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  • photosynthesis  (212)
  • Hymenoptera  (201)
  • Springer  (413)
  • 1990-1994  (413)
  • 1920-1924
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 73 (1994), S. 289-297 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; parasitoid ; C. rubecula ; foraging behaviour ; specialist ; synomones ; infochemical use ; tritrophic interactions ; olfaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role of volatile stimuli in the long-range host-searching behaviour of the specialist parasitoidCotesia rubecula Marshall (Hymenoptera: Braconidae) was studied. Components from the plant-host-complex Brussels sprouts (Brassica oleracea L. var.gemmifera (DC.) Schulz. cv. ‘Titurel’)-Pieris rapae L. (Lepidoptera: Pieridae) were compared for their attractiveness in dual choice tests in a windtunnel. Stimuli from cabbage plants that were mechanically damaged or damaged byP. rapae caterpillars were more attractive to this parasitoid species than stimuli emitted by the host larvae or their faeces. Parasitoids preferred leaves from the plant-host-complex over artificially damaged leaves. Undamaged cabbage plants were the least attractive to the foraging females. These results indicate that in-flight searching behaviour ofC. rubecula is guided by plant-derived information and that for this specialist species more reliable and specific host-derived cues play a minor role at longer distances.
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  • 2
    ISSN: 1570-7458
    Keywords: Cruciferae ; Brassica oleracea ; tritrophic interactions ; Pieridae ; Hymenoptera ; parasitoids ; Cotesia ; kairomones ; headspace ; GC-MS ; chemical composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Headspace composition, collected from intact cabbage plants and cabbage plants infested with eitherPieris brassicae L. orP. rapae L. (Lepidoptera: Pieridae) first instar larvae, was determined by GC-MS. Twenty-one volatiles were identified in the headspace of intact plants. Twenty-two volatiles were identified in the headspace of plants infested byP. brassicae larvae, 2 of which, Z-3-hexenyl butyrate and Z-3-hexenyl isovalerate, were not detected in the headspace of either intact orP. rapae damaged plants. In the headspace of the latter, 21 compounds were identified, all of which which were also produced by intact plants. No significant quantitative differences were found between headspace composition of the plants damaged by one or the other caterpillar species. Major differences between intact and caterpillar-damaged plants in contribution to the headspace profile were revealed for hexyl acetate, Z-3-hexenyl acetate, myrcene, sabinene and 1,8-cineole. The larval endoparasitoidCotesia glomerata L. was attracted by the volatiles emanating fromB. oleracea damaged byP. brassicae first instar larvae.C. rubecula L., a specialized larval endoparasitoids ofP. rapae, was attracted by the volatiles released from theB. oleracea-P. rapae plant-host complex. This shows that cabbage plants kept under the conditions of headspace collection produce attractive volatiles for both parasitoids.
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  • 3
    Electronic Resource
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    Entomologia experimentalis et applicata 73 (1994), S. 211-220 
    ISSN: 1570-7458
    Keywords: Eurytoma amygdali ; Hymenoptera ; Eurytomidae ; host selection ; chemical stimuli ; olfactory response ; aggregation ; oviposition ; almond
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Females of the almond seed wasp,Eurytoma amygdali Enderlein (Hymenoptera, Eurytomidae), responded in an olfactometer positively to odours from almond flowers and unripe fruits, but not to almond leaf odours and odours from flowers and unripe fruits of certain other nonhostPrunus species. Males responded to none of these odours. Extracts of undamaged unripe almond fruits (using ethanol, methanol, acetone, hexane, dichloromethane, or petroleum ether) stimulated female aggregation on glass surfaces treated with these extracts; in addition, certain fruit extracts (ethanol, methanol, or acetone) stimulated oviposition. Extracts of undamaged almond leaves (ethanol, methanol, or acetone) and flowers (ethanol or methanol) also stimulated female aggregation and oviposition. Aggregation and oviposition in response to an ethanol extract of almond fruits was intense in females aged 5 to 14 days and from 12∶00 to 18∶00h (photophase between 06∶00 and 20∶00). Certain almond fruit (ethanol, methanol, acetone or hexane) and flower extracts (ethanol or methanol) also provoked female response in the olfactometer. The results strongly suggest that certain chemical stimuli emanating from parts of the almond tree play a major role in host selection and oviposition. Some of the extracts tested may be a good source for the isolation, identification and synthesis of compounds stimulating attraction, aggregation and oviposition in nature. *** DIRECT SUPPORT *** A3414024 00003
