Chlorophyll Fluorescence Induction Research Articles

Sunlight induced chlorophyll fluorescence in the near‐infrared spectral region in natural waters: Interpretation of the narrow reflectance peak around 761 nm

AbstractSunlight induced chlorophyll a fluorescence (SICF) can be used as a probe to estimate chlorophyll a concentrations (Chl) and infer phytoplankton physiology. SICF at ∼685 nm has been widely applied to studies of natural waters. SICF around 740 nm has been demonstrated to cause a narrow reflectance peak at ∼761 nm in the reflectance spectra of terrestrial vegetation. This narrow peak has also been observed in the reflectance spectra of natural waters, but its mechanism and applications have not yet been investigated and it has often been treated as measurement artifacts. In this study, we aimed to interpret this reflectance peak at ∼761 nm and discuss its potential applications for remote monitoring of natural waters. A derivative analysis of the spectral reflectance suggests that the 761 nm peak is due to SICF. It was also found that the fluorescence line height (FLH) at 761 nm significantly and linearly correlates with Chl. FLH(761 nm) showed a tighter relationship with Chl than the relationship between FLH(∼685 nm) and Chl mainly due to weaker perturbations by nonalgal materials around 761 nm. While it is not conclusive, a combination of FLH(761 nm) and FLH(∼685 nm) might have some potentials to discriminate cyanobacteria from other phytoplankton due to their different fluorescence responses at the two wavelengths. It was further found that reflectance spectra with a 5 nm spectral resolution are adequate to capture the spectral SICF feature at ∼761 nm. These preliminary results suggest that FLH(761 nm) need to be explored more for future applications in optically complex coastal and inland waters.

MEASUREMENT OF SUN INDUCED CHLOROPHYLL FLUORESCENCE USING HYPERSPECTRAL SATELLITE IMAGERY

Abstract. Solar Induced Chlorophyll Fluorescence (SIF), can be used as an indicator of stress in vegetation. Several scientific approaches have been made and there is considerable evidence that steady state Chlorophyll fluorescence is an accurate indicator of plant stress hence a reliable tool to monitor vegetation health status. Retrieval of Chlorophyll fluorescence provides an insight into photochemical and carbon sequestration processes within vegetation. Detection of Chlorophyll fluorescence has been well understood in the laboratory and field measurement. Fluorescence retrieval methods were applied in and around the atmospheric absorption bands 02B (Red wavelength) approximately 690 nm and 02A (Far red wavelengths) 740 nm. Hyperion satellite images were acquired for the years 2012 to 2015 in different seasons. Atmospheric corrections were applied using the 6S Model. The Fraunhofer Line Discrimanator (FLD) method was applied for retrieval of SIF from the Hyperion images by measuring the signal around the absorption bands in both vegetated and non vegetated land cover types. Absorption values were extracted in all the selected bands and the fluorescence signal was detected. The relationships between NDVI and Fluorescence derived from the satellite images are investigated to understand vegetation response within the absorption bands.

MEASUREMENT OF SUN INDUCED CHLOROPHYLL FLUORESCENCE USING HYPERSPECTRAL SATELLITE IMAGERY

Solar Induced Chlorophyll Fluorescence (SIF), can be used as an indicator of stress in vegetation. Several scientific approaches have been made and there is considerable evidence that steady state Chlorophyll fluorescence is an accurate indicator of plant stress hence a reliable tool to monitor vegetation health status. Retrieval of Chlorophyll fluorescence provides an insight into photochemical and carbon sequestration processes within vegetation. Detection of Chlorophyll fluorescence has been well understood in the laboratory and field measurement. Fluorescence retrieval methods were applied in and around the atmospheric absorption bands 02B (Red wavelength) approximately 690 nm and 02A (Far red wavelengths) 740 nm. Hyperion satellite images were acquired for the years 2012 to 2015 in different seasons. Atmospheric corrections were applied using the 6S Model. The Fraunhofer Line Discrimanator (FLD) method was applied for retrieval of SIF from the Hyperion images by measuring the signal around the absorption bands in both vegetated and non vegetated land cover types. Absorption values were extracted in all the selected bands and the fluorescence signal was detected. The relationships between NDVI and Fluorescence derived from the satellite images are investigated to understand vegetation response within the absorption bands.

