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Thalli of the foliose lichen species Parmelina tiliacea were studied to determine responses of the photosynthetic apparatus to high temperatures in the dry and wet state. The speed with which dry thalli were activated by water following a 24 h exposure at different temperatures decreased as the temperature was increased. But even following a 24 h exposure to 50 °C the fluorescence induction kinetics OJIP reflecting the reduction kinetics of the photosynthetic electron transport chain had completely recovered within 128 min. Exposure of dry thalli to 50 °C for 24 h did not induce a K-peak in the fluorescence rise suggesting that the oxygen evolving complex had remained intact. This contrasted strongly with wet thalli were submergence for 40 s in water of 45 °C inactivated most of the photosystem II reaction centres. In wet thalli, following the destruction of the Mn-cluster, the donation rate to photosystem II by alternative donors (e.g. ascorbate) was lower than in higher plants. This is associated with the near absence of a secondary rise peak (~1 s) normally observed in higher plants. Analysing the 820 nm and prompt fluorescence transients suggested that the M-peak (occurs around 2-5 s) in heat-treated wet lichen thalli is related to cyclic electron transport around photosystem I. Normally, heat stress in lichen thalli leads to desiccation and as consequence lichens may lack the heat-stress-tolerance-increasing mechanisms observed in higher plants. Wet lichen thalli may, therefore, represent an attractive reference system for the evaluation of processes related with heat stress in higher plants.

Bu çalışma, farklı sürelerde [0 (kontrol), 1, 3 ve 5 saat] UV-B ışımasının arpa (Hordeum vulgare L., Bülbül 89) yapraklarının fotosistem II (PSII) etkinliği üzerine etkisini araştırmak için yapılmıştır. UV-B stresinin, PSII etkinliği üzerine etkisini değerlendirmek için klorofil a fluoresansındaki polifazik artış (OJIP) kullanılmıştır. UV-B stresi, arpa bitkisinin JIP-Testine göre hesaplanan fonksiyonel parametrelerini ve yapısal parametrelerini önemli düzeyde etkilemiştir. Farklı sürelerdeki UV-B’nin polifazik klorofil a fluoresansı üzerine etkisi, PSII’nin donör ve akseptör kısmının kısmi öneminin değerlendirilmesi perspektifinden tartışılmıştır

Magnesium deficiency in plants is a widespread problem, affecting productivity and quality in agriculture, yet at a physiological level it has been poorly studied in crop plants. Here, a physiological characterization of Mg deficiency in Beta vulgaris L. an important crop model, is presented. The impact of Mg deficiency on plant growth, mineral profile and photosynthetic activity was studied. The aerial biomass of plants decreased after 24 days of hydroponic culture in Mg-free nutrient solution, whereas the root biomass was unaffected. Analysis of mineral profiles revealed that Mg decreased more rapidly in roots than in shoots and that shoot Mg content could fall to 3 mg g(-1) DW without chlorosis development and with no effect on photosynthetic parameters. Sucrose accumulated in most recently expanded leaves before any loss in photosynthetic activity. During the development of Mg deficiency, the two photosystems showed sharply contrasting responses. Data were consistent with a down-regulation of PSII through a loss of antenna, and of PSI primarily through a loss of reaction centres. In each case, the net result was a decrease in the overall rate of linear electron transport, preventing an excess of reductant being produced during conditions under which sucrose export away from mature leaf was restricted., Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

