Effects of Frost Hardening and Dehardening on Photosynthetic Electron Transport and Fluorescence Properties in Isolated Chloroplasts of Pinus silvestris

Photosynthetic electron transport and low-temperature fluorescence emission properties have been analyzed in isolated chloroplasts during the course of frost hardening and dehardening of Pinus silvestris L. Both the partial electron-transport reactions (H₂O DPIP and Asc./DPIP NADP) and the overall electron transport (H₂O — NAPD) showed decreasing capacities during the course of hardening. Upon exposing the plants to ?5°C and high irradiance a block in the electron-transport chain between the two photosystems developed, whereas the partial reactions still showed activities. The decrease in activity of PSl was accompanied by a decrease in P700 content, as determined by light oxidation of P700, which indicates a correlation between the two changes. Hardening also induced changes in the in vivo chlorophyll organization. During the course of hardening the fluorescence emission bands F692 and F726 decreased relative to F680. These changes were more pronounced if the plants were treated in high than in low irradiance. This suggests a greater destruction of the chlorophyll antennae in close association with the two photoreactions than in the so-called light-harvesting chlorophyll a/b antenna. During dehardening basically the reverse of the changes observed during hardening occurred. The recovery of secondary needles was complete, whereas primary needles only partly recovered.     

The Effect of Activated Charcoal on Tissue Cultures: Adsorption of Metabolites Inhibiting Morphogenesis

Cell suspensions of Daucus carota and Haplopappus gracilis and callus suspensions of Allum cepa var. proliferum were grown in media with and without activated charcoal. Differentiation occurred in those Daucus and Allium cultures that contained charcoal. It was shown by mass spectrometry that the media without charcoal contained high amounts of phenylacetic acid and p-OH-benzoic acid (Daucus), 2,6-OH-benzoic acid (Allium) and benzoic acid, pelargonic acid and caprylic acid (Haplopappus), whereas the media with activated charcoal did not. It was also shown that p-OH-benzoic acid had inhibitory effects on the embryogenesis in Daucus cultures.     

On the role of ß-carotene in the reaction center chlorophyll a antennae of photosystem I

Absorption and low temperature fluorescence emission spectra were measured on chloroplast thylakoids and on purified reaction center chlorophyll a-protein complexes of photosystem I, CP-a₁. A clear association between the presence of ß-carotene and the occurrence of far red absorbing and emitting chlorophyll a components of the reaction center antennae of photosystem I was demonstrated. For this study chloroplasts and CP-a₁ were obtained from normal and carotenoid deficient plant material of various sources. The experimental material included 1) lyophilized pea chloroplasts extracted with petroleum ether, 2) the carotenoid deficient mutant C-6E of Scenedesmus obliquus and 3) wheat chloroplasts derived from normal and SAN-9789 treated plants. Removal of carotenoids, most likely principally ß-carotene, caused a loss of long wavelength absorbing chlorophylls in chloroplasts and purified CP-a₁, and the loss or diminution of the long wavelength peak seen in the low temperature fluorescence emission spectrum. This association between ß-carotene and special chlorophyll a forms may explain both the photoprotective and antenna functions ascribed to ß-carotene. In the absence of carotenoids in wheat and in the Scenedesmus mutant, the chlorophyll a antenna of photosystem I was extremely photosensitive. A triplet-triplet resonance energy transfer from chlorophyll a to ß-carotene and a singlet-singlet energy transfer from excited ß-carotene to chlorophyll would explain the photoprotective and antenna functions, respectively. The role of this association in determining some of the fluorescence properties of photosystem I is also discussed.     

Effects of Activated Charcoal on Growth and Morphogenesis in Cell Cultures

The effects of activated charcoal on growth and morphogenesis in plate cultures of different plant cells have been studied. It was shown that medium containing charcoal induced embryogenesis in cultures of Daucus carota in which embryo formation could not be brought about by omitting auxin from the medium. Charcoal-medium also induced abundant root formation in older cultures of Allium cepa, which normally did not produce roots. The growth of cultures of Glycine max and Haplopappus gracilis was totally inhibited by charcoal. It is thought that activated charcoal removes substances from the medium, one of which might be auxin.     