Toxicological study of biofuel ethanol with blue green alga Spirulina platensis

In this study, tolerance of the blue green algal strain Spirulina platensis (Spirulina) to biofuel ethanol was investigated by monitoring algal growth, measuring respiration, photosynthetic O2 production and chlorophyll fluorescence induction with varying ethanol concentrations. Algal growth monitoring showed a dose dependent inhibitory effect of ethanol. The concentration of ethanol which inhibits algal growth by 50% (IC50) was found to be 0.36M. The rates of oxygenic photosynthesis and cellular respiration in a liquid suspension of S. platensis cells measured with a Clark-type oxygen electrode system revealed that ethanol affects both the photosynthetic apparatus and mitochondria. The ethanol IC50 value on Spirulina oxygenic photosynthesis was measured to be 1.59M. The algal chlorophyll fluorescence induction indicated that ethanol at the IC50 concentrations of 0.36M (with respect to algal growth) and 1.59M (photosynthesis) can apparently uncouple certain antenna chlorophyll pigments from the photosynthetic reaction center systems, resulting in increased background chlorophyll fluorescence. In the presence of 1.59M ethanol, the slow S to M fluorescence rise pattern appears altered, indicating that the photosynthetic excitation energy state 2 to state 1 transition in blue green algae is affected at such concentration. These results provide certain physiological insight of ethanol toxicological effects in S. platensis.

Light piping driven photosynthesis in the soil: Low-light adapted active photosynthetic apparatus in the under-soil hypocotyl segments of bean (Phaseolus vulgaris)

Photosynthetic activity was identified in the under-soil hypocotyl part of 14-day-old soil-grown bean plants (Phaseolus vulgaris L. cv. Magnum) cultivated in pots under natural light-dark cycles. Electron microscopic, proteomic and fluorescence kinetic and imaging methods were used to study the photosynthetic apparatus and its activity. Under-soil shoots at 0–2cm soil depth featured chloroplasts with low grana and starch grains and with pigment-protein compositions similar to those of the above-soil green shoot parts. However, the relative amounts of photosystem II (PSII) supercomplexes were higher; in addition a PIP-type aquaporin protein was identified in the under-soil thylakoids. Chlorophyll-a fluorescence induction measurements showed that the above- and under-soil hypocotyl segments had similar photochemical yields at low (10–55μmolphotonsm−2s−1) light intensities. However, at higher photon flux densities the electron transport rate decreased in the under-soil shoot parts due to inactivation of the PSII reaction centers. These properties show the development of a low-light adapted photosynthetic apparatus driven by light piping of the above-soil shoot. The results of this paper demonstrate that the classic model assigning source and sink functions to above- and under-soil tissues is to be refined, and a low-light adapted photosynthetic apparatus in under-soil bean hypocotyls is capable of contributing to its own carbon supply.

Effect of light intensity on chlorophyll fluorescence in wheat leaves: Application of PAM-fluorometry

Application of pulse-amplitude-modulation (PAM) fluorometers for measuring slow stages of chlorophyll fluorescence induction (CFI) is considered. With an example of Triticum aestuvum L. plants grown under continuous illumination at a photon flux density of 600 μmol/(m2 s) photosynthetically active radiation (PAR), the CFI curves were analyzed with leaves of various ages as a function of actinic light intensity. The fluorometer PAM-2100 was applied for measurements of CFI curves. The characteristic peaks of CFI curves in wheat leaves were most conspicuous and had the largest amplitudes at 600–800 μmol/(m2 s) PAR, which corresponds to the middle range of actinic light intensities employed in PAM-2100 fluorometers. In plants exposed to favorable and stressful conditions, the developmental stages may proceed at different rates; thus, the comparison of fluorescence parameters for leaves of equal calendar age but having different physiological states may provide ambiguous data. Therefore, the feasibility of recording CFI curves of different types is quite important for rapid diagnostics of the age and state of plant leaves, as well as for adequate physiological conclusions.