Cyanobacteria have the natural ability to degrade moderate amounts of organic pollutants. However, when pollutant concentration exceeds the level of tolerance, bleaching of the cells and death occur within 24 hours. Under stress conditions, cyanobacterial response includes the short-term adaptation of the photosynthetic apparatus to light quality, named state transitions. Moreover, prolonged stresses produce changes in the functional organization of phycobilisomes and in the core-complexes of both photosystems, which can result in large changes in the PS II fluorescence yield. The localization of ferredoxin-NADP+ reductase (FNR) at the ends of some peripheral rods of the cyanobacterial phycobilisomes, makes this protein a useful marker to check phycobilisome integrity. The goal of this work is to improve the knowledge of the mechanism of action of a very potent pesticide, lindane (γ-hexaclorociclohexane), in the cyanobacteriumAnabaena sp., which can be considered a potential candidate for bioremediation of pesticides. We have studied the effect of lindane on the photosynthetic apparatus ofAnabaena using fluorescence induction studies. As ferredoxin-NADP+ reductase plays a key role in the response to oxidative stress in several systems, changes in synthesis, degradation and activity of FNR were analyzed. Immunolocalization of this enzyme was used as a marker of phycobilisome integrity. The knowledge of the changes caused by lindane in the photosynthetic apparatus is essential for rational further design of genetically-modified cyanobacteria with improved biorremediation abilities. Polyphasic chlorophylla fluorescence rise measurements (OJIP) have been used to evaluate the vitality and stress adaptation of the nitrogen-fixing cyanobacteriumAnabaena PCC 7119 in the presence of increasing concentrations of lindane. Effects of the pesticide on the ultrastructure have been investigated by electron microscopy, and FNR has been used as a marker of phycobilisome integrity. Cultures ofAnabaena sp. treated with moderate amounts of lindane showed a decrease in growth rate followed by a recovery after 72 hours of pesticide treatment. Concentrations of lindane below 5 ppm increased the photosynthetic performance and activity of the cells. Higher amounts of pesticide caused a decrease in these activities which seems to be due to a non-competitive inhibition of PS II. Active PS II units are converted into non-QA reducing, so called heat sink centers. Specific activity and amount of FNR in lindane-treated cells were similar to the values measured in control cultures. Release of FNR from the thylakoid after 48 hours of exposure to 5 ppm of lindane towards the cytoplasm was detected by immunogold labeling and electron microscopy. From these results, we conclude that the photosynthetic performance and activity of the cells are slightly increased in the presence of lindane up to 5 ppm. Moreover, in those conditions, iindane did not produce significant changes in the synthesis, degradation or activity of FNR. The high capability ofAnabaena to tolerate lindane makes this cyanobacterium a good candidate for phytoremediation of polluted areas. The results of this study show that cultures ofAnabaena PCC 7119 tolerate lindane up to 5 ppm, without significant changes in the photosynthetic vitality index of the cells. However, a slight increase in phycobiliprotein synthesis is observed, which is related to total protein content. This change might be due to degradation of proteins less stable than phycobiliproteins. An identification of the proteins with altered expression pattern in the presence of the pesticide remains the subject of further work and will provide valuable information for the preparation of strains which are highly tolerant to lindane.

The chlorophyll fluorescence kinetics of ‘Jonagold' and ‘Cox' apples, stored under different conditions to induce mealiness, were measured. Three different storage conditions were considered causing three mealiness levels: not mealy, moderately and strongly mealy. Also destructive measurements of the texture (firmness, hardness, juice content and soluble solids content) were done. Classification into different mealiness levels based on the fluorescence measurements was more performant than a classification based on the destructive measurements. To estimate the mealiness level in a non-destructive way from the fluorescence features, a number of different classifiers were constructed. Quadratic discriminants and supervised and unsupervised neural networks were tested and compared. The self-organising map gives promising results when compared with the multi-layer perceptrons and quadratic discriminant analysis. The different advantages of the constructed classifiers suggest that fluorescence can be used in an automatic sorting line to assess certain types of mealiness.

Co-inoculations of the alfalfa (Medicago sativa L.) plants with the associative- and/or the obligate nitrogen-fixing bacteria (Azospirillum brasilense, S; Rhizobium meliloti, R) and/or the vesicular arbuscular mycorrhiza fungus (Glomus fasciculatum, M) were evaluated in a pot experiment under controlled conditions. The effect of these beneficial microbes, as single- (M, R, S), dual- (MR, MS) or multilevel (MRS) inoculation-treatments were assessed in a calcareous loamy chernozem soil, originating from a grass-type natural ecosystem. A range of substrates were used to separate the influence of the indigenous microbes: C, untreated original soil (i.e. including all of the usual microflora); G, gamma-sterilised soil (no competitive microbes); GB, sterile soil (re-suspension of a mycorrhiza-free soil extract). The weight of the host, nodule-number, macro- and microelement contents and the colonisation by the inoculated bacterial and fungal microsymbionts were recorded. In the gamma-sterilised substrate all of the mono- (M), dual- (MR, MS) or multilevel (MRS) co-inoculations with the selected, Glomus fasciculatum M 107 strain were effective in improving plant growth, nutrient-uptake and abundance of the microsymbionts in the rhizosphere of alfalfa. In contrast a competition from the indigenous microflora in the non-sterilised soil, greatly reduced the functioning of the applied mycorrhizal inoculum. Although the associative Azospirillum bacteria (MS) slightly reduced effects relative to single mycorrhizal inoculation (M), the multilevel treatments, with both of the diazotrophs (MRS), showed a further enhancement (a synergistic effect) for almost all of the tested parameters and substrates. The functional compatibility of the obligate- and associative diazotrophs in the mycorhizosphere are discussed.

