allow to indirectly obtain detailed information about primary light reactions, thylakoid electron transport reactions, dark enzymatic stroma reactions, slow regulatory processes, processes at the pigment level. It makes possible, together with leaf reflectance performance, to evaluate photosynthesis sensitivity to stress stimuli. Results We investigated effects of different metal and metal(oid) oxide nanoparticles on photosynthesis of oakleaf lettuce seedlings by monitoring the chlorophyll a fluorescence light radiation and reflectance from the leaves. Observations of ...

This study was carried out to determine the effect of different zinc concentrations on the ecophysiological response of Salix clones: four commercial clones ("1962", "1968", "Drago", and "Levante") selected for short rotation coppice, and one natural clone, "Sacco", obtained from a contaminated area. Gas exchanges, chlorophyll a fluorescence (JIP-test), relative chlorophyll content, and biometric parameters were measured in plants grown for fifteen days in soil containing Zn concentrations of 0, 300, 750, and 1,500 mg(ZnCl 2 ) kg 1 . Ecophysiological response to metal stress differed in dependence on the Zn concentration and clone. At the low Zn concentration (300 mg kg 1 ), the absence of any significant reductions in parameters investigated indicated an efficient plant homeostasis to maintain the metal content within phytotoxic limits. Stomatal limitation, observed at 750 and 1,500 mg kg 1 , which was found in all clones after three days of the treatment, might be caused by indirect effects of metal on guard cells. Among commercial clones, "Drago" was more sensitive to Zn stress, showing inhibition of growth, while "1962" clone showed a downregulation of PSII photochemistry following the slowdown in the Calvin-Benson cycle. On the contrary, the natural Salix clone ("Sacco") performed better compared to the other clones due to activation of a photosynthetic compensatory mechanism.

Growth, net photosynthetic rate (P N ), chlorophyll fluorescence induction kinetics, and stromal fructose-1,6-bisphosphatase (sFBPase) in annual legumes native to the Mediterranean region, two clovers (Trifolium subterraneum L. ssp. oxaloides Nyman cv. Clare and T. michelianum Savi cv. Giorgia) and two Medicago species (M. polymorpha L. cv. Anglona and M. truncatula Gaertn. cv. Paraggio), shifted from 20 to 10 ºC for 1 d or developed at 10 ºC were compared with controls kept at 20 ºC. Cold development produced a larger stimulation of growth in the clover cv. Giorgia and the Medicago cv. Paraggio. Transferring plants to low temperatures affected P N relatively less in clovers than in Medicago plants. Development at 10 ºC relieved the inhibition of photosynthesis in Giorgia and Paraggio, but not in Clare and Anglona, which correlated with increases in the maximum rate of carboxylation by ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO (V cmax ), and the photon-saturated rate of electron transport (J max ). In Medicago, transfer from high to low temperature inhibited photosynthesis in a lesser extent in Anglona than in Paraggio, which showed severe limitations at level of V cmax and J max . Development at 10 ºC in Paraggio produced an efficient photosynthetic cold acclimation, this being associated with a two-fold increase of quantum yield of photosystem 2 electron transport (∆F/F' m ) and with the activity of sFBPase. By contrast, Anglona showed an irreversible inhibition of P N coupled with the reduction of carbon metabolism by impairment of Calvin cycle enzyme activities such as RuBPCO and sFBPase, resulting in a poor cold acclimation of photosynthesis in this cultivar.

Net photosynthetic rate (PN), productivity and the first phases of the fluorescence induction curve were investigated in leaves of two potato cultivars exposed to water stress. Water stress applied to potato plants at the beginning of their development (planting -bud formation) increased productivity but decreased PN and variable fluorescence (Fv) of leaves. The short-term influence of water stress on the same plants also diminished the F v.

The photosynthetic efficiency in plants is affected by salinity. Focus of this study was to observe the consequences of salinity on the rate of photosynthesis in Moringa (Moringa oleifera L.) plants. Experiment was conducted under field conditions with 3 replicates and data of treated and non-treated plants was collected accordingly. Photosynthetic rate was affected by different levels of salt stress. The change in photosynthetic was attributes were determined by OJIP and light response curve calculations by using Fluor Pen [FP 100-PS (Photon system, Czech Republic)] and DUAL-PAM-100 (Walz, Germany). Salinity stress decreased chlorophyll a fluorescence characteristic. The significant quantity of electron transport (φEo), quantum yield of primary photochemistry (φPo), proficiency per trapped excitation (Ψo) and performance index of photosystem II (PSII). Performance index (PIABS) was also declined with salinity in M. oleifera. Our results showed that electron transport rate and photo...