Modeling of primary photosynthetic processes using the kinetic Monte Carlo method

Processes that occur in the ensemble of photosynthetic electron transport systems have been modeled using a kinetic Monte Carlo method. The size of a simulated ensemble (3–5 million elementary photosynthetic chains) corresponds to the number of photosynthetic reaction centers in a plant cell. The method enables one to modify the structure of a model system according to different concepts of the organization of processes in a photosynthetic membrane. Using this model, the experimental kinetics of the chlorophyll fluorescence induction associated with the Photosystem II and the redox transformations of a photoactive pigment of the Photosystem I have been successfully reproduced. The model was verified by comparing the calculated fluorescence induction curves to experimental curves, obtained in the presence of various photosynthesis inhibitors and under temperature inactivation of the Photosystem II donor side.

Applying the Express Method of Chlorophyll Fluorescence Induction in the Studies of Cossack Juniper (Juniperus Sabina L.) "Blue Danube" Vitality in Urban Conditions in the City of Lviv

Висвітлено особливості впливу антропогенного транспортного забруднення на життєвість та декоративно-естетичні якості кущових культиварів ялівцю козацького Juniperus sabina Blue Danube, які зростають у різних умовах середовища Львова. Вивчення впливу на стан життєвості показано на прикладі функціонування пігментарного фотосинтетичного апарату хвої, яка піддається постійному впливу забруднювальних викидів автотранспорту. Дослідження зібраних зразків здійснено в лабораторних умовах із застосовуванням методу індукції флуоресценції хлорофілу, на основі заданої наукової методики.

Chlorophyll fluorescence induction kinetics and yield responses in rainfed crops with variable potassium nutrition in K deficient semi-arid alfisols

Optimum potassium (K) nutrition in semi-arid regions may help crop plants to overcome constraints in their growth and development such as moisture stress, leading to higher productivity of rainfed crops, thus judicious K management is essential. A study was conducted to evaluate the importance of K nutrition on physiological processes like photosynthesis through chlorophyll a fluorescence and chlorophyll fluorescence induction kinetics (OJIP) of rainfed crops viz., maize (Zea mays L.), pearl millet (Pennisetum glaucum), groundnut (Arachis hypogaea), sunflower (Helianthus annuus), castor (Ricinus communis L.) and cotton (Gossypium hirsutum) under water stress conditions by studying their growth attributes, water relations, yield, K uptake and use efficiency under varied K levels. Highest chlorophyll content was observed under K60 in maize and pearl millet. Narrow and wide Chl a:b ratio was observed in castor and groundnut respectively. The fluorescence yield decreased in the crops as K dosage increased, evidenced by increasing of all points (O, J, I and P) of the OJIP curves. The fluorescence transient curve for K60 was lower than K0 and K40 for all the crops. Potassium levels altered the fluorescence induction and impaired photosynthetic systems in all the crops studied. There was no distinct trend observed in leaf water potential of crops under study. Uptake of K was high in sunflower with increased rate of K application. Quantitatively, K uptake by castor crop was lesser compared to all other crops. Our results indicate that the yield reduction under low K was due to the low capacity of the crops to translocate K from non-photosynthetic organs such as stems and petioles to upper leaves and harvested organs and this in turn influenced the capacity of the crops to produce a high economic yield per unit of K taken up thus reducing utilization efficiency of K.