This paper describes a relationship between ozone exposure, biomass, visual symptoms and a chlorophyll a fluorescence performance index for young beech trees (Fagus sylvatica). The plants were exposed to four levels of ozone in open-top fumigation chambers (50, 85, 100% of ambient, and 50% of ambient+30 nl l(-1) ozone) that fluctuated in parallel with ambient ozone during a single growing season. The trees were fumigated in the four treatments with ozone levels corresponding to an AOT40 (accumulated exposure above a threshold of 40 nl l(-1)) of 0.01, 3.35, 7.06 and 19.70 microl l(-1) h, respectively. Highly significant differences were found between the 50% of ambient+30 nl l(-1) ozone treatment and all other treatments, with a 70.5% reduction in primary photosynthetic performance, as measured with the PI index. The reduction of the PI values demonstrated a high correlation with visual symptom development (r(2)=0.98), and by the end of September with biomass loss (r(2)=0.99). A significant ozone exposure-response relationship was found between AOT40 and primary photochemistry (r(2)=0.97). Thus, analysis of PI provides an alternative method for regional monitoring of tree health within the context of the currently employed AOT40.

We analysed the changes of the chlorophyll (Chl) a fluorescence rise kinetic (from 50 μs to 1 s) that occur when leaves or chloroplasts of pea ( Pisum sativum L.) are incubated under anaerobic conditions in the dark. In control leaves, Chl a fluorescence followed a typical O-J-I-P polyphasic rise [Strasser et al. (1995) Photochem Photobiol 61: 32–42]. Anaerobiosis modified the shape of the transient with the main effect being a time-dependent increase in the fluorescence yield at the J-step (2 ms). Upon prolongation of the anaerobic treatment (> 60 min), the O-J-I-P fluorescence rise was eventually transformed to an O-J (J = P) rise. A similar transformation was observed when pea leaves were treated with DCMU or sodium dithionite. Anaerobiosis resulted in a 10–20% reduction in the maximum quantum yield of the primary photochemistry of Photosystem II, as measured by the ratio of the maximal values of variable and total fluorescence (FV/FM). When the leaves were returned to the air in the dark, the shape of the fluorescence transient showed a time-dependent recovery from the anaerobiosis-induced change. The original O-J-I-P shape could also be restored by illuminating the anaerobically treated samples with far-red light but not with blue or white light. Osmotically broken chloroplasts displayed under anaerobic conditions fluorescence transients similar to those observed in anaerobically treated leaves, but only when they were incubated in a medium comprising reduced pyridine nucleotides (NADPH or NADH). As in intact leaves, illumination of the anaerobically treated chloroplasts by far-red light restored the original O-J-I-P transient, although only in the presence of methyl viologen. The results provide additional evidence for the existence of a chlororespiratory pathway in higher plant cells. Furthermore, they suggest that the J-level of the fluorescence transient is strongly determined by the redox state of the electron carriers at the PS II acceptor side.

Thylakoid membranes transferred into a low water system composed of n -octane, the cationic surfactant cetyltrimethylammonium bromide (CTAB), and 1-hexanol as cosurfactant, displayed protein- and substrate-dependent ATPase activities for more than 60 min. This activity was enhanced 7–10-fold and 3–4-fold with 28%-vol. of methanol and 21%-vol of tert -butanol present in the polar phase, respectively, in a fashion reminiscent of what occurs in aqueous media. Approximately 25% and 10% of control and methanol-enhanced ATPase activities found in buffer were detected in the low water system, respectively, and both activities showed a pronounced dependency on the amount of water present (between 2.5 and 15% of water (v/v)). 1 H-Nuclear Magnetic Resonance ( 1 H-NMR) studies revealed that the bound/free water ratio (a) increased with decreasing concentration of water in the reverse micellar phase and (b) slightly increased in the presence of methanol. The results altogether suggest that the amount and physical state of water significantly contribute to determine the ATPase activity in the low water system.