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  • 4
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    Entomologia experimentalis et applicata 70 (1994), S. 27-39 
    ISSN: 1570-7458
    Keywords: almond seed wasp ; Eurytoma amygdali ; diapause termination ; insect dormancy ; temperature ; prolonged diapause ; photoperiod ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diapausing larvae ofEurytoma amygdali Enderlein (Hymenoptera, Eurytomidae) were collected in early August and late September. They were subjected to various photoperiod and temperature regimens for up to 20 weeks, then kept at L16:D8 and 19°C for another 14 to 26 weeks for diapause to be terminated and pupation to take place. Photoperiod did not affect diapause completion. It was confirmed that the two morphologically distinct diapause stages have different temperature requirements for their completion. The first diapause stage was completed synchronously at temperatures between 16 and 19°C. A higher temperature of 26°C delayed diapause development. The second stage required lower temperatures between 4 and 10°C. Spontaneous termination of dipause was observed at constant 19°C. When applied to the first diapause stage for 20 weeks, low temperatures made the larvae refractory to subsequent intermediate temperatures. The first stage was thus maintained until a higher temperature of 26°C made the larvae regain their ability to respond to the intermediate temperatures and complete this stage. Larvae grown in Retsou almonds had a higher diapause intensity than larvae grown in Truoito almonds. The results suggest that, in nature, the high temperatures of late summer and early autumn are likely to maintain the first diapause stage. Subsequently, the less warm temperatures of autumn allow the completion of the first stage by late autumn, and the low temperatures of late autumn and of winter allow the completion of the second diapause stage by mid winter.
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  • 5
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    Entomologia experimentalis et applicata 70 (1994), S. 83-90 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; Symphyta ; Tenthredinidae ; Dineura virididorsata ; sawfly ; sex ratio ; oviposition behaviour ; mating behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sex ratios of the arrhenotokous sawflyDineura virididorsata Retz. (Hymenoptera: Tenthredinidae) are variable among populations in the field, but are biased in favour of females. We have concluded elsewhere that the sex ratios of this species cannot be satisfactorily explained by any general sex ratio model that is available. Here we present data on the different behavioural traits that are relevant to interpretation of the evolution of female-biased sex ratios under local mate competition. We report on oviposition behaviour, mating behaviour and the patterns of movement of ovipositing virgin and mated females. Our results show that adult emergence is synchronous and females will mate daily with different males (in the laboratory, at least). This would decrease the relatedness of offspring should it also take place in the field. In addition, ovipositing females (mated and virgin) leave their site of release in a relatively short time and deposit few eggs relative to their capabilities, so siblings are unlikely to be clumped. The time that virgins spend in deposition of an egg is not different from that spent by mated females, so there is no differential ‘investment’ in this regard. These behavioural observations agree with our previous conclusion that the preconditions of current sex ratio theories are not met byD. virididorsata.
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  • 6
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    Entomologia experimentalis et applicata 70 (1994), S. 121-128 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; Trichogrammatidae ; Trichogramma fuentesi ; couleur de l'hôte ; mutation récessive ; distribution ; influence de la température
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Abstract In Cuba, during its larval development inside its host egg,Trichogramma fuentesi turns its host egg either black or brown. Crossings carried out between the two forms ofT. fuentesi allowed to show that this character is determined by one locus with two alleles: Bh, dominant, colours the host black; and bh, recessive, colours the host brown. The bh allele is more frequent in the eastern region of Cuba which is also the warmest, than in the western region. We studied the evolution of frequencies of the two alleles in different experimental polymorphic populations at 23 °C and at 30 °C. In all tested conditions, bh was at a disadvantage by comparison with Bh, except at 30 °C when its initial frequency was high (90%). Thus, temperature alone should certainly not explain the maintenance of the observed polymorphism in Cuba.