Effects of Soil Water Potential and Nitrogen Fertilization on Characteristics of Photosynthesis and Chlorophyll Fluorescence Induction in Schisandra chinensis Baillon

Management of soil water and fertilization is known to primarily affect physiological properties and yield in plant. The effect of soil water potential and nitrogen application on characteristics of photosynthesis and chlorophyll fluorescence in Schisandra chinensis Baillon was investigated on a sandy loam soil. Net photosyntheis rate and transpiration rate increased as a photon flux density and was highest at -50kPa of soil water potential. Light compensation point (<TEX>$1.5{\mu}molm^{-1}s^{-1}$</TEX>) and dark respiration (<TEX>$0.13{\mu}molCO_2m^{-1}s^{-1}$</TEX>) was lowest at -50 kPa but maximum photosynthesis rate (<TEX>$13.10{\mu}molCO_2m^{-1}s^{-1}$</TEX>) and net apparent quantum yield (<TEX>$0.083{\mu}molCO_</TEX><TEX>2m^{-1}s^{-1}$</TEX>) was highest at -50 kPa. As results of chlorophyll fluorescence by OJIP analysis, maximum quantum yield (Fv/Fm) of photosystem II (PSII) and PIabs was higher in treatments of -50 kPa and -60 kPa respectively, which reflects the relative reduction state of PSII. But the relative activities per reaction center such as ABS/RC and DIo/RC were low with decreasing soil water potential. Net photosyntheis rate and transpiration rate were highest at treatment of soil testing 1.0 times (<TEX>$92kgha^{-1}$</TEX>). Application of nitrogen resulted in high Fv/Fm, <TEX>$PI_{abs}$</TEX> and low ABS/RC, DIo/RC. This result implies that -50 kPa of soil water potential and nitrogen fertilizer may improve the efficiency of photosynthesis through controlling a photosystem in Schisandra chinensis Baillon.

In situ chlorophyll fluorescence kinetics as a tool to quantify effects on photosynthesis in Euphorbia cyparissias by a parasitic infection of the rust fungus Uromyces pisi.

BackgroundPhotosynthesis is the key process for plant growth and development. The determination of chlorophyll fluorescence kinetics allows the quantification of effects on photosynthetic processes triggered by environmental stress factors such as, e.g., the infection by fungal phytopathogens. The technique is non-invasive, rapid and well suited for experimental field work.ResultsHealthy and Uromyces-infected plants of Euphorbia cyparissias were monitored directly in situ in the field using rapid fluorescence kinetics. Non-infected healthy plants show a typical maximum value for the relative variable fluorescence Fv/Fm of around 0.8 with occasional variation between the leaves from the plant top towards the base, while infected plants exhibited a strong gradient to low values at the base. The photosynthetic performance index (PI) showed a higher heterogeneity within the leaves in both plant types.ConclusionsThe non-invasive and rapid measurement of chlorophyll fluorescence induction allows characterizing the photosynthetic capacity of healthy and infected plants and of parts of them directly in the field. The PI, is highly sensitive not only concerning infection, but also towards other local environmental influences.

Impact of Drought, Heat, and Their Combination on Chlorophyll Fluorescence and Yield of Wild Barley (Hordeum spontaneum)

The impact of (long-term) drought acclimation and (short-term) heat stress and their combination on fast chlorophyll fluorescence induction curves (OJIP) and grain yield was tested using pot-grown plants of wild barley (Hordeum spontaneum) originating from Northern Egypt. Concerning agronomic traits, the main effect of drought was decreased biomass accumulation and grain yield, while heat specifically affected floral development. The treatments caused specific inhibitions of photosystem II (PSII) functionality. While heat stressed plants showed a reduction of maximum quantum efficiency of PSII (φP0), an indication of effects on oxygen evolving complex (OEC) functionality, and the connectivity of PSII units, these features were entirely missing in drought acclimated plants. Drought caused a reduction of the Performance Index (PIabs) and of the relative amplitude of the IP-phase of the OJIP induction curve (ΔVIP). Individuals suffering from a combination of drought and heat showed a better ability to recover photosynthetic electron transport after the relief of stress in comparison to heat stressed plants. However, this improved capacity to recover was not accompanied by an increased grain yield. Thus, we conclude that chlorophyll fluorescence measurements provide valuable physiological data; however, their use in agronomic studies for the prediction of agronomic traits should be done with some precaution.