Gross primary production (GPP) is closely associated with processes such as photosynthesis and transpiration within ecosystems, which is a vital component of the global carbon-water-energy cycle. Accurate prediction of GPP in terrestrial ecosystems is essential for evaluating terrestrial carbon cycle processes. Machine learning (ML) models provide significant technical support in this domain. Presently, there is a deficiency of high-precision and robust GPP prediction variables and models. Challenges such as unclear contributions of predictive variables, extended model training durations, and limited robustness must be addressed. Solar-induced chlorophyll fluorescence (SIF), optimized multilayer perceptron neural networks, and ensemble learning models show the potential to overcome these challenges. This study aimed to develop an optimized multilayer perceptron neural network model and an ensemble learning model, while objectively assessing the capacity of SIF to predict GPP. Identifying robust models capable of enhancing the accuracy of GPP predictions was the ultimate goal. This study utilized continuous observations of SIF and meteorological data collected from 2020 to 2021 at a designated research observation station within the Populus plantation ecosystem of the Huanghuaihai agricultural protective forest system in Henan Province, China. By optimizing and evaluating the predictive accuracy and robustness of the models across different temporal scales (half-hourly and daily scales), a multi-layer perceptron (MLP) neural network optimization model based on the back propagation (BP) neural network (BPNN) algorithm (BP/MLP) and MLP and random forest (RF) integration (MLP-RF) ensemble models were constructed, utilizing SIF as the primary predictive variable for GPP. Both the BP/MLP (half-hourly scale model R 2 = 0.885, daily scale model R 2 = 0.921) and the MLP-RF (half-hourly scale model R 2 = 0.845, daily scale model R 2 = 0.914) models showed superior accuracy compared to the BPNN (half-hourly scale model R 2 = 0.841, daily scale model R 2 = 0.918) and the traditional RF (half-hourly scale model R 2 = 0.798, daily scale model R 2 = 0.867) models, with the BP/MLP model consistently outperforming the MLP-RF model. The BP/MLP model, which was optimized through particle swarm optimization (PSO), significantly enhanced the robustness of GPP predictions on a half-hourly scale and daily scale. Considering both half-hourly scale and daily scale in the PSO-BP/MLP modeling, the four indicators, light-use efficiency (LUE), photosynthetically active radiation (PAR), absorbed photosynthetically active radiation (APAR), and the variation in SIF with NIR v P (f SIF (NIR v P)), exhibited the potential for enhancing the accuracy of GPP predictions. This study employed a series of model optimization techniques to develop a GPP prediction model with enhanced performance that objectively evaluated the contributions of the predictive variables. This approach provided an innovative and effective method for assessing the carbon cycle in terrestrial ecosystems.

Biostimulants are substances able to improve water and nutrient use efficiency and counteract stress factors by enhancing primary and secondary metabolism. Premise of the work was to exploit raw extracts from leaves (LE) or flowers (FE) of Borago officinalis L., to enhance yield and quality of Lactuca sativa 'Longifolia,' and to set up a protocol to assess their effects. To this aim, an integrated study on agronomic, physiological and biochemical aspects, including also a phenomic approach, has been adopted. Extracts were diluted to 1 or 10 mL L(-1), sprayed onto lettuce plants at the middle of the growing cycle and 1 day before harvest. Control plants were treated with water. Non-destructive analyses were conducted to assess the effect of extracts on biomass with an innovative imaging technique, and on leaf photosynthetic efficiency (chlorophyll a fluorescence and leaf gas exchanges). At harvest, the levels of ethylene, photosynthetic pigments, nitrate, and primary (sucrose...

To assess the reliability and sensitivity of non-invasive optical methods to detect the early effects of water deficit in the field, we analyzed the time-series of non-invasive measurements obtained in a dry season in a representative collection of wheat genotypes grown in small-plot field trials, in non-irrigated and irrigated variants. Despite a progressive water deficit and significant yield loss, the measurements indicated very minor changes in chlorophyll content or canopy cover. This corresponded well to the insignificant differences in spectral reflectance normalized difference vegetation index (NDVI) values. On the other hand, we identified the significant and rapid response of fast fluorescence kinetics data following the onset of irrigation. Analysis of parameters showed the main effects of drought were associated with changes in the amplitude of the I–P phase of the OJIP transient, indicating changes at the level of photosystem I and beyond. Statistical analyses identifie...

Kopenske rastline se soočajo s problemom, kako sprejeti iz ozračja ustrezno količino CO 2 in pri tem omejiti oddajanje vode. Rešitev tega problema je uravnavanje prevodnosti listnih rež. Da je v danih razmerah dosežena optimalna prevodnost rež, se celice zapiralke odzivajo na mnoge signale iz okolja in na signale iz rastline. V članku predstavljamo odzive listnih rež na glavne abiotske dejavnike in pri prikazu učinkov teh dejavnikov uporabimo lastne rezultate porometričnih meritev. Opisan je prenos signalov v regulaciji listnih rež, v opisu so vključene nekatere nedavne ugotovitve na tem področju.

