The effects of salinity (0-400 mM NaCl, marked S0, S100, S200, and S400) on growth, photosynthesis, photosystem 2 (PS2) efficiency, ion relations, and pigment contents were studied in two seashore Cakile maritima ecotypes (Tabarka and Jerba, respectively, sampled from humid and arid bioclimatic areas). Growth of Jerba plants was improved at S100 as compared to S0. Tabarka growth was inhibited by salinity at all NaCl concentrations. Leaf sodium and chloride concentrations increased with medium salinity and were higher in Jerba than in Tabarka plants. Chlorophyll content, net photosynthetic rate, stomatal conductance (gs), and intracellular CO2 concentration were stimulated at moderate salinity (S100) in Jerba plants and inhibited at higher salt concentrations in both ecotypes: gs was the most reduced parameter. The maximum quantum efficiency of PS2 (Fv/Fm), quantum yield, linear electron transport rate, and efficiency of excitation energy capture by open PS2 reaction centres showed no significant changes with increasing salt concentration in Jerba plant and were decreased in Tabarka subjected to S400. However, the efficiency of dissipation of excess photon energy in the PS2 antenna was maintained in Jerba and was increased in Tabarka plants challenged with S400. Hence the relative salt tolerance of Jerba was associated with a better ability to use Na+ and Cl- for osmotic adjustment, the absence of pigment degradation, and the concomitant PS2 protection from photodamage. and W. Megdiche ... [et al.].
A differential response to long-term ozone exposures (50 and 100 mm3 m-3) was observed in the green and white areas of variegated leaves of Hedera canariensis var. azorica L. In green tissue the photosynthetic activity was depressed via a stomatal mechanism, and in white regions no effect was observed. Chlorophyll fluorescence parameters remained unchanged in green portions, whereas in the white ones Fm and Fv/Fm significantly diminished following ozone fumigation. and G. F. Soldatini ... [et al.].
Stressful environments such as salinity, drought, and high temperature (heat) cause alterations in a wide range of physiological, biochemical, and molecular processes in plants. Photosynthesis, the most fundamental and intricate physiological process in all green plants, is also severely affected in all its phases by such stresses. Since the mechanism of photosynthesis involves various components, including photosynthetic pigments and photosystems, the electron transport system, and CO2 reduction pathways, any damage at any level caused by a stress may reduce the overall photosynthetic capacity of a green plant. Details of the stress-induced damage and adverse effects on different types of pigments, photosystems, components of electron transport system, alterations in the activities of enzymes involved in the mechanism of photosynthesis, and changes in various gas exchange characteristics, particularly of agricultural plants, are considered in this review. In addition, we discussed also progress made during the last two decades in producing transgenic lines of different C3 crops with enhanced photosynthetic performance, which was reached by either the overexpression of C3 enzymes or transcription factors or the incorporation of genes encoding C4 enzymes into C3 plants. We also discussed critically a current, worldwide effort to identify signaling components, such as transcription factors and protein kinases, particularly mitogen-activated protein kinases (MAPKs) involved in stress adaptation in agricultural plants., M. Ashraf, P. J. C. Harris., and Obsahuje bibliografii
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., H. M. Kalaji, A. Rastogi, M. Živčák, M. Brestic, A. Daszkowska-Golec, K. Sitko, K. Y. Alsharafa, R. Lotfi, P. Stypiński, I. A. Samborska, M. D. Cetner., and Obsahuje bibliografii
Groups of Actinidia deliciosa A. Chev. C.F. Liang et A.R. Ferguson var. deliciosa kiwifruit plants were subjected to soil water shortage (D), while other groups were well irrigated (I). Variations in chlorophyll (Chl) a fluorescence indices and leaf gas exchange were determined once plants were severely stressed (25 d after the beginning of the D-cycle). Daily maximum values of photosynthetic photon flux density (PPFD) were ca. 1 650 µmol(photon) m-2 s-1, while air temperatures peaked at 34.6 °C. High irradiance per se did not greatly affect the efficiency of photosystem (PS) 2, but predisposed its synergistic reduction by D co-occurrence. Fluorescence showed transient photodamage of PS2 with a complete recovery in the afternoon in both D and I plants. Upon re-watering the efficiency of PS2 was suboptimal (95 %) at day 2 after irrigation was reinitiated. At early morning of the day 5 of re-watering, photosynthesis and stomatal conductance recovered at about 95 and 80 % of I vines, respectively, indicating some after-stress effect on stomatal aperture. Once excessive photons reached PS2, the thermal dissipation of surplus excitation energy was the main strategy to save the photosynthetic apparatus and to optimize carbon fixation. The rather prompt recovery of both Chl a fluorescence indices and net photosynthetic rate during re-watering indicated that kiwifruit photosynthetic apparatus is prepared to cope with temporary water shortage under Mediterranean-type-climates. and G. Montanaro, B. Dichio, C. Xiloyannis.