Drought- and frost-induced accumulation of soluble carbohydrates during accelerated senescence in Quercus pubescens

Different environmental conditions affect tree senescence by different patterns of carbohydrate concentrations and have specific impact on the dissection of the photosynthetic apparatus. A proactive cultivation of Mediterranean broadleaf species, including oaks, has been suggested to fill possible temporal and spatial gaps in forestry created by Climate Change in Central Europe in the future. Climate can affect trees in several different ways, e.g., by modulating the course of leaf senescence. Senescence-associated processes, like regulation of carbohydrates and changes in chlorophyll fluorescence under drought stress conditions were studied with leaf tissue of drought-tolerant downy oak (Quercus pubescens). Two months of consistent drought stress in a frost-free greenhouse led to significantly earlier senescence and significant increased amounts of soluble sugars in the leaves of the drought-stressed group in comparison to a well-watered control group. Similar sugar accumulation was observed in trees outdoors, after exposure to frost. In contrast to monocarpic plants the accumulation of free sugars is neither triggering leaf senescence, nor is it a side effect of age-depending changes in Q. pubescens. Instead, sugar accumulation is induced by abiotical factors, like drought and frost. Furthermore, we suggest that the senescence process in the absence of drought stress or frost depends on the source status of the leaf, which, in term, is a function of light (through photosynthesis) and night temperature (through respiration). Contents of the storage metabolite starch decreased during late summer in all three groups. Drought-stressed plants showed a decline of the connectivity of photosystem II antenna, reflected as the L-band in the chlorophyll fluorescence induction curves, and stronger correlations between the declines in the capacity of photosynthetic dark reactions and electron transport-associated chlorophyll fluorescence parameters. We conclude that the disassembly of single parts of the photosynthetic apparatus during leaf senescence is a uniform process, but the onset of this process depends on abiotical environmental factors.

The use of laser induced chlorophyll fluorescence (LIF) as a fast and non‑destructive method to investigate water deficit in Arabidopsis

Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to study the photosynthetic efficiency of plants, under control or stress conditions. Compared to most protocols of pulse amplitude modulation (PAM) fluorometry, laser induced chlorophyll fluorescence (LIF) has the advantages of not requiring pulses to be delivered at close range, allowing the remote analysis of a great number of individual plants in a short period of time. Such analyses are extremely useful, for instance, when doing large phenotyping screens of Arabidopsis thaliana mutants or ecotypes. Water deficit is a major abiotic stress compromising plant growth and productivity. Arabidopsis has been adopted as the main model organism in plant sciences and it has been widely used in plant stress studies. However, reports on the applications of LIF techniques to this model plant are scarce. Here we report the use of LIF to investigate changes in chlorophyll a (Chl a) fluorescence signature under progressive drought of potted Arabidopsis plants (Slow Stress) and under fast dehydration of detached leaves (Fast Stress). Results show that the two dehydration methods cause distinct modifications on the red/far-red Chl a fluorescence ratio (F690/F730) and on the wavelengths of Chl a fluorescence maxima. These differences are likely related to distinct changes in water content, photosynthetic pigments, anthocyanins, fatty acid composition and other metabolic adaptations, which are differently regulated in Slow and Fast Stress. Of particular interest are Chl a emission fluorescence changes, which take place under progressive drought, before a substantial decrease in leaf water content. Additionally, no differences were found on LIF emission spectra between fully expanded and young leaves. However, the choice of leaf surface influenced fluorescence emission, with the abaxial surface displaying lower fluorescence and higher F690/F730 ratios. Results suggest that LIF is a fast and non-destructive tool suitable for high-throughput phenotyping of Arabidopsis under water deficit.

Imaging of fast chlorophyll fluorescence induction curve (OJIP) parameters, applied in a screening study with wild barley (Hordeum spontaneum) genotypes under heat stress