Peanut is a major oilseeds crop of India with its largest area in the world, but its productivity is less than the world average. Though India has released a number of peanut cultivars, studies on the physiological efficiencies of such varieties are scarce. In this study, we tried to elucidate the physiological basis, net photosynthesis (PN), transpiration (E), stomatal conductance (gs), chlorophyll fluorescence (Fv/Fm), SPAD chlorophyll meter reading (SCMR), chlorophyll (chl) contents in leaf at 60-65 days of crop and pod and haulm yields at harvest in 186 peanut cultivars during Kharif season. The average and range of PN were 19.8 and 11.4-31.4 μ mol m s, gs 0.25 and 0.11-0.45 m s , E 6.84 and 3.96-11.61 m mol ms, SCMR 34.0 and 20.3-44.1, total chl 7.79 and 3.07-15 mg g leaves, Fv/Fm 0.846 and 0.802-0.887, pod yield 179 and 68-309 g m and haulm yield 464 and 144-884 g m and a number of superior cultivars identified. The pod yield was strongly correlated with SCMR, chl and caroteno...

The effects of short-time fumigation (0-60 min) of intact spinach leaves with S0 2 (2 ppm) on the photosynthetic apparatus were investigated. A rather high S0 2 concentration was applied to monitor immediate effects on the fluorescence behaviour with the influence of repair processes or secondary types of damage being minimized. Three different types of in vivo chlorophyll fluorescence measurements were used: Rapid induction kinetics (Kautsky effect), slow induction kinetics with repetitive application of saturation pulses (saturation pulse method), and decay kinetics following a single turnover saturating flash. The slow induction kinetics with repetitive application of saturation pulses reacts in the most sensitive way indicating a primary damage at the level of the enzymatic reactions of the Calvin cycle. It is suggested that stromal acidification upon S0 2 uptake interferes with light activation of Calvin cycle enzymes. With longer fumigation times also damage at the level of photosystem II becomes apparent: A decrease in variable fluorescence yield reflects a lowering of photosystem II quantum yield, and the slowing down of fluorescence relaxation kinetics reveals an effect on the secondary electron transport from Q A to Q B . The detrimental effects of S0 2 depend to a great extent on the application of light during fumigation. Besides a light requirement for S0 2 uptake by stomata opening also the possibility of photoinhibitory damage is discussed. The susceptibility of leaves to photoinhibition may increase with a lowering of Calvin cycle activity by S0 2 .

Waterlogging is an important environmental stress limiting the productivity of crops worldwide. Cowpea ( Vigna unguiculata L) is particularly sensitive to waterlogging stress during the reproductive stage, with a consequent decline in pod formation and yield. However, little is known about the critical processes underlying cowpea’s responses to waterlogging during the reproductive stage. Thus, we investigated the key parameters influencing carbon fixation, including stomatal conductance (g ), intercellular CO concentration, chlorophyll content, and chlorophyll fluorescence, of two cowpea genotypes with contrasting waterlogging tolerance. These closely related genotypes have starkly contrasting responses to waterlogging during and after 7-days of waterlogging stress (DOW). In the intolerant genotype (‘EpicSelect.4’), waterlogging resulted in a gradual loss of pigment and decreased photosynthetic capacity as a consequent decline in shoot biomass. On the other hand, the waterlogging-to...

Cocoa (Theobroma cacao L.) is an important cash crop in many tropical countries, particularly in West Africa. Heat and drought are both known to affect the physiology of cocoa plants through reduced rates of photosynthesis and transpiration, as well as changed physiological processes such as the functions of photosystems, chlorophyll synthesis, stomatal conductance and expression of heat-shock proteins. This in turn leads to decreased yields and increased risks of mortality under severe heat and drought. To help cocoa plants adapt to climate change, the literature suggests agroforestry as a potential farm management practice. It has been argued that the lack of tree cover in cocoa cultivation systems exposes

Optical sensors for fluorescence of chlorophyll a (f-Chl a ) and phycocyanin (f-PC) are increasingly used as a proxy for biomass of algae and cyanobacteria, respectively. They provide measurements at highfrequency and modest cost. These sensors require site-specific calibration due to a range of interferences. Light intensity affects the fluorescence yield of cyanobacteria and algae through light harvesting regulation mechanisms, but is often neglected as a potential source of error for in-situ f-Chl a and f-PC measurements. We hypothesised that diel light variations would induce significant f-Chl a and f-PC suppression when compared to dark periods. We tested this hypothesis in a controlled experiment using three commercial fluorescence probes which continuously measured f-Chl a and f-PC from a culture of the cyanobacterium Dolichospermum variabilis as well as f-Chl a from a culture of the green alga Ankistrodesmus gracilis in a simulated natural light regime. Under light, all devices showed a significant ( p < 0.01) suppression of f-Chl a and f-PC compared to measurements in the dark. f-Chl a decreased by up to 79% and f-PC by up to 59% at maximum irradiance compared to dark-adapted periods. Suppression levels were higher during the second phase of the diel cycle (declining light), indicating that quenching is dependent on previous light exposure. Diel variations in light intensity must be considered as a significant source of bias for fluorescence probes used for algal monitoring. This is of high relevance as most monitoring activities take place during daytime and hence f-Chl a and f-PC are likely to be systematically underestimated under bright conditions. Compensation models, design modifications to fluorometers and sampling design are discussed as suitable alternatives to overcome light-induced fluorescence quenching.

Mapping the cellular refractive index (RI) is a central task for research involving the composition of microorganisms and the development of models providing automated medical screenings with accuracy beyond 95%. These models require significantly enhancing the state-of-the-art RI mapping capabilities to provide large amounts of accurate RI data at high throughput. Here, we present a machine-learning-based technique that obtains a biological specimen's real-time RI and thickness maps from a single image acquired with a conventional color camera. This technology leverages a suitably engineered nanostructured membrane that stretches a biological analyte over its surface and absorbs transmitted light, generating complex reflection spectra from each sample point. The technique does not need pre-existing sample knowledge. It achieves 10-4 RI sensitivity and sub-nanometer thickness resolution on diffraction-limited spatial areas. We illustrate practical application by performing sub-cellular segmentation of HCT-116 colorectal cancer cells, obtaining complete three-dimensional reconstruction of the cellular regions with a characteristic length of 30 μm. These results can facilitate the development of real-time label-free technologies for biomedical studies on microscopic multicellular dynamics.

Although an extensive professional literature exists on biological soil crusts (BSCs), especially on the species composition of hetero- and autotrophs forming the micro-biological comunity, micromorphological information on BSCs is extremely scarce. In our study, we focused on microstructure of the BSCs from the James Ross Island (Antarctica). We combined the approach of digital microscopy to study surface roughness of the BSCs with taxonomy of BSC-forming autotrophs and chlorophyll fluorescence study focused on the photosynthetic functioning of BSCs when exposed to controlled UV-B stress. Microprofiling of BSCs resulted in the finding that the examined BSCs might be classified as fine-grained surface with roughness characteristics: Ra (37.9 μm) and Rz (136.9 μm). The BSCs were rich in microautotrophs, both algae and cyanobacteria, however, Microcoleus sp. was found dominating species. It formed multifilament ropes on and inside the BSCs. Under UV-B stress, Microcoleus- and Nostoc-d...

It is shown that with a new flash-lamp chlorophyll (Chl) fluorescence imaging system (FL-FIS), the photosynthetic activity of several thousand points of an intact attached leaf can be screened in a non-destructive way within a few seconds. The method allows the detection of the gradients in photosynthetic capacity over different parts of the leaf. The photosynthetic activity is sensed via imaging the Chl fluorescence at its maximum Fm and at steady state Chl fluorescence Fs of the induction kinetics and by the subsequent determination of the image of the fluorescence decrease ratio (R Fd ) which is known as the vitality index of the photosynthetic apparatus. Under water stress the photosynthetic activity decreases as seen in the images of the two fluorescence ratios R Fd and Fm/Fs. Histogram and profile analysis of Chl fluorescence images and Chl fluorescence ratios allow the quantification of the differences between normal and stressed leaves with a high statistical significance.

Reflection spectra demonstrating the optical properties of leaves provide information on reflectance of some specific wavelength. These spectra allow to define the color of the leaves by chromatic coordinates and in addition also the wavelength of the &quot;dominant&quot; color of the leaves. The shape of the reflection spectra of leaves as well as the values of certain ratios exhibit typical changes between analyses leaves demonstrated structural and functional modifications as a result of adaptation to different light environment. The measurements were carried out with three types of leaves (sun, half-shade and shade) of two different pear varieties: Santa Maria and Abbas.

In Elbasan area plants are repeatedly exposed to a variety of environmental stressors which affect growth, physiological functions and yield. Industrial pollution and other stresses affect the reduction the activity of leaf photosynthetic apparatus. Among the pollutants that are generated from the processing of scrap in Elbasan are sulfur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), fine particles (PM) as well as dioxins and furans The impact of air pollution from metallurgical plants is analyzed in endemic plant Cercius Silicuastrum different distances from the source of pollution. The chlorophyll (Chl) fluorescence signatures of leaves have been widely applied as non-invasive techniques for the in vivo analysis of plant stress. The Chl fluorescence provides ample information on the photosynthetic apparatus as first discovered by Kautsky. Various ratios of the Chl fluorescence determined from the induction kinetics can be used as indicators of the stress effect to the...

Air pollution by the metallurgical units, as the other stressors, can modify the optical and fluorescence properties of leaf plants either directly or indirectly. Therefore stress effects on plants are detectable via changed on fluorescence signature of leaves. Air pollution could induce decrease of chlorophyll (Chl) content as well as significant decline of photosynthetic activity. The chlorophyll florescence as a nondestructive method for the in vivo analysis of plants allow to study the photosynthetic light processes and quantum conversion to detect stress effect on the activity of the photosynthetic apparatus. Metallurgical factory in Elbasan that release chemicals and particulates into the atmosphere is considered a source of air pollution. Some plant species grown in area near the factory were studied to evaluate the efficiency of photosynthetic apparatus in pollution conditions via chlorophyll fluorescence imaging during induction kinetics. Different fluorescence ratios which...