Identification and characterization of 17 microsatellite primers for the tick,Ixodes ricinus,using enriched genomic libraries

Ixodes ricinus is the main vector for important infectious diseases in both humans and in animals. Microsatellite loci were isolated from a dinucleotide‐enriched library made from I. ricinus sampled in Norway. Seventeen polymorphic microsatellites were further characterized among 24 individuals sampled from an island in the Oslofjord region. The number of observed alleles ranged from two to 17 and the observed heterozygosities between 0.10 and 0.83. Analysis of family materials gives evidence of non‐Mendelian inheritance of several of the characterized loci, among which most could be explained by presence of null alleles.     

Distribution of Chlorophyll between the Two Photoreactions in Photosynthesis of the Blue-Green Alga Anacystis nidulans Grown at Two Different Light Intensities

Anacystis nidulans was grown in white light of two different intensities, 7 and 50 W ·m^?2. The in vivo pigmentations of the two cultures were compared. The ratio phycocyanin/chlorophyll a was 0.96 for cells grown at 7 W · m^?2 and 0.37 for cells grown at 50 W · m^?2. Phycocyanin-free photosynthetic lamellae (PSI-particles) were prepared, using French press treatment and fractionated centrifugation. Algae grown in the irradiance of 50 W · m^?2 showed a chlorophyll a/P700 ratio of 260, while algae grown at 7 W · m^?2 had a value of 140. Corresponding PSI-particles showed values of 122 and 109 respectively. Light-induced absorption difference spectra measured between 400–450nm indicated different ratios between cytochrome f and P700 in the two algal cultures. Enhancement studies of photosynthetic oxygen evolution were carried out. When a background beam of 691 nm was superimposed upon a signal beam of 625 nm, good enhancement was observed for both cultures. With the wavelengths 675 and 691 nm together a pronounced enhancement could be detected only in algae grown at the higher light level. Absorption spectra recorded on whole cells at 77°K revealed a small shift of the main red chlorophyll a absorption peak caused by light intensity. It is proposed that the reduction of the phycocyanin/chlorophyll a ratio in high light-grown cells is accompanied by an increased energy distribution by chlorophyll a into PSII.     

Increased growth and recruitment of piscivorous perch, Perca fluviatilis, during a transient phase of expanding submerged vegetation in a shallow lake

1. In this study, we examine how a 7‐year period of expanding submerged stonewort (Chara spp.) vegetation during a shift from turbid to clear water in a shallow lake influenced individual growth and population size structure of perch (Perca fluviatilis). We expected that a shift from phytoplankton to macrophyte dominance and clear water would improve feeding conditions for perch during a critical benthivorous ontogenetic stage, and enhance the recruitment of piscivorous perch. 2. Growth analysis based on opercula showed that growth during the second year of life was significantly higher in years with abundant vegetation than in years with turbid water and sparse vegetation. Growth was not affected during the first, third and fourth year of life. Stable isotope analyses on opercula from 2‐year‐old perch showed that the increase in growth coincided with a change in carbon source in the diet. Stable nitrogen ratio did not change, indicating that the increased growth was not an effect of any change in trophic position. 3. Following the expansion of submerged vegetation, perch size range and abundance of piscivorous perch increased in central, unvegetated areas of the lake. In stands of stoneworts, however, mainly benthivorous perch were caught, and size range did not change with time. 4. Our findings provide empirical support for the notion that establishment of submerged vegetation may lead to increased recruitment of piscivorous perch, because of improved competitive conditions for perch during the benthivorous stage. This is likely to constitute a benthic‐pelagic feedback coupling, in which submerged vegetation and clear water promote the recruitment of piscivorous perch, which, in turn, may increase water clarity through top‐down effects in the pelagic.     

Correlation of the photosystem I and II reaction center chlorophyll-protein complexes, CP-a1 and CP-aII with photosystem activity and low temperature fluorescence emission properties in mutants of Scenedesmus