We quantified the influence of heat stress (HS) on PSII by imaging of parameters of the fast chlorophyll fluorescence (CF) induction (OJIP) kinetic of 20 genotypes of wild barley (Hordeum spontaneum) covering a broad geographical spectrum. We developed a standardised screening procedure, allowing a repetitive fluorescence measurement of leaf segments. The impact of HS was quantified by calculating a Heat Resistance Index (HRI), derived from the decrease of the Performance Index (PI) caused by HS treatment and following recovery. For the genotype showing the lowest HRI, reduced maximum quantum yield (φP0) and increased relative variable fluorescence of the O-J phase (K-Peak) were detected after HS, whereas the basal fluorescence (F0) remained stable. An additional feature was a lowered fraction of active (QA-reducing) reaction centres (RCs). The disturbances disappeared after one day of recovery. Spatial heterogeneities of fluorescence parameters were detected, as the negative effect of HS was stronger in the leaf areas close to the leaf tip. The results of this study prove that chlorophyll fluorescence imaging (CFI) is suitable for the detection of HS symptoms and that imaging of JIP-Test parameters should be considered in future screening and phenotyping studies aiming for the characterisation of plant genotypes.

Investigating the usefulness of satellite-derived fluorescence data in inferring gross primary productivity within the carbon cycle data assimilation system

Abstract. Simulations of carbon fluxes with terrestrial biosphere models still exhibit significant uncertainties, in part due to the uncertainty in model parameter values. With the advent of satellite measurements of solar induced chlorophyll fluorescence (SIF), there exists a novel pathway for constraining simulated carbon fluxes and parameter values. We investigate the utility of SIF in constraining gross primary productivity (GPP). As a first test we assess whether SIF simulations are sensitive to important parameters in a biosphere model. SIF measurements at the wavelength of 755 nm are simulated by the Carbon-Cycle Data Assimilation System (CCDAS) which has been augmented by the fluorescence component of the Soil Canopy Observation, Photochemistry and Energy fluxes (SCOPE) model. Idealized sensitivity tests of the SCOPE model stand-alone indicate strong sensitivity of GPP to the carboxylation capacity (Vcmax) and of SIF to the chlorophyll AB content (Cab) and incoming short wave radiation. Low sensitivity is found for SIF to Vcmax, however the relationship is subtle, with increased sensitivity under high radiation conditions and lower Vcmax ranges. CCDAS simulates well the patterns of satellite-measured SIF suggesting the combined model is capable of ingesting the data. CCDAS supports the idealized sensitivity tests of SCOPE, with SIF exhibiting sensitivity to Cab and incoming radiation, both of which are treated as perfectly known in previous CCDAS versions. These results demonstrate the need for careful consideration of Cab and incoming radiation when interpreting SIF and the limitations of utilizing SIF to constrain Vcmax in the present set-up in the CCDAS system.

The induction of chlorophyll fluorescence in the leaves of maize under conditions of contamination with heavy metals

Photoinduction chlorophyll fluorescence is a modern informative method of determining the effect of heavy metals on the physiological state agrocenosis corn without damaging the plants. Changes in any link of photosynthesis result in the change of Kautsky curve type. This allows to diagnose the present state of the photosynthetic apparatus of plants under the influence of the heavy metals. During the experience we marked differences between of fluorescence of chlorophyll leaves of corn. in areas of control and ecotypes, which are contaminated with heavy metals. The peculiarity of curves forming is determined by basic kinetic parameters, that are associated with the activities of photosynthetic apparatus.Excessive accumulation of lead, zinc, cadmium in soil is accompanied by disturbances in the photosynthetic apparatus in leaves of maize both in the initial phase of development (3–4 leaves), and during the formation of maize panicle. The value of the basic parameters such as the background fluorescence (Fo), maximum fluorescence (Fm), stationary fluorescence (Fst) shows a decrease of primary processes of photosynthesis and violation of coherence reactions of the Calvin cycle. Kautsky curve, which is obtained in the variant with a 100-fold excess background had much lower peaks amplitude than others.