The chlorophyll (Chl) fluorescence signatures of leaves have been widely applied as non-invasive techniques for the in vivo analysis of plant stress. The Chl fluorescence provides ample information on the photosynthetic apparatus as first discovered by Kautsky. Various ratios of the Chl fluorescence determined from the induction kinetics can be used as indicators of the stress effect to the photosynthetic apparatus. The high resolution multi-colour Chl fluorescence imaging techniques for whole leaves have been developed over the last years. These techniques offer the new possibility to study the distribution and patchiness of fluorescence signatures over the whole leaf area. The chlorophyll fluorescence induction kinetics (Kautsky effect) of predarkened leaves (30 min) was measured using the FluorCam 700MF imaging system (Photon Systems Instrument). The images of the measured Chl fluorescence intensity were obtained on false colour, whereby blue is the lowest (zero) and red the highest fluorescence. The images of various Chl fluorescence ratios were obtained by pixel to pixel arithmetic operations performed by FluorCam software. Efficiency of photosynthetic apparatus of analyzed endemic plants grown in different environmental stress conditions was evaluated via chlorophyll fluorescence imaging during induction kinetics and the fluorescence ratios which describe the photosynthetic light processes and quantum conversion of light.

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO 2 fluxes. It was combined with extensive ground-based quantification of leaf-and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO 2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence.

SUMMARYA key target for the improvement of Oryza sativa (rice) is the development of heat‐tolerant varieties. This necessitates the development of high‐throughput methodologies for the screening of heat tolerance. Progress has been made to this end via visual scoring and chlorophyll fluorescence; however, these approaches demand large infrastructural investments to expose large populations of adult plants to heat stress. To address this bottleneck, we investigated the response of the maximum quantum efficiency of photosystem II (PSII) to rapidly increasing temperatures in excised leaf segments of juvenile rice plants. Segmented models explained the majority of the observed variation in response. Coefficients from these models, i.e. critical temperature (Tcrit) and the initial response (m1), were evaluated for their usability for forecasting adult heat tolerance, measured as the vegetative heat tolerance of adult rice plants through visual (stay‐green) and chlorophyll fluorescence (ɸ...

Groundnut is frequently constrained by environmental conditions such as drought. Within this context, it is crucial to understand physiological mechanisms and identify specific physiological traits conferring drought tolerance. The objective of this study was to investigate photosynthetic responses and physiological changes of two groundnut cultivars (drought tolerant cv. K-134 and drought sensitive cv. JL-24) subjected to different regimes of water stress conditions for a duration of 12 days. A gradual reduction in leaf water potential (ΨL), leaf area, leaf dry mass accumulation (LDW), total chlorophyll (Chl) content, net photosynthetic rate (PN), stomatal conductance(gs) and transpiration rate (E) was observed. The magnitude of reduction was comparatively greater in sensitive cultivar (JL-24). In both cultivars, intercellular CO2 concentration (Ci) was unaffected by mild stress but significantly elevated by severe stress. Water use efficiency (WUE) representing the mesophyll efficiency was greater in the tolerant cultivar K-134. The root length and dichlorophenol indophenol (DCPIP) reduction by photosystem II (PSII)  were significantly decreased only at a severe stress in both cultivars. Our results indicated the involvement of stomatal and/or non-stomatal components in decline of photosynthesis and differed between cultivars. The relationship between water stress and this metabolism is presented in the light of differential physiological responses of the investigated cultivars.

The xanthophyll cycle has been implicated as a possible photoprotective mechanism in higher plants and algae by dissipating excess excitation energy via non-photochemical q.uenching. To examine whether colonial Phaeocystis antarctica Karsten displays xanthophyll cycling, nutrient-replete c u l t u r ~s were initially grown under limiting (40 pm01 quanta m -2 s ~' ) and saturating (280 pm01 quanta m-2 S -' ) irradiances for photosynthesis and their responses to irradiance transitions were examined for 1 h under 4 treatments. The ~I I v ~v o chl-specific absorption coefficient [aml+,(h), m2 (mg chl a)-'] for the light-limiled cultures was initially lower than the light-saturated cultures while chlorophyll (chl) anormallzed fluorrscence yields were similar for both treatments. Increases in irradiance induced increases in the diatoxanthin to diadinoxanthin ratio (DT:DD, w:w) up to 9-fold whereas parallel decreases in Irradiance similarly decreased the DT:DD ratio. Light-induced Increases in DT concentration were reduced in cultures exposed to dithiothreltol (DTT), an inhibitor of DD to DT conversion. Short-term changes in DD and DT concentrations were attributed solely to xanthophyll cycling; no de novo synthesis of DD or DT was evident based on a constant sum of DD and DT in the 1 h expenmental perturbations. It was found that DD and DT de novo synthesis required long-term acclimation; the mass ratio at steady state of (DD+DT)/chl a was 0.1 and 0.4 for the low and high light treatments, respectively. Pooled results from treatment and control cultures showed a linear relationship between light-induced changes in DT/chl a concentration and F/chl a (fluorescence to chl a ratio) and the slopes depended on the initial photoacclimated state of the culture. Cellular fluorescence changes appeared to be physiologically based; aaph()L) did not change in response to abrupt irradiance changes. Xanthophyll cycling may enable P antarctica to tolerate both high light environments and sudden changes in irradidnce, which occur during austral spring due to shallow mixed layers and intermittent shading by ice or clouds.

Horticulture has become a significant agricultural venture in accelerating economic growth. Its contribution to a nation's food security, nutritional well-being, and poverty reduction and employment opportunities is pivotal. Among its various facets, fruit crops hold a prominent position, comprising a significance share of horticultural production. However, the cultivation of fruit crops demands considerable capital investment and labor input. Embracing modern technologies for fruit orchard advancement and maximizing production potential is thus deemed essential. In today's age, remote sensing emerges as a modern solution, providing efficient technology for managing crops in specific locations. Remote sensing, or RS, serves as a potent instrument facilitating the gathering and refreshing of data to formulate precise management strategies. Through the acquisition of electromagnetic data and imagery, RS enables straightforward manipulation via computer systems. Remote sensing has the potential to mitigate risks and limit harm, proving especially valuable for tailored management and precise agricultural practices, such as identifying crops, estimating areas, managing soil and nutrients, gauging biomass and yields, and evaluating damage caused by both living organisms and environmental factors. RS offers multifaceted benefits, including risk reduction, damage minimization and increased land productivity, thereby contributing to employment generation, enhanced exports and improved economic conditions, while also ensuring food and nutritional security.

The aim of the present work was to compare the effect of ultralow oxygen (ULO) with dynamic controlled atmosphere (DCA) and controlled atmosphere (CA) on the post storage quality of 'Royal Gala' and 'Galaxy' apples after long-term storage. Two experiments were carried out with 'Royal Gala' and 'Galaxy' apples, in the years 2012 and 2013, respectively. A higher internal ethylene concentration was observed in fruits stored under CA; intermediate concentration in fruits under ULO; and the lowest by fruits stored under DCA-CF (DCA based on chlorophyll fluorescence). Flesh firmness was higher in fruits stored under DCA-CF and ULO differing from CA, in the year 2012, but in 2013 fruits stored under ULO showed the highest flesh firmness, differing from CA fruits. DCA-CF is efficient in quality maintenance of 'Royal Gala' and 'Galaxy' apples. Both 'Gala' mutants stored under ULO show a similar quality maintenance to those stored under DCA-CF.

Lichens often grow in microhabitats where they absorb more light than they can use for fixing carbon, and this excess energy can cause the formation of harmful reactive oxygen species (ROS). Lichen mycobionts can reduce ROS formation by synthesizing light-screening pigments such as melanins in the upper cortex, while the photobionts can dissipate excess energy radiationlessly using non-photochemical quenching (NPQ). An inherent problem with using fluorimetry techniques to compare NPQ in pale and melanised thalli is that NPQ is normally measured through a variously pigmented upper cortex. Here we used a dissection technique to remove the lower cortices and medullas of Lobaria pulmonaria and Crocodia aurata and then measure NPQ from the underside of the thallus. Results confirmed that NPQ can be satisfactorily assessed with a standard fluorimeter by taking measurement from above using intact thalli. However, photobionts from the bottom of the photobiont layer tend to have slightly low...

Stressful episodic weather is likely to affect the C balance of trees as the climate changes, potentially altering survival. However, the role of elevated CO2 concentration ([CO2]) in tolerating off-season episodic extremes is not clear. We tested for interactive effects of elevated CO2 and springtime heat stress on photosynthesis for seven genotypes of Eucalyptus camaldulensis Dehnh. var. camaldulensis, representing its widespread distribution across south-eastern Australia. We grew clonal material under glasshouse conditions of ambient (aCO2; 400 parts per million (ppm)) or elevated (eCO2; 640 ppm) [CO2], and air temperatures of 25 : 17°C (day : night), and measured the electron transport rate in PSII (ETR), stomatal conductance to water vapour (gs) and net CO2 assimilation (A). Measurements were made before, during and after a four-day temperature excursion of 35 : 27°C. ETR and A were ~17% higher for plants grown in eCO2 than in aCO2. Photosynthesis remained stable for plants in...