A fraction (15–20% of the total protein) of a preparation of bovine submitochondrial particles (SMPs) binds to concanavalin A–sepharose. The bound membranes displayed succinate dehydrogenase, cytochrome oxidase, and ATPase activity, which, as in SMPs, were inhibited by malonate, cyanide, and oligomycin, respectively. These results indicate that the bound membranes are inner mitochondrial membranes and that they contain a glycoprotein which was recognized by concanavalin A. It was possible to repeatedly perform the three enzyme assays, one after the other, in the same gel with the bound membranes. Long-term stability tests (22 days) showed that cytochrome oxidase was much more stable in the membranes bound to the gel than in SMPs, while the ATPase activity decayed at a similar rate in the two conditions. Thus, inner mitochondrial membranes bound to ConA–Sepharose appear to be a potentially interesting model for the study of immobilized multienzymatic complexes.

— The presence of light during exposure of intact pea leaves to high temperature (40°C) protects Photosystem II (PSII) against inactivation, as indicated by the preservation of the maximal variable 685 nm chlorophyll fluorescence and the photosynthetic oxygen evolution. This photoprotection was observed (i) to be saturated at low fluence rates (ca 10 W m-2) and (ii) to be strongly dependent on the spectral characteristics of the light. It was specifically induced by red light (630–670 nm) whereas other wavelengths were much less protective. A strong antagonism between red and far-red lights was also observed, with PSII stabilization by red light being partially cancelled by additional far-red light.

The plastoquinone (PQ) pool of the photosynthetic electron transport chain becomes reduced under anaerobic conditions. Here, anaerobiosis was used as a tool to manipulate the PQ-pool redox state in darkness and to study the effects of the PQ-redox state on the Chl-a fluorescence (OJIP) kinetics in pea leaves (Pisum sativum L.). It is shown that the F(J) (fluorescence intensity at 3 ms) is linearly related to the area above the OJ-phase (first 3 ms) representing the reduction of the acceptor side of photosystem II (PSII) and F(J) is also linearly related to the area above the JI-phase (3-30 ms) that parallels the reduction of the PQ-pool. This means that F(J) depends on the availability of oxidized PQ-molecules bound to the Q(B)-site. The linear relationships between F(J) and the two areas indicate that F(J) is not sensitive to energy transfer between PSII-antennae (connectivity). It is further shown that a approximately 94% reduced PQ-pool is in equilibrium with a approximately 19% reduction of Q(A) (primary quinone acceptor of PSII). The non-linear relationship between the initial fluorescence value (F(20 micros)) and the area above the OJ-phase supports the idea that F(20 mus )is sensitive to connectivity. This is reinforced by the observation that this non-linearity can be overcome by transforming the F(20 micros)-values into [Q(A) (-)]-values. Based on the F(J)-value of the OJIP-transient, a simple method for the quantification of the redox state of the PQ-pool is proposed.

An alternative approach to quantification of the contribution of non-QB-reducing centers to Chl a fluorescence induction curve is proposed. The experimental protocol consists of a far-red pre-illumination followed by a strong red pulse to determine the fluorescence rise kinetics. The far-red pre-illumination induces an increase in the initial fluorescence level (F(25 micros)) that saturates at low light intensities indicating that no light intensity-dependent accumulation of QA - occurs. Far-red light-dose response curves for the F(25 micros)-increase give no indication of superimposed period-4 oscillations. F(25 micros)-dark-adaptation kinetics following a far-red pre-pulse, reveal two components: a faster one with a half-time of a few seconds and a slower component with a half-time of around 100 s. The faster phase is due to the non-QB-reducing centers that re-open by recombination between QA - and the S-states on the donor side. The slower phase is due to the recombination between QB - and the donor side in active PS II reaction centers. The pre-illumination-induced increase of the F(25 micros)-level represents about 4-5% of the variable fluorescence for pea leaves ( approximately 2.5% equilibrium effect and 1.8-3.0% non-QB-reducing centers). For the other plant species tested these values were very similar. The implications of these values will be discussed.

SCOPUS: ar.j, info:eu-repo/semantics/published

In this paper we show that chlorophyll a fluorescence signals analysed with the self-organizing map (SOM) can be used as a routine tool for the monitoring and classification of pea varieties (Pisum sativum) according to their degree of resistance against drought stress. Fluorescence kinetics measurements were obtained from non-stressed plants. The aim of this study is to evaluate the applicability of artificial intelligence techniques in eco-physiological research. Our goal is to provide a fast tool that will contribute to the knowledge needed to develop strategies that would help to decrease the impact of environmental stress in agriculture and forestry. © Springer-Verlag 2003.

Chromate (Cr) decreases the growth of Spirodela polyrhiza. The fronds lost their pigments. The O2 evolution was also decreased. The Cr effect was found to be dose dependent. The toxic effects of Cr have further been studied on the photosynthetic activity of Spirodela polyrhiza by means of the chlorophyll a (Chl a) fluorescence transient O-J-I-P. The Chl a fluorescence transients were recorded in vivo with high time resolution and analyzed according to the JIP-test which can quantify the photosystem II behavior. Cr treated plants show a decrease in yield for primary photochemistry, phi Po. The performance index of PSII, PIABS, which is the combination of the indexes of three independent parameters, (1) the total number of active reaction centers per absorption (RC/ABS), (2) yield of primary photochemistry (phi Po) and (3) efficiency with which a trapped exciton can move an electron into the electron transport chain (psi 0), decreased due to Cr treatment. Chromate sensitivity varies within plant populations. In summary Cr affects several targets of PSII. More specifically, the main targets of Cr, according to the JIP-test, can be listed as a decrease in the number of active reaction centers and damage to the oxygen-evolving complex.

Several approaches have been adopted to study the role of lipids in thylakoid membrane functions. Among them, the enzymatic digestion of lipids, the use of specific antibodies against lipids, the preparation of subthylakoidal fractions and the use of mutants deficient in certain lipids have been extensively studied [1]. All these techniques have advantages and drawbacks. Recently, cyclodextrins (CD) have been reported by Rawyler and Siegenthaler [2] to remove lipids from the thylakoid membrane. CD molecules are cyclic oligosaccharides consisting of 6 (α-CD), 7 (β-CD) or 8 (γ-CD) glucopyranose units linked by α(1-4) bonds. They adopt a torus shape and are able to bind lipids within their hydrophobic cavity to form water soluble guest-CD inclusion complexes [3]. In this investigation, we have chosen, among several CD-derivatives, the PM α-CD to study the extent of lipid depletion in thylakoid membranes and the concomitant effect on the uncoupled electron flow in photosystem II (PSII) and PSI, the low temperature fluorescence spectra, the ratio F695/F740, and the fluorescence transients OJIP.

The variable chlorophyll (Chl) a fluorescence yield is related to the photochemical activity of photosystem II (PS II) of the oxygen evolving organisms. The kinetics of the fluorescence rise from the minimal yield Fo to the maximal yield Fm is a monitor of the accumulation of net reduced Qa with time in both active (Qb-containing) and inactive (non-Qb) PS II centers. The measurements of true Fo and that of the complete fluorescence transient from true Fo to Fm are useful in obtaining a kinetic picture of PS II activity. Using a shutter-less system (Plant Efficiency Analyzer, Hansatech, UK) that is capable of providing the first measured point at about 20 microseconds and that allows data accumulation over several orders of magnitude of time, we have measured the complete fluorescence transient in low and moderate (up to 700 W m-2 ) light intensities in several photosynthetic systems (higher plant leaves and chloroplasts; and the cell suspensions of green alga Chlamydomonas reinhardtii and several of its herbicide-resistant mutants, altered in single amino acids in its Dl protein). In all cases, the fluorescence transient follows a regular pattern of O-J-I-P—T, where two intermediate inflections J (at about 2 ms) and I (at about 20 ms) appear between Fo and Fm levels. Furthermore, the ratio of Fm to Fo is about 5 in all cases and the lowered published ratio in several cases is suggested to be due to the J level being mistaken for Fo. We also present data on the effects of varying the dark times between preillumination and measurements of the transient, on the intensity dependence, and on the effect of the addition of diuron. The relationship of the 0-J rise to the fast fluorescence rise observed by other investigators will also be discussed.

The dynamics of light-induced closure of the PS II reaction centers was studied in intact, dark-adapted leaves by measuring the light-irradiance (I) dependence of the relative variable chlorophyll fluorescence V which is the ratio between the amplitude of the variable fluorescence induced by a pulse of actinic light and the maximal variable fluorescence amplitude obtained with an intense, supersaturating light pulse. It is shown that the light-saturation curve of V is a hyperbola of order n. The experimental values of n ranged from around 0.75 to around 2, depending on the plant material and the environmental conditions. A simple theoretical analysis confirmed this hyperbolic relationship between V and I and suggested that n could represent the apparent number of photons necessary to close one reaction center. Thus, experimental conditions leading to n values higher than 1 could indicate that, from a macroscopic viewpoint, more than one photon is necessary to close one PS II center, possibly due to changes in the relative concentrations of the different redox states of the PS II reaction center complexes at the quasi-steady state induced by the actinic light. On the other hand, the existence of environmental conditions resulting in n noticeably lower than 1 suggests the possibility of an electron flow between PS II reaction center complexes.