Chlorophyll fluorescence as an indicator of age-dependent changes in photosynthetic apparatus of wheat leaves

Wheat (Triticum sativus L.) seedlings of various ages (2- to 16-day-old plants) were used to study age-dependent changes in the chlorophyll fluorescence induction (CFI) at various light intensities during flu- orescence measurements. Plants were raised in a growth chamber using hydroponics with expanded clay, controlled environmental conditions, and 690 µmol/(m2 s) photon flux density (PFD) of photosynthetically active radiation (PAR). Parameters of CFI were determined under actinic PFD of 380, 580, 820, and 1340 µmol/(m2 s) PAR. The fifth leaf from the stem base, exposed to uniform lighting, was sampled for measurements. This leaf emerged at the plant age of 16 days. Based on fluorescence data, we calculated the maximal photochemical quantum yield of photosystem II (F v/F m), the effective photochemical quantum yield of PSII (Yield), parameters of photochemical (qP) and non-photochemical (qN and NPQ) quenching of chlorophyll fluorescence, the F p/F t ratio, and the “vitality index” (fluorescence decrease ratio, R fd). At moderate actinic PFD, applied commonly in PAM fluorometers (about 380 µmol/(m2 s)), age-dependent changes in NPQ, F p/F t, and R fd were observed. Analysis of CFI parameters in wheat leaves of different ages at PFD increasing from 380 to 820 µmol/(m2 s) revealed that R fd, NPQ, and qN are the most sensitive markers of the leaf age among all parameters tested. These suitable indicators can be used for rapid assessment of the leaf age.

Mechanism of interaction of Al3+ with the proteins composition of photosystem II.

The inhibitory effect of Al3+on photosystem II (PSII) electron transport was investigated using several biophysical and biochemical techniques such as oxygen evolution, chlorophyll fluorescence induction and emission, SDS-polyacrylamide and native green gel electrophoresis, and FTIR spectroscopy. In order to understand the mechanism of its inhibitory action, we have analyzed the interaction of this toxic cation with proteins subunits of PSII submembrane fractions isolated from spinach. Our results show that Al 3+, especially above 3 mM, strongly inhibits oxygen evolution and affects the advancement of the S states of the Mn4O5Ca cluster. This inhibition was due to the release of the extrinsic polypeptides and the disorganization of the Mn4O5Ca cluster associated with the oxygen evolving complex (OEC) of PSII. This fact was accompanied by a significant decline of maximum quantum yield of PSII (Fv/Fm) together with a strong damping of the chlorophyll a fluorescence induction. The energy transfer from light harvesting antenna to reaction centers of PSII was impaired following the alteration of the light harvesting complex of photosystem II (LHCII). The latter result was revealed by the drop of chlorophyll fluorescence emission spectra at low temperature (77 K), increase of F0 and confirmed by the native green gel electrophoresis. FTIR measurements indicated that the interaction of Al 3+ with the intrinsic and extrinsic polypeptides of PSII induces major alterations of the protein secondary structure leading to conformational changes. This was reflected by a major reduction of α-helix with an increase of β-sheet and random coil structures in Al 3+-PSII complexes. These structural changes are closely related with the functional alteration of PSII activity revealed by the inhibition of the electron transport chain of PSII.

The relationship of potato tubers chemical composition with selected physiological indicators

The paper deals with the analysis of a ten-year study on the chemical composition of tubers of forty potato cultivars and their physiological indicators. The research was carried out at the experimental station in Parczew, Poland on a podzolic soil with typical granulometric composition of sandy silty clay, using a randomized block design in four replicates. Forty potato cultivars were the subject of this study, including eight very early, seven early, nine medium early, nine medium late and seven late cultivars. The photosynthetic activity of plants was evaluated by measuring chlorophyll a and b determined in raw leaf matter by the spectrophotometric method as well as by measurements of chlorophyll fluorescence induction of potato leaves using a fluorimeter PAM-2000. Measurements of photosynthetic indicators at various stages of potato development revealed that their increase indirectly reflected the prolongation of plant growing period, which might have a direct impact on yield quality. The chemical composition was determined by standard methods used for tubers. The main objective of the study was to determine the chemical composition of potato depending on the values of chlorophyll fluorescence indicators, which will allow prediction of the chemical composition of tubers during the growing season. The obtained results allow us to predict changes in nutrient content in potato tubers based on the indicators such as: chlorophyll a and b content, minimum and maximum fluorescence yield, maximum efficiency of photosystem in dark and mean plant growth rate.