Chlorophyll a fluorescence kinetics, net photosynthetic rate (PN), water relations, and photosynthetic pigment contents were studied during acclimation of in vitro grown tobacco to higher irradiance (HL; 700 μmol m-2 s-1). Plantlets were grown on medium containing sucrose in glass vessels (G-plants) or in Magenta boxes (M-plants) with better CO2 supply in the latter ones. The effect of HL was studied either (1) in plantlets grown under original in vitro conditions (closed vessels), (2) in in vitro plantlets exposed to ambient CO2 concentration (covers removed), or (3) in plantlets transplanted to ex vitro into pots with sand and nutrient solution. Higher PN, and fraction of closed photosystem 2 (PS2) centres (1 - qP), and lower content of xanthophyll cycle pigments were found in M-plants compared to G-plants. HL treatment caused photoinhibition particularly in plants kept in closed vessels. This was indicated by the decrease in the ratio of Fv/Fm and by the increase in non-photochemical quenching, 1 - qp, and content of xanthophyll cycle pigments. Better CO2 supply ensured by the removal of closure lead to the moderate reduction of symptoms of photoinhibition, although stomatal conductance (gs), transpiration rate (E), and PN were negatively affected. The main reason was the decrease in relative air humidity, which caused similar reduction of PN, E, and gs after the transfer of plantlets to ex vitro. Nevertheless, plant response to HL seemed not to be affected by any possible root injury caused by transfer to ex vitro. The differences in contents of xanthophyll cycle pigments, degree of de-epoxidation, PN, and quenching parameters between M- and G-plantlets were still significant 7 d after ex vitro transfer and HL acclimation. and Š. Semorádová, H. Synková, J. Pospíšilová.
A sample from a photograph competition of award-winning shots taken through the mobile fluorescence microscope at the Faculty of Science Charles University in Prague, arranged by students of the Bedřich Schwarzenberg´s Forestry School, Písek. and Lenka Polanská.
Al3+ significantly delayed the loss of chlorophyll (Chl), protein, and carotenoids when compared to K+ and Mg2+ during dark-induced senescence of detached primary leaves of Triticum aestivum. Thylakoid membranes isolated from Al3+ - treated leaves showed a better retention of photosystem (PS) 2, PS1, and whole chain electron transport activities than thylakoids of K+- or Mg2+-treated leaves. These ions protected the electron transport activities and restored the DCMU-dependent fluorescence increase of thylakoid membranes in a valency-dependent manner. Al3+ also delayed the change of excitation energy distribution during senescence. and D. Subhan, S. D. S. Murthy.
The clear vibrational structure of fluorescence spectrum of β-carotene in the solvent is reported for the first time at room temperature. This finding is in good agreement with recently discovered covalent 3 1Ag- new carotenoid state. The fluorescence yield of β-carotene in ionic liquid (1-methyl-3-octyloxymethylimidazolium tetrafluoroborate) is around hundred times higher than in standard solvent n-hexane. The all-trans and 15-cis β-carotene fluorescence yields in ionic liquid are 1.96±0.03 and 2.53±0.03 %, respectively. The ionic liquid is a very useful tool for modelling photosynthetic system in situ. We present the electronic absorption data of β-carotene in ionic liquids (so called neoteric solvents) with special interest in the absorption changes as a function of temperature in the range 0-90 °C (273-363 K). Ionic liquids are also very good medium for temperature study, because they are not changing up to several hundred °C and also not evaporating during heating. The relationship between spectral characteristics of β-carotene in new generation solvents with increasing and decreasing temperature is evaluated. The energy value of the ionic state 1 1Bu+ of synthetic β-carotene in ionic liquids exhibits a linear and temperature reversible dependence on temperature up to 30 °C (303 K) and up to 40 °C (313 K) for 15-cis and all-trans β-carotenes, respectively. This is valid for both 0-0 and 0-1 transitions. and G. E. Bialek-Bylka ... [et al.].
Boron deficiency induced a dramatic inhibition in sunflower plant growth, shown by a reduction in dry mass of roots and shoots of plants grown for 10 d in nutrient solution supplied with 0.02 µM B. This low B supply facilitated the appearance of brown purple pigmentation on the plant leaves over the entire growth period. Compared to B-sufficient (BS) leaves, leakage from B-deficient (BD) leaves was 20 fold higher for potassium, 38 fold for sucrose, and 6 fold for phenolic compounds. High level of membrane peroxidation was detected by measuring peroxidase activities as well as peroxidative products in BD sunflower plants. Soluble and bound peroxidase activities measured in BD thylakoid membranes were accelerated two fold compared to those detected in BS-membranes. No detectable change in soluble peroxidase activity in roots whereas a 4 fold stimulation in bound peroxidase activity was detected. Thylakoid membranes subjected to low B supply showed enhancement in lipoxygenase activity and malondialdehyde (MDA) content in parallel with 40 and 30 % decrease of linoleic and linolenic acid contents (related to total unsaturated fatty acids). A slower rate of Hill reaction activity (40 %) and a suppressed flow of electron transfer of the whole chain (30 %) were detected in BD thylakoid membranes. This reduction was accompanied with a decline in the activity of photosystem 2 shown by a diminished rate of oxygen evolution (42 %) coupled with a quenching (27.5 %) in chlorophyll a fluorescence emission spectra at 685 nm (F685). Thus B is an important element for membrane maintenance, protection, and function by minimizing or limiting production of free oxygen radicals in thylakoid membranes of sunflower leaves.