Chlorophyll a fluorescence induction measured by a fluorometer with a high temperature stressed plant material shows a new K step which is a clear peak due to fast fluorescence rise and subsequent decrease of fluorescence intensity. We focused on an explanation of the decrease of fluorescence after the K step using artificial electron acceptors and donors to photosystem 2 (PS2). Addition of the artificial electron acceptors or donors suppressed the decrease of fluorescence after the K step. We suggest that the decrease mainly reflects (by more than 81 %) an energy loss process in the reaction centre of PS2 which is most probably a nonradiative charge recombination between P680+ (oxidised primary electron donor in PS2) and a negative charge stored on either Pheo- or QA- (reduced primary electron acceptor of PS2 and reduced primary quinone electron acceptor of PS2, respectively). We suggest that the energy loss process is only possible when the inhibition of both the donor and the acceptor sides of PS2 occurs. and D. Lazár, P. Pospíšil, J. Nauš.
The induction of Crassulacean acid metabolism (CAM) characterized by day/night acid fluctuation was measured in leaves from well-watered plants of Mesembryanthemum crystallinum grown in pots of four different volumes (160, 740, 2 600, and 6 500 cm^). CAM induction was dependent on soil volume: ťhe larger the pot, the later the induction took plače. Induction started when shoot water content fell to below 3 000 % of dry mass. For plants grown in the smaller pots (160-2 600 cm^) induction was linearly correlated with decreasing leaf water content. In contiast, induction was neither correlated with age nor with developmental stage of the plants. For plants grown in the largest pots leaf water content was not decreased and CAM was not induced up to week 10. Thus CAM induction is controlled environmentally rather than developmentally.
Photodynamic and photoprotective responses at different irradiances were investigated in transgenic rice (Oryza sativa) expressing Bradyrhizobium japonicum 5-aminolevulinic acid synthase (ALA-S). With high irradiance (HI) of 350 µmol m-2 s-1, transgenic lines P5 and P14 showed a decrease in contents of chlorophyll (Chl) and the chloroplast-encoded gene psbA mRNA, whereas a decrease in light-harvesting Chl-binding proteins was observed only in P14. These effects were not observed in the wild-type (WT) line treated with HI or all of the lines treated with low irradiance (LI) of 150 µmol m-2 s-1. HI resulted in a greater decrease in the quantum yield of photosystem 2 and a greater increase in non-photochemical quenching (NPQ) in the transgenic lines, particularly in P14, compared to WT. Photoprotective zeaxanthin contents increased at HI, even though carotenoid contents were lower in the transgenic lines compared to WT. When exposed to HI, superoxide dismutase greatly increased in transgenic lines P5 and P14, but peroxidase and glutathione reductase increased only in P14, in which more photodynamic damage occurred. Thus the greater expression of ALA-S in the transgenic plants developed the stronger protective functions, i.e. the increased values of NPQ and zeaxanthin, as well as more photodynamic reactions, i.e. decreased photosynthetic component and efficiency, in the photosynthetic complexes. However, the photodynamic reactions indicate that the antioxidant capacity was insufficient to cope with the severe stress triggered by photoactive porphyrins in the transgenic rice expressing ALA-S. and S. Jung ... [et al.].
Delayed chlorophyll fluorescence (DF) is 8 ligfit ímission emitted by plants, algae and photosynthetic bacteria immediately after their irradiatíon, originating ffom chlorophyll-pigment complexes and permitted by the entire entity of the photosynthetic apparatus. Although DF presents insignificant loss of energy potentially ušed in photosynthesis process, it is a very useful and non-invasive tool to study the "light phase" of photosynthesis. The review describes the DF phenomenon, offers latest theories that explain it, presents current knowledge of its kinetic behaviour, and puts speciál emphasis on its temperature dependence and eventual purpose. Finally, possible developments in future DF research are predicted.
We compared delayed fluorescence (DF) excitation spectrometry with radiocarbon (14C) technique using a monoalgal culture of Chlorella vulgaris grown under natural temperature and irradiance. This was done by monitoring the DF, in parallel to quantum efficiency (QE) and index of radiant energy utilization efficiency (Ψ) as calculated on the basis of carbon uptake measurements by radiocarbon technique. During the diurnal cycle, temperature, irradiance, and chlorophyll (Chl) contents were monitored in the algal culture that was kept in an open transparent plastic tank submerged at the surface of Lake Kinneret, Israel. The DF signal correlated with both the QE (r 2 = 0.869, p<0.01) and Ψ (r 2 = 0.977, p<0.01) during a diurnal cycle. We suggest that, besides the measurement of active Chl and phytoplankton population composition, the DF signal provides additional information on the QE and Ψ in phytoplankton population. and E. Kurzbaum, W. Eckert, Y. Z. Yacobi.