    Notes: Résumé A Cuba, les oeufs hôtes parasités parTrichogramma fuentesi Torre (Hymenoptera: Trichogrammatidae) deviennent soit noirs, soit marrons. Une série de croisements entre Trichogrammes a permis de montrer que le déterminisme de ce caractère est sous la dépendance d'un locus portant deux allèles: Bh, dominant, confère une couleur noire à l'hôte; bh, récessif, confère une couleur marron. L'allèle bh étant plus fréquent dans la région orientale de Cuba, la plus chaude, nous avons suivi l'évolution des fréquences des deux allèles dans des populations expérimentales polymorphes placées à 23 °C et 30 °C. Dans toutes les conditions testées, bh a été désavantagé par rapport à Bh, sauf à 30 °C lorsque sa fréquence initiale était élevée (90%). La température n'explique donc certainement pas à elle seule le maintien du polymorphisme à Cuba.
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  • 7
    ISSN: 1572-8889
    Keywords: parasitoid ; foraging behavior ; Hymenoptera ; Cotesia ; Lepidoptera ; Pieris ; host location ; solitary ; gregarious ; specialist ; generalist
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the present study we apply a comparative approach, in combination with experimentation, to study behavior of two parasitoid species that attack caterpillar hosts with different feeding strategies (gregarious or solitary). In a semifield setup, consisting of clean cabbage plants and plants infested with one of two host species, the foraging behavior of the specialistCotesia rubecula, on obligate parasitoid of solitarily feedingPieris rapae larvae, was compared to that of the generalistCotesia glomerata, a polyphagous parasitoid of several Pieridae species (mainly the gregariously feedingPieris brassicae).Cotesia glomerata displayed equal propensity to search for and parasitize larvae of both host species. AlthoughC. glomerata exhibited a relatively plastic foraging behavior in that it searched differently under different host distribution conditions, its behavior seems more adapted to search for gregariously feeding hosts. Females exhibited a clear “area-restricted” search pattern and were more successful in finding the gregariously feeding caterpillars.Cotesia rubecula showed a higher propensity to search forP. rapae than forP. brassicae, i.e., females left the foraging setup significantly earlier when their natural hostP. rapae was not present.C. rubecula showed a more fixed foraging behavior, which seems adapted to foraging for solitarily feeding host larvae. In a setup with onlyP. rapae larvae, the foraging strategies of the two parasitoid species were quite similar. In a choice situationC. glomerata did not show a preference for one of the host species, whileCotesia rubecula showed a clear preference for its natural host species. The latter was shown by several behavioral parameters such as the number of first landings, allocation of search time, and percentage parasitization.
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  • 8
    ISSN: 1572-8889
    Keywords: host selection ; experience ; learning ; extinction ; reinforcement ; parasitoids ; Drosophila ; Leptopilina heterotoma ; Hymenoptera ; Eucoilidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The host-foraging behavior of female entomophagous parasitoids is commonly modified by positive associative learning. Typically, a rewarding experience (e.g., successful oviposition in a host) increases a female's foraging effort in a host microhabitat of the type associated with that experience. Less well understood are the effects of unrewarding experiences (i.e., unsuccessful foraging). The influence of unrewarding experience on microhabitat choice and residence time within a microhabitat was examined for the eucoilid parasitoid,Leptopilina heterotoma, in laboratory and greenhouse assays. As determined previously, females which oviposited successfully in either of two microhabitat types (fermenting apple or decaying mushroom) strongly preferred to forage subsequently on that microhabitat type. However, failure to find hosts in the formerly rewarding microhabitat caused females to reverse their preference in favor of a novel microhabitat type. The effect, though striking, was transient: within 1–2 h, the original learned preference was nearly fully restored. Similar effects of unrewarding experiences were observed with respect to the length of time spent foraging in a microhabitat. As determined previously, oviposition experience in a particular microhabitat type increased the time spent foraging in a patch of that microhabitat type. However, failure to find hosts in the patch caused the time a wasp spent in the next unoccupied patch of that type to decrease to almost nothing. In addition, there was a tendency for an unrewarding experience on a formerly rewarding microhabitat type to extend the time spent in a patch of a novel type. The function of the observed effects of unrewarding experiences is discussed.
