Gloiopeltis furcata (Postels & Ruprecht) J. Agardh, a macroalga, which grows in an upper, intertidal zone, can withstand drastic environmental changes caused by the periodic tides. In this study, the photosynthetic and morphological characteristics of G. furcata were investigated. The photosynthetic performance and electron flows of the thalli showed significant variations in response to desiccation and salinity compared with the control group. Both PSII and PSI activities declined gradually when the thalli were under stress. However, the electron transport rate of PSI showed still a low value during severe conditions, while the rate of PSII approached zero. Furthermore, PSI activity of the treated thalli recovered faster than PSII after being submerged in seawater. Even though the linear electron flow was inhibited by DCMU [3-(3, 4-dichlorophenyl)-1,1-dimethylurea], the cyclic electron flow could still be restored. The rate of cyclic electron flow recovery declined with the increasing time of dark treatment, which suggested that stromal reductants from starch degradation played an important role in the donation of electrons to PSI. This study demonstrated that PSII was more sensitive than PSI to desiccation and salinity in G. furcata and that the cyclic electron flow around PSI played a significant physiological role. In addition, G. furcata had branches, which were hollow inside and contained considerable quantities of funoran. These might be the most important factors in allowing G. furcata to adapt to adverse intertidal environments., L. Huan, S. Gao, X. J. Xie, W. R. Tao, G. H. Pan, B. Y. Zhang, J. F. Niu, A. P. Lin, L. W. He, G. C. Wang., and Obsahuje bibliografii
The specificity factor of Rubisco (S f) was estimated in intact leaves from the carboxylation of ribulose-1,5-bisphosphate (RuBP) at various CO2/O2 ratios. As oxygenation is calculated by the difference of the 14CO2 uptake by RuBP in the absence and presence of oxygen, it is important to choose the optimum CO2/O2 ratios. At high CO2 concentration (1,000 cm3 m-3 and higher) oxygenation consumes less than 50% RuBP but the difference of concentrations of CO2 at cell walls (Cw) and at the carboxylation centers (Cc) is 2-5% and the influence of mesophyll resistance
(rmd) is of minor importance. To accumulate large endogenous pool of RuBP, the leaves were preilluminated in the CO2- and
O2-free gas environments for 8 to 10 s. Thereafter the light was switched off and the leaves were flushed with the gas containing different concentrations of 14CO2 and O2. The specificity factor of Rubisco was calculated from the amount of the tracer taken up under different 14CO2/O2 ratios by the exhaustion of the RuBP pool. Application of 14CO2 allowed us to discriminate between the CO2 uptake and the concurrent respiratory CO2 release which proceeded at the expense of unlabelled intermediates., J. Viil, H. Ivanova, T. Pärnik., and Obsahuje bibliografii
A theory of spectra and excitation dynamics in antenna based on the notion of exciton interactions in the cyclic structures of light-harvesting pigments is reported. The theory provides an explanation for the picosecond absorbance difference spectra, the induced absorption anisotropy decay, the anomalously high bleaching valné, as well as for the fluorescence spectra, kinetics and depolarizatio
Spectral absoiptance of greenhouse tomato (Lycopersicon esculentum Milí.) canopy (sunny day, LAI = 2.54) varied between 87-89 %. Absoiptance of smáli tomato fruits was 77 % of PAR energy (spectral reflectance was 22 % and transmittance 1 %). The difíusion resistance to COj of the parenchyma extemal layer with epidermis in smáli fruits reached 25 s cm‘i and in large green fruits 75 s cm-i. At the atmospheric CO2 concentration (330 cm^ m*^) and the quantum flux density of PAR 800 pmol m'2 s'* the steady statě CO2 evolution rate was found to be slightly below its compensation value [-0.06 mg(C02) kg-i(d.m.) s-i]. The net photosynthetic rate in smail tomato fruits was 0.3 mg(C02) kg-i(d.m.) s'*, whereas in a large green tomato it reached 0.16 mg(C02) kg-i(d.m.) s’T Intemal CO2 concentration in smáli tomato frnits by the light was 2 300 cm3(C02) m-3 and in the dark 2 900 cm3(C02) m*3. Even under the optimal irradiance CO2 difíusion proceeded always from fruits to the environment.
Effects of heat pre-treatment (60 oC for 15 min) on the chlorophyll (Chl) bleaching and excitation energy transfer in thylakoids, isolated from the cucumber cotyledons, were studied by anaiysis of the overlapping absorption and the low temperature fluorescence spectra. The Chl forms C678 and C672 appeared to be the most heat-susceptible components, whereas C684 was found to be very heat-stable. Subsequent exposure of the thylakoid suspension to a high photon flux density (ca. 3 500 pmol m‘2 s'i) caused further bleaching of all the tested forms: ca. 8-20 or 2-5 % of chlorophyll was degraded duríng the initial (0-4 min) or later (4-10 min) period of irradiation, respectively. The heat pre-treatment of thylakoids led to the decrease of the 472 and 486 nm bands in Chl fluorescence excitation spectrum and the 730 nm band in the Chl fluorescence emission spectrum. The F730/F685 ratio decreased by ca. 4-, 3- or 2-fold when excited with the wavelengths of 437, 742 or 486 nm, respectively. These ratios increased by 60-90 % after 10 min irradiation with high photon flnx density.
Pathway of protochlorophyilide (Pchlide) biosynthesis, properties of Pchlide in vitro and in vivo, its in vivo localization, structure, localization and properties of the enzyme NADPH-Pchlide oxidoreductase, and phototransfonnation and dark reduction of Pchlide to chlorophyllide are reviewed.
Room temperature absorbance and 77 K fluorescence measurements were ušed in order to identity Pchlide and Chlide spectral forms involved in protochlorophyllide photoreductíon in greening leaves of barley. Pchlide55o (the subscript refers to the in vivo absorbance maximum of the pigment) is the main photoactíve Pchlide throughout the first 8 h of greening. Its photoreductíon triggers a succession of Chl(ide) spectral forms that are identícal to those normally found after photoreductíon in uitírradiated leaves. Afler an actinic radiation pulse, Chlide5g4 appears within 2 s from an intermediate at shorter wavelength and is transformed to Chlide572 in less than 2 min. The time-scale of the shifts is remarkably shorter than in unirradiated leaves, which is consistent with the acceleratíon of Chl accumulatíon during greening. Pchlide63o and Pchlide64o act as precursors of Pchlide65o during its regeneration, which exhibits a marked inhibition at temperatures above 30 °C.
The properties of chlorophyll (Chl) a and pheophytin (Pheo) a embedded in the rigid anhydrous polymer fihns, polyvinyl alcohol (PVA) and nitrocellulose (NC) are reviewed. The aggregation capability of these pigments in two matrices is characterized by absorption, fluorescence, excitation spectra combined with fluorescence lifetime and time-resolved anisotropy. The dimer creation ability for Chl a and Pheo a is strongly affected by the polymer systém ušed for investigation. The Chl a and Pheo a ability to aggregate in polymer matrices is compared. We háve been looking for a good systém suitable for the study of properties of monomeric forms when embedded in the rigid matrix on the one hand, and for the study of energy transfer between different forms of Chl molecules on the other one. Chl a, when embedded in an anhydrous PVA matrix, is in a very stable monomeric form while Pheo a molecules in this film tend to aggregate and in the NC film they exist in the monomeric form. Thus the PVA systém can be ušed as a model systém for investigation of the properties of and processes between both dimeric and monomeric structures. The NC film, however, can be ušed as a rigid matrix when only the existence of monomeric forms of the pigments is required.
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.].
Aging induced loss of chlorophyll (Chl), carotenoids (Car) and proteins was studied in suspensions of isolated wheat chloroplasts incubated in the light or dark. Faster rate of pigment loss in the light was due to photodestruction of pigments. Compared to Chl, a greater loss of Car in the light was due to photoprotective action of Car towards Chl resulting in its own destruction. The total protein content was lowered more in the light than in dark. Soluble proteins of chloroplasts declined by 36 %, whereas membrane proteins showed a loss of only 8 % after 6 d of light incubation.