O experimento foi conduzido na Fazenda Capão dos Óleos, município de Coqueiral, Minas Gerais, de 2009 a 2011, objetivando verificar as modificações na anatomia foliar em cafeeiros implantados, com o uso de polímero hidrorretentor. Para tanto coletaram-se folhas para posterior avaliação da anatomia foliar, de plantas oriundas de diferentes tratamentos (diluições, doses e locais de aplicação de polímero hidrorretentor hidratado). O experimento constou do delineamento em blocos casualizados, no esquema fatorial 4x3x2 mais 1 tratamento adicional, com quatro repetições, perfazendo um total de 25 tratamentos (100 parcelas). Os tratamentos foram constituídos de quatro doses do polímero hidrorretentor, diluídas em 400 litros de água (0,5 kg, 1,0 kg, 1,5 kg e 2,0 kg) no primeiro fator; três volumes do polímero hidrorretentor previamente diluído (1,0 litro, 1,5 litro e 2,0 litros) aplicados por planta, no segundo fator; dois locais de aplicação (misturado na cova de plantio ou colocado em uma cova lateral das mudas plantadas) no terceiro fator; e um tratamento adicional, como testemunha, sem a utilização do polímero hidrorretentor. Coletaram-se folhas para avaliação das seguintes características anatômicas: espessura do floema, diâmetro dos vasos do xilema, número dos vasos do xilema, relação entre o diâmetro polar e equatorial dos estômatos, índice estomático de plantas, densidade estomática de plantas, espessura do parênquima paliçádico e espessura do parênquima esponjoso. Modificações anatômicas que favorecem as relações hídricas das plantas estão presentes em algumas dessas, após 24 meses da implantação de cafeeiros com a aplicação de polímero hidrorretentor. Termos para indexação: Coffea arabica L., microscopia óptica, estresse hídrico, hidrogel, implantação de lavouras.

Saline and alkaline stresses affect more than 10% of the World's arable land, limiting agricultural production. Salt-induced stress may affect the Photosystem II (PSII) function, altering fluorescence emission. Therefore, changes in fluorescence are used to quantify and analyze abiotic stress responses in plants. So far, no study has been focused on the response of PSII to saline, alkaline and saline-alkaline stresses in the model legume Lotus japonicus. For the saline, alkaline and salinealkaline treatments, plants of the L. japonicus ecotypes MG20 and Gifu-129 were cultivated in sand with nutrient solution added with NaCl and NaHCO3 in different proportions. Growth, gas exchange, and chlorophyll a fluorescence transient kinetic and OJIP parameters were measured, and chlorophyll a and b determined. The analysis of the kinetic of chlorophyll a fluorescence showed that NaClderived stress sources affect the photochemical events in PSII in both ecotypes, being this effect more evident under higher pH condition, whereas alkalinity per se has a mild or no effect on these events. The saline-alkaline stress induced a more severe effect on Gifu B-129, compared with Miyakojima MG20, whereas NaCl improved primary photochemistry in MG20. Our results allow us to accept the hypothesis that both ecotypes deploy differential responses under the three stressful treatments and that the saline-alkaline stress causes higher damage levels than saline and alkaline stresses alone in relation with structures and sub-processes of the PSII.

Dramatic climate change has led to an increase in the intensity and frequency of drought episodes and, together with the high light conditions of the Mediterranean area, detrimentally influences crop production. Salicylic acid (SA) has been shown to supress phototoxicity, offering photosystem II (PSII) photoprotection. In the current study, we attempted to reveal the mechanism by which SA is improving PSII efficiency in oregano seedlings under moderate drought stress (MoDS). Foliar application of SA decreased chlorophyll content under normal growth conditions, but under MoDS increased chlorophyll content, compared to H2O-sprayed oregano seedlings. SA improved the PSII efficiency of oregano seedlings under normal growth conditions at high light (HL), and under MoDS, at both low light (LL) and HL. The mechanism by which, under normal growth conditions and HL, SA sprayed oregano seedlings compared to H2O-sprayed exhibited a more efficient PSII photochemistry, was the increased (17%) fr...

Salicylic acid (SA), an essential plant hormone, has received much attention due to its role in modulating the adverse effects of biotic and abiotic stresses, acting as an antioxidant and plant growth regulator. However, its role in photosynthesis under non stress conditions is controversial. By chlorophyll fluorescence imaging analysis, we evaluated the consequences of foliar applied 1 mM SA on photosystem II (PSII) efficiency of tomato (Solanum lycopersicum L.) plants and estimated the reactive oxygen species (ROS) generation. Tomato leaves sprayed with 1 mM SA displayed lower chlorophyll content, but the absorbed light energy was preferentially converted into photochemical energy rather than dissipated as thermal energy by non-photochemical quenching (NPQ), indicating photoprotective effects provided by the foliar applied SA. This decreased NPQ, after 72 h treatment by 1 mM SA, resulted in an increased electron transport rate (ETR). The molecular mechanism by which the absorbed l...

During winter, the light-harvesting complexes of evergreen plants change function from energy-harvesting to energy-dissipating centers. The goal of our study was to monitor changes in the composition of the photosynthetic apparatus that accompany these functional changes. Seasonal changes in chlorophyll fluorescence, pigment concentration, and abundance and phosphorylation status of photosynthetic proteins in Pinus strobus L. (sun-exposed trees) and Abies balsamea (L.) P. Mill. (sun-exposed and shaded trees) were examined in the cold winter climate of Minnesota. Results indicated typical seasonal changes in chlorophyll fluorescence and pigment concentration, with sustained reduced photosystem II (PSII) efficiency during winter, accompanied by retention of zeaxanthin and antheraxanthin, and winter increases in the pool of xanthophyll cycle pigments and lutein. In sun-exposed trees, all photosynthetic proteins that were monitored decreased in relative abundance during winter, although two light-harvesting chlorophyll a/b binding proteins (Lhcb2 and Lhcb5), and the PsbS protein, were enriched in non-summer months, suggesting a role for these proteins in winter acclimation. In contrast, shaded trees maintained most of their protein throughout winter, with reductions occurring in spring. Thylakoid protein phosphorylation data suggest winter increases in the phosphorylation of a PSII core protein, PsbH, in sun-exposed trees, and increases in phosphorylation of all PSII core proteins in shaded trees.

During winter evergreens maintain a sustained form of thermal energy dissipation that results in reduced photochemical efficiency measured using the chlorophyll fluorescence parameter F v /F m . Eastern white pine (Pinus strobus L.) and white spruce [Picea glauca (Moench) Voss] have been shown to differ in their rate of recovery of F v /F m from winter stress. The goal of this study was to monitor changes in photosynthetic protein abundance and phosphorylation status during winter recovery that accompany these functional changes. An additional goal was to determine whether light-dependent changes in light harvesting complex II (LHCII) phosphorylation occur during winter conditions. We used a combination of field measurements and recovery experiments to monitor chlorophyll fluorescence and photosynthetic protein content and phosphorylation status. We found that pine recovered three times more slowly than spruce, and that the kinetics of recovery in spruce included a rapid and slow component, while in pine there was only a rapid component to recovery. Both species retained relatively high amounts of the light harvesting protein Lhcb5 (CP26) and the PsbS protein during winter, suggesting a role for these proteins in sustained thermal dissipation. Both species maintained high phosphorylation of LHCII and the D1 protein in darkness during winter. Pine and spruce differed in the kinetics of the dephosphorylation of LHCII and D1 upon warming, suggesting the rate of dephosphorylation of LHCII and D1 may be important in the rapid component of recovery from winter stress. Finally, we demonstrated that light-dependent changes in LHII phosphorylation do not continue to occur on subzero winter days and that needles are maintained in a phosphorylation pattern consistent with the high light conditions to which those needles are exposed. Our results suggest a role for retained phosphorylation of both LHCII and D1 in maintenance of the photosynthetic machinery in a winter conformation that maximizes thermal energy dissipation.

Although many Mediterranean and xeric plant species enhance their xanthophyll-mediated thermal dissipation under drought conditions, there has been limited research on photoprotective mechanism in droughted plants from other habitats. To investigate whether wetland plants utilise this mechanism under drought conditions, and whether species differ in their responses depending on their habitat affinities, we investigated the response of six willow (Salix) species to a shortterm drought. In a greenhouse, 40 individuals per species were dried down over 4 weeks. Periodically during the drought, predawn and midday chlorophyll fluorescence measurements were taken and leaf discs were collected for pigment analysis with HPLC. Predawn water potential was also monitored throughout the experiment. All six species increased xanthophyll cycle activity and their capacity to dissipate excess energy during the drought by increasing their total de-epoxidised xanthophyll concentration and the concentration of zeaxanthin in proportion to chlorophyll. In general, habitat generalists had greater photoprotective responses than wetland specialists, while the wetland specialists had higher pre-drought nonphotochemical quenching. These differences are consistent with their contrasting photosynthetic rates. The observed variation in species drought responses suggests that their photoprotective strategies vary with habitat affinity.

Chlorophyll fluorescence is one of the very useful techniques in plant physiology because of the ease with which the user can gain detailed information on the state of photosystem II (PSII) at a relatively low cost. Detection of quantitative traits loci related to chlorophyll fluorescence have a major role in understanding the genetic mechanisms of photosynthesis. In the present research, to mapping, the genome regions controlling chlorophyll fluorescence traits, barley (Hordeum vulgare L) from 106 F8 recombinant inbred lines caused by crossing two cultivars of Badia × Kavir was used and these lines were cultured in a complementary randomized design with two replications. Traits studied include ABS/CSo, TRo/CSo, DIo/CSo, ABS/CSm, DIo/CSm, psi (Eo), TRo/RC, REo/RC, ABS/RC, DIo/RC, Area, Fv/Fm, Sm. Linkage maps were prepared using 152 SSR polymorphic markers, 72 ISSR, 7 IRAP, 29 CAAT, 27 Scot, and 15 iPBS alleles. Molecular markers were assigned on 7 chromosomes of barley. The linkage...

Arid and semiarid ecosystems in the Mediterranean are under high risk of desertification. Revegetation with native well‐adapted evergreen shrubs is desirable, but techniques for successful establishment of these species are not fully developed. Transplant shock is a key hurdle to plantation success. The application of a drought‐preconditioning treatment during the last months of nursery culture is a potential technique for reducing transplant shock. This technique has been widely applied in boreal habitats and humid temperate areas. Three representative Mediterranean species (Pistacia lentiscus, Quercus coccifera, and Juniperus oxycedrus seedlings) were exposed to classic drought‐preconditioning treatment consisting of reductions in the watering regime. The effects of preconditioning on seedling quality were assessed by cell water relationships (pressure–volume curves), minimal transpiration, leaf capacitance, chlorophyll fluorescence, and gas exchange. Moreover, seedlings were expo...