Absorption, fluorescence and delayed luminescence (in ps time range) of cyanobacterium Tolypothrix tenuis (Kutz) adapted to green (GR) and red (RR) radiation and dissolved in 15% polyvinyl alcohol Solutions were measured. Fluorescence and delayed luminescence depended on the adaptation to radiation and the wavelength of fluorescence excitation. This suggests that paths of deactivation of excitation in pigment-protein complexes present in organisms adapted to GR and RR differ.
In our earlier works, we have identified rate-limiting steps in the dark-to-light transition of PSII. By measuring chlorophyll a fluorescence transients elicited by single-turnover saturating flashes (STSFs) we have shown that in diuron-treated samples an STSF generates only F1 (< Fm) fluorescence level, and to produce the maximum (Fm) level, additional excitations are required, which, however, can only be effective if sufficiently long Δτ waiting times are allowed between the excitations. Biological variations in the half-rise time (Δτ1/2) of the fluorescence increment suggest that it may be sensitive to the physicochemical environment of PSII. Here, we investigated the influence of the lipidic environment on Δτ1/2 of PSII core complexes of Thermosynechococcus vulcanus. We found that while non-native lipids had no noticeable effects, thylakoid membrane lipids considerably shortened the Δτ1/2, from ~ 1 ms to ~ 0.2 ms. The importance of the presence of native lipids was confirmed by obtaining similarly short Δτ1/2 values in the whole T. vulcanus cells and isolated pea thylakoid membranes. Minor, lipid-dependent reorganizations were also observed by steady-state and time-resolved spectroscopic measurements. These data show that the processes beyond the dark-to-light transition of PSII depend significantly on the lipid matrix of the reaction center.
Large amounts of antibiotics and microplastics are used in daily life and agricultural production, which affects not only plant growth but also potentially the food safety of vegetables and other plant products. Fast detection of the presence of antibiotics and microplastics in leafy vegetables is of great interest to the public. In this work, a method was developed to detect sulfadiazine and polystyrene, commonly used antibiotics and microplastics, in vegetables by measuring and modeling photosystem II chlorophyll a fluorescence (ChlF) emission from leaves. Chrysanthemum coronarium L., a common beverage and medicinal plant, was used to verify the developed method. Scanning electron microscopy, transmission electron microscopy, and liquid chromatograph-mass spectrometer analysis were used to show the presence of the two pollutants in the samples. The developed kinetic model could describe measured ChlF variations with an average relative error of 0.6%. The model parameters estimated for the chlorophyll a fluorescence induction kinetics curve (OJIP) induction can differentiate the two types of stresses while the commonly used ChlF OJIP induction characteristics cannot. This work provides a concept to detect antibiotic pollutants and microplastic pollutants in vegetables based on ChlF.
The electrophoretic migration rates of several proteins of photosystem 2 particles ffom spinách were much higher iii gels containing 1 mM Ca^^ than in gels containing 1 mM ethyleneglycol-í)w(P-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA). Incubation of gels with terbium (Tb^^) and the corresponding Tb3‘'^-fluorescence were ušed to identity the Ca^^-binding proteins on the basis of selective occupation of Ca2+-binding sites with Tb^+. The 47, 43 and particularly 33 kDa polypeptides were most probably involved in Ca2+-binding.
At the grain-filling stage, net photosynthetic rate (PN), stomatal conductance (gs), and ribulose-1,5-bisphosphate carboxylation efficiency (CE) were correlated in order to find the determinant of photosynthetic capacity in rice leaves. For a flag leaf, PN in leaf middle region was higher than in its upper region, and leaf basal region had the lowest PN value. The differences in gs and CE were similar. PN, gs, and CE gradually declined from upper to basal leaves, showing a leaf position gradient. The correlation coefficient between PN and CE was much higher than that between PN and gs in both cases, and PN was negatively correlated with intercellular CO2 concentration (Ci). Hence the carboxylation activity or activated amount of ribulose-1,5-bisphosphate carboxylase/oxygenase rather than gs was the determinant of the photosynthetic capacity in rice leaves. In addition, in flag leaves of different tillers PN was positively correlated with gs, but negatively correlated with Ci. Thus gs is not the determinant of the photosynthetic capacity in rice leaves. and D.-Y. Zhang ... [et al.].