Abstract Comparative studies on the low temperature fluorescence emission of whole cells, purified chlorophyll-protein (CP) complexes and on patterns noted in sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) for chlorophyll-protein complexes and chloroplast membrane polypeptides of Scenedesmus obliquus with several distinct mutant classes has allowed further correlation between the fluorescence emission bands seen at 77K and the known chlorophyll-protein complexes. In mutants deficient in photosystem II (PS-II; total loss of the reducing side) the fluorescence emission spectra showed only two peaks, i.e., 686 and 718 nm, but in the wild type, in mutants lacking the oxidizing side of PS-II and in phenotypes missing the CP-a₁ complex (and P-700 activity) all three emission bands at 686, 696 and 718 nm were present. In a mutant lacking the light-harvesting CP-a/b complex the emission peak at 686 nm was strongly reduced and the longer wavelength emissions predominated. Gel electrophoresis studies showed that the PS-II (reducing side) mutants lacked the polypeptides of apparent molecular weight 54 and 51 kilodaltons and the chlorophyll-protein complex, CP-a_II, of apparent molecular weight 32 kilodaltons. Contrarily, the loss of the oxidizing side of PS-II did not result in any alteration of these components. Genetic deletion of CP-a₁ did not alter significantly the long wavelength emission even though the isolated CP-a₁ shows the low temperature-dependent long wavelength emission comparable to that seen in the whole cell. It was deduced that remaining PS-I antennae chlorophylls must account for the emission seen at 718 nm. The absence of the CP-a/b complex and the strong simultaneous decrease of the 686 nm emission strengthens the concept that this complex is the primary emitter of fluorescence at room temperature. Its absence facilitated the detection of the CP-a_II complex in SDS-PAGE and enhanced the in vivo fluorescence by the two photosystems. Parallel experiments with two mutants which green and develop, one to the wild-type and the other to the CP-a/b deficient phenotype, provided additional evidence for the source of the low temperature emission bands.     

Partial Reversal by Cytokinin and (2-Chloroethyl)-Trimethylammonium Chloride of Near-Ultraviolet Inhibited Growth and Morphogenesis in Callus Cultures

Callus cultures of Haplopappus gracilis, Nicotiana tabacum and Allium cepa var. proliferum were in varying degrees inhibited by blue to near-UV light obtained from fluorescent tubes. The inhibition was considerably reduced for Haplopappus cultures by 6-(3-methyl-2-buten-1-ylamino)-purine (2 iP) and (2-chloro-ethyl)-trimethylammonium chloride (CCC) in combination. Even separately these compounds stimulated growth in blue but not in white light. A high concentration of 2 iP reduced the inhibiting effects of near-UV on tobacco tissue cultures, and a synergism was observed between 2 iP and CCC in respect to shoot formation in blue light. Allium callus was not significantly affected by CCC. It was also observed that the concentration of indol-3-acetic acid (IAA) was more important for the growth of tobacco cultures in blue than in white light. It is believed that the light-inhibition of growth is partly due to a photoinactivation of IAA and that 2 iP and CCC might be active through processes controlling the levels of IAA and other growth hormones.     

Sequential extraction of chlorophyll from chlorophyll-protein complexes in lyophilized pea thylakoids with solvents of different polarity

Lyophilized chloroplasts of Pisum sativum (pea) have been extracted with petroleum ether of different polarity (obtained by adding varying amounts of ethanol to the petroleum ether). Extracted thylakoids have then been solubilized by sodium dodecyl sulphate (SDS) and chlorophyll-protein complexes have been isolated by polyacrylamide gel electrophoresis (PAGE). Absorption- and low temperature fluorescence emission spectro-scopy have been used to characterize thylakoids and purified chlorophyll-protein complexes. Weakly polar solvents extracted mainly chlorophyll a. SDS-PAGE scan profiles of similarly extracted thylakoids contained no photosystem II chlorophyll a reaction center antennae (CP-a_n) and the amount of photosystem I chlorophyll a reaction center antennae (CP-a₁) was reduced as compared with an unextracted control. This was due partly to the extraction of chlorophyll a prior to SDS-PAGE, and partly to the increased solubilization of chlorophyll a by SDS as a result of β-carotene extraction. By increasing the polarity of the solvent CP-a₁ also disappeared in the scan profile, leaving only the light-harvesting chlorophyll a/b-protein complex (CP-a/b) and SDS complexed chlorophyll. From these results we conclude that the chlorophyll molecules in the reaction center antennae are relatively more hydrophobically associated than the molecules in the light-harvesting CP-a/b complex. The chlorophyll a of CP-a_u and the far red absorbing chlorophyll a fraction of CP-a₁ appear to be the most hydrophobically associated chlorophyll molecules.