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  • 9
    ISSN: 1572-8889
    Keywords: Hymenoptera ; Vespidae ; Vespula spp. ; foraging behavior ; chemoorientation ; social facilitation ; local enhancement ; spatial dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A series of experiments on the discovery of meat bait by scavenging workers ofV. germanica andV. maculifrons showed that workers oriented to meats by visual cues and olfactory cues. Scavening workers ofV. germanica andV. maculifrons responded positively to the sight of conspecifics at meat baits; i.e., meat with (confined) wasps received more visits than meat without wasps. This attraction to conspecific workers on meat baits provides evidence of local enhancement, in that the presence of conspecifics at meat bait directs other wasps to a particular spatial locality. Local enhancement by yellowjackets foraging for meat may contribute to the clumped distribution of worker populations noted in studies of workers captured in meat-baited traps. We hypothesize that local enhancement of foraging is a ubiquitous behavior in species of theV. vulgaris species group and may be one attribute explaining their ecological success.
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  • 10
    ISSN: 1572-8773
    Keywords: Chorella vulgaris ; acid tolerance ; ATPase ; nickel toxicity ; nutrient uptake ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This study concerns the inhibitory effects of acid pH and nickel on growth, nutrient (NO3 - and NH4 +) uptake, carbon fixation, O2 evolution, electron transport chain and enzyme (nitrate reductase and ATPase) activities of acid tolerant and wild-type strains of Chlorella vulgaris. Though a general reduction in all these variables was noticed with decreasing pH, the tolerant strain was found to be metabolically more active than the wild-type. A reduced cation (NH4 +, Na+, K+ and Ca2+) uptake, coupled with a facilitated influx of anions (NH4 +, PO4 3- and HCO3 -), suggested the development of a positive membrane potential in acid tolerant Chlorella. Nevertheless, a tremendous increase in ATPase activity at decreasing pH revealed the involvement of superactive ATPase in exporting H+ ions and keeping the internal pH neutral. A difference in Na+ and K+ efflux of the two strains at decreasing pH suggests there is a difference in membrane permeability. The low toxicity of Ni in the acid tolerant strain may be due to the low Ni uptake brought about by a change in membrane potential as well as in permeability. Hence, the development of superactive ATPase and a change in both membrane potential and permeability not only offers protection against acidity, but also co-tolerance to metals.
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  • 11
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    Journal of comparative physiology 175 (1994), S. 363-369 
    ISSN: 1432-1351
    Keywords: Hymenoptera ; Bees ; Homing ; Landmark guidance ; Distance perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Bees and wasps acquire a visual representation of their nest's environment and use it to locate their nest when they return from foraging trips. This representation contains among other features cues to the distance of near-by landmarks. We worked with two species of ground-nesting bees, Lasioglossum malachurum (Hymenoptera: Halictidae), Dasypoda hirtipes (Hymenoptera: Melittidae) and asked which cues to landmark distance they use during homing. Bees learned to associate a single cylindrical landmark with their nest's location. We subsequently tested returning bees with landmarks of different sizes and thus introduced large discrepancies between the angular size of the landmark as seen from the nest during training and its distance from the nest. The bees' search behaviour and their choice of dummy nest entrances show that both species of ground-nesting bees consistently search for their nest at the learned distance from landmarks. The influence of the apparent size of landmarks on the bees' search and choice behaviour is comparatively weak. We suggest that the bees exploit cues derived from the apparent speed of the landmark's image at their retina for distance evaluation.
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  • 12
    ISSN: 1420-9098
    Keywords: Hymenoptera ; social bees ; behavioural castes ; behaviour ; Exoneura bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Exoneura bicolor is a univoltine allodapine bee common in montane forests of southern Australia, where it exhibits a semisocial/quasisocial colony organization. Within-nest behaviour in postemergence autumn nests ofExoneura bicolor was recorded with the aim of studying behavioural specialization in pre-reproductive colonies. Ten complete colonies were transferred to purpose-built observation nests shortly before brood eclosion in late summer. