Chlorophyll a Fluorescence

The influence of copper was assessed on wild and tolerant strains of the lichen photobiont Trebouxia erici and shown to have multiple toxic effects. Addition of 4 mM copper chloride into Trebouxia media reduced growth rates of the wild type to less than 1% of control levels. It also injured cell membranes, inhibited dehydrogenase activity, altered pigment composition, and reduced activity of photosystem II. Membrane damage was assessed through measuring electrical conductivity and potassium content, dehydrogenase activity by degree of conversion of 2,3,5-triphenyl tetrazolium chloride to red triphenylformazan, and functioning of PS II by chlorophyll a fluorescence. In respect to most parameters the tolerant strain was usually less affected by copper than the wild strain and, in some cases, not at all. We demonstrated by inductively coupled plasma atomic emission spectrometry and energy-dispersive X-ray microanalysis that enriched copper in the medium resulted in increased uptake by both wild and tolerant photobiont cells, but extracellular concentrations were significantly higher in the tolerant strain. This suggested that, at least in vitro, extracellular deposition was a mechanism of copper tolerance.

Free proline accumulation has been observed in response to heavy metal stress in plants including algae, however nothing is known about its role in copper sensitivity or copper tolerance in lichen photobionts. Copper uptake, potassium efflux and free proline accumulation were determined in copper-enriched liquid cultures of wild-type Trebouxia erici as well as in copper-tolerant strain. By using inductively coupled plasma atomic emission spectrometry we found that the highest intracellular copper uptake from 2 mM copper media occurred within 4 h in both strains, but significantly less was accumulated by the tolerant strain. The copper-tolerant strain exhibited significantly more intracellular proline and significantly less potassium efflux than the wild strain. By 24 h differences between strains in intracellular copper diminished, as concentrations in both strains reached their highest levels. At the same time proline accumulations decreased significantly. Growth, pigment content, chlorophyll a degradation and chlorophyll a fluorescence were decreased by high copper concentration in the agar media after 2 weeks of cultivation, more pronounced in wild-type of T. erici. Adding proline alleviated the toxic effects of copper in both strains, but markedly so in the case of the tolerant strain.

Temperature response curves of chlorophyll a Xuorescence parameters were used to assess minimum subzero temperature assuring functioning of photosynthetic photochemical processes in photosystem II (PS II) of Antarctic lichens. Umbilicaria Antarctica and Xanthoria elegans were measured within the temperature range from ¡20 to +10°C by a Xuorometric imaging system. For potential (F V /F M) and actual (II) quantum yields of photochemical processes the minimum temperature was found to be between ¡10 and ¡20°C. Non-photochemical quenching (NPQ) of absorbed excitation energy increased with temperature drop reaching maximum NPQ at ¡15°C. Image analysis revealed intrathalline heterogeneity of chlorophyll a Xuorescence parameters with temperature drop. Temperature response of II exhibited an S-curve with pronounced intrathalline diVerences in X. elegans. The same relation was linear with only limited intrathalline diVerence in U. antarctica. The results showed that Antarctic lichen species were well adapted to sub-zero temperatures and capable of performing primary photosynthesis at ¡15°C.

One prominent difference between the photosystem II (PSII) reaction center protein D1′ in Synechocystis 6803 and normal D1 is the replacement of Phe‐186 in D1 with leucine in D1′. Mutants of Synechocystis 6803 producing only D1′, or containing engineered D1 proteins with Phe‐186 substitutions, were analyzed by 77 K fluorescence emission spectra, chlorophyll a fluorescence induction yield and decay kinetics, and flash‐induced oxygen evolution. Compared to D1‐containing PSII centers, D1′ centers exhibited a 50% reduction in variable chlorophyll a fluorescence yield, while the flash‐induced O2 evolution pattern was unaffected. In the F186 mutants, both the P680+/QA − recombination and O2 oscillation pattern were noticeably perturbed.

Mutants of the cyanobacterium Synechocystis sp. PCC 6803 with N‐terminal changes in the photosystem (PSII) II D1 protein were analysed by flash‐induced oxygen evolution, chlorophyll a fluorescence decay kinetics and 77 K fluorescence emission spectra. The data presented here show that mutations of the Thr‐2, Thr‐3 and Thr‐4 in D1 do not influence the oxygen evolution. A perturbation on the acceptor side was observed and the importance of the N‐terminal threonines for an efficient energy transfer between the phycobilisome and PSII and for stability of the PSII complex was demonstrated.

The distribution of phytoplankton and the diversity of environmental conditions for their growth around the South Island, New Zealand, were examined in May 1989 by way of chlorophyll a fluorescence profiling in combination with discrete sample analysis of nutrients and particulates, CTDprofiles, and concurrent satellite images of sea surface temperature (SST). A composite of 7 overlaid SST images from the period of the cruise emphasised the strong north-south and east-west gradients in the oceanic environment. Water column sampling coupled with SST imagery was used to examine the frontal structure in Cook Strait, upwelling along the West Coast, gradients across the Solander Trough and through Foveaux Strait, and oceanographic features associated with the Subtropical Convergence off the East Coast and over Chatham Rise. A correlation analysis of the near-surface water properties showed the zonal relationships between nutrients, nutrient ratios, and temperature, but also underscored the strong local influence of freshwater inputs around the South Island coastline. An analysis of the in vivo fluorescence data revealed large site-to-site differences M90066

One of the most important diseases of eucalyptus plantations is caused by the rust fungus Puccinia psidii. While the genetic basis of rust resistance has been addressed recently, little is known about the physiological aspects of Eucalyptus-P. psidii interaction. In order to fill this gap, we undertook a study investigating the effects of P. psidii infection on photosynthetic processes of two E. urophylla clones with contrasting resistance to the pathogen. Our results show that gas exchange and chlorophyll a fluorescence parameters were virtually unaffected in the resistant clone. In the susceptible clone, photosynthetic rates were chiefly constrained by biochemical limitations to carbon fixation. Photosynthesis was impaired only in symptomatic tissues since the reductions in photosynthetic rates were proportional to the diseased leaf area. Rust infection provoked chronic photoinhibition to photosynthesis in the susceptible clone. Overall, differences in the ability for light capture, use and dissipation may play a significant role in explaining the clonal differences in Eucalyptus in response to P. psidii infection. To our knowledge, this is the first report of the effect of rust infection on gas exchange and chlorophyll a fluorescence parameters in Eucalyptus. Keywords Eucalyptus Á Light-saturated photosynthesis Á Puccinia psidii infection Á Biochemical and photochemical impairment Communicated by Z. Gombos.

After preheating of Amaranthus chloroplasts at elevated temperatures (up to 45°C), the chlorophyll a fluorescence level under low excitation light rises as compared to control (unheated) as observed earlier in other chloroplasts (Schreiber U and Armond PA (1978) Biochim Biophys Acta 502:138-151). This elevation of heat induced fluorescence yield is quenched by addition of 0.1 mM potassium ferricyanide, suggesting that with mild heat stress the primary electron acceptor of photosystem II is more easily reduced than the unheated samples. Furthermore, the level of fluorescence attained after illumination of dithionite-treated samples is independent of preheating (up to 45°C). Thus, these experiments indicate that the heat induced rise of fluorescence level at low light can not be due to changes in the elevation in the true constant F0 level, that must by definition, be independent of the concentration of QA. It is supposed that the increase in the fluorescence level by weak modulated light is either partly associated with dark reduction of QA due to exposure of chloroplasts to elevated temperature or due to temperature induced fluorescence rise in the so called inactive photosystem II centre where QA are not connected to plastoquinone pool. In the presence of dichlorophenyldimethylurea the fluorescence level triggered by weak modulated light increases at alkaline pH, both in control and heat stressed chloroplasts. This result suggests that the alkaline pH accelerates electron donation from secondary electron donor of photosystem II to QA both in control and heat stressed samples. Thus the increase in fluorescence level probed by weak modulated light due to preheating is not solely linked to increase in true F0 level, but largely associated with the shift in the redox state of QA, the primary stable electron acceptor of photosystem II. Abbreviations; ADRY-Acceleration of Deactivation of Reaction of Enzyme Y; CCCP-Carbonyi cyanide 4-(trifluoromethoxy)-phenylhydrazone; Chl-Chlorophyll; DCMU-3-(3,4-dichlorophenyl)-1,1-dimethylurea; FeCN-potassium ferricyanide; HEPES-4-(2-hydroxy ethyl)-1-piperazine ethane sulfonic acid; LHCP-Light harvesting chlorophyll protein; MES-(4-morpholine ethane sulfonic acid); PS-photosystem; QA and QB-first and second consecutive electron acceptors of photosystem II; TES-(2-[tris(hydroxymethyl)methylamino]-l-ethanesulfonic acid) sulfonic acid; TRICINE-N-[tris(hydroxymethyl)methyl] glycine

The phytotoxic effects of the lichen secondary metabolite-usnic acid on cultures of free living alga-Scenedesmus quadricauda (UTEX 76) and aposymbiotically grown lichen photobiont Trebouxia erici (UTEX 911) were assessed. We found a relatively strong inhibition effect of usnic acid on the growth of alga Scenedesmus, accompanied by an increase of cell size, an alteration of assimilation pigment composition, followed by strong degradation of chlorophyll a, a decrease of chlorophyll a fluorescence, and an increase of reactive oxygen species in the cells. The content of soluble proteins remained a stable parameter. Phytotoxicity of usnic acid on cultures of Trebouxia photobiont was significantly lower. Usnic acid in lichens may act as an allochemical that controls the division of photobiont cells, thereby regulating the balance between the photobiont and mycobiont forming thallus. Higher tolerance to usnic acid in Trebouxia cultures may be an adaptation resulting from the long term co-evolution of these algae with fungi that produce secondary metabolites.

The recovery of lichen communities on metal-rich historical ore-roasting beds west of Sudbury has been slow, and our objective was to locate and measure metals in Cladonia pleurota, the most frequently encountered roast bed lichen species. Particulates incorporated into the thallus on or near the roast bed contained high Fe, Al, Cu and Ni, and inductively coupled plasma-atomic emission spectroscopy showed lower concentrations of heavy metals in the control site 60 km upwind than in the roast bed or an immediately adjacent forest. Wavelength-dispersive X-ray spectrometry indicated potentially toxic levels of Cu, Ni, Fe and Al in both the mycobiont and photobiont in the roast bed. The physiology of roast bed lichens was consistent with damage found in metal-treated photobionts in culture: lower concentrations of chlorophyll a, chlorophyll b and total carotenoids on or near the roast bed than in the control site. In addition chlorophyll a on the roast bed was more subject to phaeophytinization and the yield of photosystem II, as measured by F v /F m , was significantly less in both of the metal-rich sites than in the control. Thin-layer densitometry and UV spectrophotometry showed no significant difference in the amount of usnic acid between metal-rich and control sites, but heavy metals were associated with crystals of usnic acid, possibly forming complexes.

The aim of study was to analyse quality indices of pork from Lithuanian market. Samples of pork loin (m. longissimus dorsi) were analysed. The country of origin for pork was Lithuania, Poland and Germany. Samples were selected in random way in supermarkets and were analysed by standard methods. Chemical and technological characteristics were determined, sensory analysis was carried out also. Short chain fatty acids (such as lauric, myristic, palmitic) dominated in pork imported to Lithuania. Polish origin pork had highest amount of volatile fatty acids. Qualitative differences between raw meat samples were not determined, as there were not significant differences between amount of protein, protein without collagen, and connective tissue in raw meat, cooking and defrosting losses. Comparison of raw meat colour characteristics showed the same lightness L* level for all samples, the highest coordinate a* for Polish origin samples, and the lowest coordinate b* for Lithuanian origin samples. Colour characteristics of cooked samples of German origin pork loin were most light. Sensory analysis determined that were no significant differences between sensory properties and acceptability of meat samples from Lithuania and Germany (p<0.05). In comparison, samples of pork loin from Poland had more intensive color and juiciness than Lithuanian origin samples. Instrumental analysis determined that pork loin from Lithuania has higher gumminess and cohesiveness.

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.

The cultivars performance under salinity was measured in open field conditions using the Fv/Fm and Performance Index. Measurements of growth parameters as well as other chlorophyll fluorescence parameters (RC/CS, TFm, RC/ABS and ABS/RC) were also included. Giza 129 is considered salt-tolerant, and Giza 123 is salt sensitive cultivar. Both cultivars, along with Giza 132 (moderately salt tolerant), were used to evaluate the relative expression of the B2 and shmt genes at 0,100 and 200 mM NaCl. The expression of both genes increased in the tested cultivars upon salinity treatment. At 200 mM NaCl, B2 and shmt genes relative expression reached 1.9-and 1.5-folds in the salt-tolerant cultivar (Giza 129); while getting 1.6 and 1.2 folds in the sensitive cultivar (Giza 123). Repeating the same experiment for Giza 129, 132, and 123 under the growth chamber conditions revealed that the effect of salinity was more vigorous at the physiological and morphological levels. In addition, the gene expression was generally higher than that of the open field conditions, although exhibiting a similar trend of results. Our results under the present study indicate that Giza 129 is a candidate for further salinity-breeding studies. Furthermore, a comparison between growth chamber and open field conditions revealed a kind of adaptation of barley PSII to the continuous salt stress in the open field conditions.

Three distinct states can be identified for cells of the green alga Chlorella vulgariy,, State 1 and State 2 obtained by preillumination in far-red and red light, respectively, and the dark state obtained by dark-adaptation. Addition of the inhibitor DCMU to algal cells leads to an initial rapid increase in chlorophyll-a fluorescence reflecting the closure of Photosystem II traps. This, in the case of dark and state-2-adapted algae is followed by a slow light-dependent increase to a fluorescence yield typical of State-l-adapted cells. Measurements of low temperature (77 K) emission spectra indicate that the low fluorescence yields of dark and State-2-adapted algae reflect similar balances in excitation-energy distribution between the two photosystems. In both cases, the balance favours PSI and the slow fluorescence increase seen in the poisoned algae reflects a redressing of this balance in favour of PS II. The low fluorescence yield of State-2-adapted algae is thought to be associated with the phosphorylation of chlorophyll a/b light-harvesting protein (Biochim. Biophys. Acta (1983) 724, 94-103). Measurements of the uncoupler and ATPase sensitivity of the light-dependent increases seen in DCMU-poisoned cells indicate that the low fluorescence yield of darkadapted algae is of different origin. Evidence is presented showing that the light-driven changes in excitation-energy distribution seen in green algae involve two distinct processes; a low-intensity, wavelenghtindependent change reflecting simple light/dark changes and a higher intensity, wavelength-dependent change reflecting State 1/State 2 adaptation. The former changes appear to be associated with changes in the local ionic environment within the algal chloroplast, whilst the latter appear to reflect changes in the phosphorylation state of chlorophyll a/b light-harvesting protein.

Shade tolerance, the minimum light requirement for plant survival, is a key trait for understanding community assembly and forest dynamics. However, it is poorly defined for tree species to date. Current methods of measuring shade tolerance vary considerably in their performance. For instance, some measures of shade tolerance are unreliable except under some specific conditions. Therefore, it is necessary to compare the performance of these methods to provide guidance of choosing appropriate shade tolerance measures in future studies. We collected a large dataset of light traits and other life history traits for 137 understory wood species in a subtropical forest and tested the performance of five commonly used shade-tolerance indices. Results showed that all the shade-tolerance measures, except the low-light abundance index, performed poorly in distinguishing and ranking shade tolerance of the tested species. The shade tolerance quantified by the low-light abundance was consistent ...

The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled&quot;Upwelling events, coastal offshore exchange, links to biogeochemical processes&quot; 20 presentations were given,including 7 talks and 13 posters related to the ...

The level and distribution of tropospheric ozone in remote and wildness areas of the Maurienne valley, a main axis in European transport, were determined during summertime 2004 and 2005. A comprehensive distribution of biological and chemical sensors based on the commonly used ozone sensitive Bel-W3 tobacco and the passive sampling system, was set up. A significant positive correlation was observed between the two methods and the continuous ozone monitors set in three instrumental co-locations. Moreover, results from this air quality network showed that, within a natural pathway of mass airflow, altitude and climate induced variations in plant responsiveness to ozone. Three different ozone diurnal patterns could thus be clearly identified. Biological sensing to determine ozone levels in regional-scale air quality assessment proved to be accurate at low altitudes. However, Tobacco response was limited in harsh mountainous conditions. This was probably due to a decrease of plant sensitivity.

This work aimed to evaluate if gas exchange and PSII photochemical activity in maize are affected by different irradiance levels during short-term exposure to elevated CO 2. For this purpose gas exchange and chlorophyll a fluorescence were measured on maize plants grown at ambient CO 2 concentration (control CO 2) and exposed for 4 h to short-term treatments at 800 µmol(CO 2) mol-1 (high CO 2) at a photosynthetic photon flux density (PPFD) of either 1,000 µmol m-2 s-1 (control light) or 1,900 µmol m-2 s-1 (high light). At control light, high-CO 2 leaves showed a significant decrease of net photosynthetic rate (P N) and a rise in the ratio of intercellular to ambient CO 2 concentration (C i /C a) and water-use efficiency (WUE) compared to control CO 2 leaves. No difference between CO 2 concentrations for PSII effective photochemistry (Φ PSII), photochemical quenching (q p) and nonphotochemical quenching (NPQ) was detected. Under high light, high-CO 2 leaves did not differ in P N , C i /C a , Φ PSII and NPQ, but showed an increase of WUE. These results suggest that at control light photosynthetic apparatus is negatively affected by high CO 2 concentration in terms of carbon gain by limitations in photosynthetic dark reaction rather than in photochemistry. At high light, the elevated CO 2 concentration did not promote an increase of photosynthesis and photochemistry but only an improvement of water balance due to increased WUE.

Effects of elevated CO 2 on photosynthetic CO 2 assimilation, PSII photochemistry and photoinhibition were investigated in the leaves of a fast growing tropical tree species, Gmelina arborea (Verbenaceae) during summer days of peak growth season under natural light. Elevated CO 2 had a significant effect on CO 2 assimilation rates and maximal efficiency of PSII photochemistry. Chlorophyll a fluorescence induction kinetics were measured to determine the influence of elevated CO 2 on PSII efficiency. During midday, elevated CO 2-grown Gmelina showed significantly higher net photosynthesis (p < 0.001) and greater F V /F M (p < 0.001) than those grown under ambient CO 2. The impact of elevated CO 2 on photosynthetic rates and Chl a fluorescence were more pronounced during midday depression where the impact of high irradiance decreased in plants grown under elevated CO 2 compared to ambient CO 2-grown plants. Our results clearly demonstrate that decreased susceptibility to photoinhibition in elevated CO 2 grown plants was associated with increased accumulation of active PSII reaction centers and efficient photochemical quenching. We conclude that elevated CO 2 treatment resulted in easy diminution of midday photosynthetic depression.

Natural Resources Research Institute (NRRI) staff sampled and characterized benthic macroinvertebrate and aquatic plant communities in the wetland complex located southwest of Munger Landing in the St. Louis River estuary in Duluth MN.  They compared this wetland complex with appropriate reference locations in the estuary. This work was
completed under the terms of a contract with the U.S. Fish and Wildlife Service (USFWS) contract # F16AC00425. Fieldwork was completed from May 16, 2016 through October 31, 2016. Funding was supported by Great Lakes Restoration Initiative Funds administered by the U.S. Department of Interior, Fish and Wildlife Service.

In the spring of 1992 an optical closure experiment was conducted at Lake Pend Oreille, Idaho. A primary objective of the experiment was to compare techniques for the measurement of the spectral absorption coefficient and other inherent optical properties of natural waters. Daily averages of absorption coefficients measured using six methods are compared at wavelengths of 456, 488, and 532 nm. Overall agreement was within 40% at 456 nm and improved with increasing wavelength to 25% at 532 nm. These absorption measurements were distributed over the final 9 days of the experiment, when bio‐optical conditions in Lake Pend Oreille (as indexed by the beam attenuation coefficient cp(660) and chlorophyll a fluorescence profiles) were representative of those observed throughout the experiment. However, profiles of stimulated chlorophyll a fluorescence and beam transmission showed that bio‐optical properties in the lake varied strongly on all time and space scales. Therefore environmental va...

The objective of this study was to verify the physiological alterations caused by Sugarcane yellow leaf virus (ScYLV), one of the most important viral diseases of sugarcane (Saccharum officinarum L.). We analyzed the levels of soluble sugars and the activity of peroxidases in different Brazilian sugarcane varieties, with different levels of resistance and susceptibility to the virus. Comparison was also carried out between the leaf blade and the main ribs of +1 and +4 leaves, from healthy and infected plants. Soluble sugars levels (especially sucrose) were found to be higher in leaves of symptomatic infected plants, but not in healthy or asymptomatic infected plants. There was a significant increase in the content of soluble sugars in the main ribs of infected plants, followed by the leaf blade of +1 leaves. The activity of peroxidases was significant higher in symptomatic infected plants compared to healthy or infected plants without symptoms.

L'utilisation des rapid light curves (RLC) et des steady state light curves (SSLC), pour la caractérisation in situ de l'activité photosynthétique du phytoplancton, à différentes échelles de temps, a été comparée. La possibilité d'utiliser les paramètres photosynthétiques des RLC pour prédire ceux de SSLC a été évaluée. Les résultats montrent que les RLC sont un bon outil pour la caractérisation de l'activité photosynthétique à différentes échelles temporelles. Mots clés: activité photosynthétique, phytoplancton, rapid light curves, steady state light curves The use of rapid light curves (RLC) and steady state light curves (SSLC), for in situ characterization of phytoplankton photosynthetic activity, at different time scales, was compared. The possibility to use RLC to predict SSLC photosynthetic parameters was evaluated. The results showed that RLC are a good tool to characterize photosynthetic activity at different temporal scales.

The study examined photosynthetic efficiency of two barley landraces (cvs. Arabi Abiad and Arabi Aswad) through a prompt fluorescence technique under influence of 14 different abiotic stress factors. The difference in the behavior of photosynthetic parameters under the same stress factor in-between cv. Arabi Abiad and cv. Arabi Aswad indicated different mechanisms of tolerance and strategies for the conversion of light energy into chemical energy for both the landraces. This study confirmed the suitability of some chlorophyll fluorescence parameters as reliable biomarkers for screening the plants at the level of photosynthetic apparatus.

Analysis of plant behavior under diverse environmental conditions would be impossible without the methods for adequate assessment of the processes occurring in plants. The photosynthetic apparatus and its reaction to stress factors provide a reliable source of information on plant condition. One of the most informative methods based on monitoring the plant biophysical characteristics consists in detection and analysis of chlorophyll a fluorescence. Fluorescence is mainly emitted by chlorophyll a from the antenna complexes of photosystem II (PSII). However, fluorescence depends not only on the processes in the pigment matrix or PSII reaction centers but also on the redox reactions at the PSII donor and acceptor sides and even in the entire electron transport chain. Presently, a large variety of fluorometers from various manufacturers are available. Although application of such fluorometers does not require specialized training, the correct interpretation of the results would need sufficient knowledge for converting the instrumental data into the information on the condition of analyzed plants. This review is intended for a wide range of specialists employing fluorescence techniques for monitoring the physiological plant condition. It describes in a comprehensible way the theoretical basis of light emission by chlorophyll molecules, the origin of variable fluorescence, as well as relations between the fluorescence parameters, the redox state of electron carriers, and the light reactions of photosynthesis. Approaches to processing and analyzing the fluorescence induction curves are considered in detail on the basis of energy flux theory in the photosynthetic apparatus developed by Prof. Reto J. Strasser and known as a "JIP-test." The physical meaning and relation of each calculated parameter to certain photosynthetic characteristics are presented, and examples of using these parameters for the assessment of plant physiological condition are outlined.

In recent decades, a new class of polymeric materials, PAMAM dendrimers, has attracted marked interest owing to their unique nanoscopic architecture and their hopeful perspectives in nanomedicine and therapeutics. However, the potential release of dendrimers into the aquatic environment raises the issue about their toxicity on aquatic organisms. Our investigation sought to estimate the toxicity of cationic PAMAM dendrimers on the green alga, Chlamydomonas reinhardtii. Algal cultures were exposed to different concentrations (0.3-10 mg L −1) of low dendrimer generations (G2, G4 and G5) for 72 h. Potential adverse effects on Chlamydomonas were assessed using esterase activity (cell viability), photosynthetic O 2 evolution, pigments content and chlorophyll a fluorescence transient. According to the median inhibitory concentration (IC 50) appraised from esterase activity, toxicity on cell viability decreased with dendrimer generation number (2, 3 and 5 mg L −1 for G2, G4 and G5 dendrimers, respectively). Moreover, the three generations of dendrimers did not induce the same changes in the photosynthetic metabolism of the green alga. O 2 evolution was stimulated in cultures exposed to the lowest generations tested (i.e. G2 and G4) whereas no significant effects were observed with G5. In addition, total chlorophyll content was increased after G2 treatment at 2.5 mg L −1. Finally, G2 and G4 had positive effects on photosystem II (PSII): the amount of active PSII reaction centers, the primary charge separation and the electron transport between Q A and Q B were all increased inducing activation of the photosynthetic electron transport chain. These changes resulted in stimulation of full photosynthetic performance.

Silicon (Si) has beneficial effects on the tolerance of plants to various biotic and abiotic stresses. The objective of this study was to determine the effect of Si nutrition in tomato grown under conditions of induced saline stress (S), on leaf temperature, chlorophyll fluorescence and stomatal conductance (gs). The experiment was conducted under greenhouse conditions during the springsummer 2017 cycle. A randomized distributed plot design was used. In which the main plot was salinity [with NaCl or with standard nutrient solution (SNS)] and the subplot was the application of Si (0, 4, 8 g L). The variables were measured during the day. The results showed that the leaf temperature increased at dawn in plants with NaCl and at sunset the effect was reversed and the highest values were in plants with SNS. At noon, Si × S interaction was identified in the photosynthetic efficiency (Fv/Fm) and minimal fluorescence (Fo) variables. The maximum fluorescence (Fm) was more affected by the typ...

Soil drought is a major problem in plant cultivation. This is particularly true for thermophilic plants, such as maize, which grow in areas often affected by precipitation shortage. The problem may be alleviated using plant growth and development stimulators. Therefore, the aim of the study was to analyze the effects of 5-aminolevulinic acid (5-ALA), zearalenone (ZEN), triacontanol (TRIA) and silicon (Si) on water management and photosynthetic activity of maize under soil drought. The experiments covered three developmental stages: three leaves, stem elongation and heading. The impact of these substances applied during drought stress depended on the plant development stage. 5-ALA affected chlorophyll levels, gas exchange and photochemical activity of PSII. Similar effects were observed for ZEN, which additionally induced stem elongation and limited dehydration. Beneficial effects of TRIA were visible at the stage of three leaves and involved leaf hydration and plant growth. A silicon preparation applied at the same developmental stage triggered similar effects and additionally induced changes in chlorophyll levels. All the stimulators significantly affected transpiration intensity at the heading stage.

The effectiveness of exogenously applied zearalenone (ZEN) in alleviating water deficiency stress of pea (Pisum sativum L.) and yellow lupine (Lupinus luteus L.) was analyzed in the pot experiment. ZEN was applied in the form of spraying in the flowering phase on the first day of induced drought. The effectiveness of ZEN was evaluated based on physiological (electrolyte leakage, greenness, and photosystem II activity) and biochemical (protein, proline, ascorbic acid contents, and antioxidant enzyme activity) parameters after 14 days of drought. The yield and yield quality defined as yield components, total protein, fats, sugars, and antioxidants (tocopherols and β-carotene) were measured in newly formed seeds. ZEN residue in the seeds was analyzed employing UHPLC-MS/MS to exclude its accumulation. The results showed the possibility of reducing the effects of drought stress through the use of ZEN. It was manifested by increased cell membranes stability and antioxidant enzyme activity...

Soil drought is a major problem in plant cultivation. This is particularly true for thermophilic plants, such as maize, which grow in areas often affected by precipitation shortage. The problem may be alleviated using plant growth and development stimulators. Therefore, the aim of the study was to analyze the effects of 5-aminolevulinic acid (5-ALA), zearalenone (ZEN), triacontanol (TRIA) and silicon (Si) on water management and photosynthetic activity of maize under soil drought. The experiments covered three developmental stages: three leaves, stem elongation and heading. The impact of these substances applied during drought stress depended on the plant development stage. 5-ALA affected chlorophyll levels, gas exchange and photochemical activity of PSII. Similar effects were observed for ZEN, which additionally induced stem elongation and limited dehydration. Beneficial effects of TRIA were visible at the stage of three leaves and involved leaf hydration and plant growth. A silico...

Within the world ocean, the western subarctic Pacific is known as the region with the largest seasonal drawdown in the partial pressure of CO2 due to biological activity, i.e., high spring primary production and particulate organic carbon flux. These distinctive features are mainly caused by intense spring diatom blooms in coastal Oyashio (COY) and Oyashio (OY) waters. Although phytoplankton assemblages in OY waters are rather well studied, little is known about COY waters. In this study, photophysiological properties and phytoplankton community composition in COY waters were investigated during the pre-bloom and bloom periods from March to April 2015. Next-generation sequencing targeting the 18S rRNA gene revealed that the diatom Thalassiosira generally dominated the phytoplankton community and showed distinct differences in the diatom communities in shelf and offshore waters of the COY. Additionally, the  PSII [nm 2 quanta-1 ]

Photon arrival time statistics significantly affect the performance of the photosynthetic system under a pulsedlight regime when the average number of photons hitting the Chlorophyll antenna of PS II is small. As a result, the interpretation of measurements of the production rate of biomass or other products of unicellular algae under a pulsed-light regime and the comparison of the results with those obtained under continuous illumination depends crucially upon accounting for these statistics.

Images of chlorophyll-a-fluorescence oscillations were recorded using a camera-based fluorescence imaging system. Oscillations with frequencies around 1 per min were initiated by a transient decrease in light intensity during assimilation at an elevated CO2-concentration. The oscillation was inhomogenously distributed over the leaf. In cells adjacent to minor veins, frequency and damping rate was high, if there was any oscillation. In contrast, the amplitude was highest in Cells most distant from phloem elements (maximal distance about 300/2m). The appearance of minor veins in oscillation images is explained by a gradient in the metabolic control in the mesophyll between minor veins and by transport of sugar from distant cells to phloem elements. The potential of fluorescence imaging to visualize 'microscopic' source-sink interactions and metabolic domains in the mesophyll is discussed.

Quatro gramíneas forrageiras (Setaria anceps Stapf., Hemarthria altissima [Poir] Stapf. & Hubbard, Acroceras macrum Stapf. e Brachiaria purpurascens [Raddi] Henr.), foram estabelecidas por mudas, em vasos plásticos com diferentes condições hídricas, para se avaliar algumas características morfogênicas e estruturais. As irrigações foram controladas pela pesagem individual dos vasos e pela saturação relativa à porosidade total (SRPT) para cada nível hídrico do solo. Utilizou-se o delineamento de blocos casualizados, com três repetições, em que os tratamentos consistiram de quatro espécies, submetidas a quatro níveis hídricos: deficiência hídrica (50% de SRTP) (D); controle (100% de SRTP) (C); alagamento 1 (120% de SRTP) (A1) e alagamento 2 (150% de SRTP) (A2). Foram identificados três perfilhos basais vaso-1, para as mensurações da morfogênese e das características estruturais das plantas: taxa de aparecimento de folhas individuais (TAP), filocrono de folhas individuais (FIL), taxa de...

Chlorophyll a fluorescence analysis reveals divergent photosystem II responses to saline, alkaline and saline-alkaline stresses in the two Lotus japonicus model ecotypes MG20 and Gifu-129.-Manuscript Draft-Manuscript Number: ACPP-D-18-00793R3 Full Title: Chlorophyll a fluorescence analysis reveals divergent photosystem II responses to saline, alkaline and saline-alkaline stresses in the two Lotus japonicus model ecotypes MG20 and Gifu-129.

In the context of seaside landscaping, one of the greatest challenges for practitioners and scientists is to select suitable species that are able to tolerate salt spray. This is the key aspect for a wide number of potentially suitable species. The objectives of this study were (1) to identify plant traits associated with species tolerance to salt stress and (2) to evaluate the responses of different shrub species to salt spray. For this purpose, a study was conducted to determine the effects of salt spray on twenty-four ornamental shrubs using rapid and easy-to-use methodology. The species were subjected twice a week to nebulization treatment with simulated seawater solution for 60 days. Every 20 days, net photosynthesis, stomatal conductance, transpiration rate, and chlorophyll a fluorescence were determined. Furthermore, dry biomass of the different organographic portions, leaf number, leaf area, Specific Leaf Area, chlorophyll content, and leaf damage were determined at the end ...

Physiological and biochemical responses to acute ozone exposure for 29 plants belonging to natural and semi-natural european ecosystems were characterised and used to reveal common features among species. Plants were grown in controlled conditions and exposed to acute ozone fumigation at 150 ppb for 3 h. Parameters of chlorophyll a fluorescence, pigments content and antioxidant enzyme activity were measured in control and ozone-treated plants and the data obtained from these analyses was used to perform multivariate statistics. The results indicated that the treatment with ozone and the species diversity, as well as the interaction between the two factors, were able to significantly affect the variables as a whole. Ozone treatment affected plant metabolism to different extents for the different species, even if the statistical analyses performed proved that most of them could be grouped in two main clusters. The first cluster is mainly affected in the photosynthetic performance, as indicated by the decrease in the F v /F m ratio and the increase in the de-epoxidation index, while the second one grouped species characterised by strong reductions in leaf pigment content and by increases in peroxidase activity. The observation that most of the parameters analysed were differently affected by the treatment in the natural and semi-natural species investigated pointed out that the different constitutive metabolic behaviour could account for a different susceptibility to the pollutant and, as a consequence, for a different performance of some of the species in heavily polluted environments.

IntroductionThe up-side down jellyfish Cassiopea andromeda represents a yet untapped marine species that could be targeted as a new source for functional ingredients, such as natural pigments and antioxidants. Since C. andromeda hosts endosymbiotic dinoflagellates, this jellyfish contains peridinin pigments, which are linked with high antioxidant capacities and many other health-promoting properties. This study investigates the potential to specifically increase the content of peridinin and overall antioxidant activity in C. andromeda, through the targeted application of different photosynthetic active radiation (PAR) intensities and ultraviolet radiation, cultured in fully controlled indoor aquaculture systems.Materials and MethodsIndoor bred C. andromeda specimens were exposed to five different PAR intensities (50, 100, 200, 400 and 800 µmol photons m−2 s−1) and a combined treatment of narrow-band UVB (λ = 285 ± 10 nm) radiation and intermediate (200 µmol photons m−2 s−1) PAR inte...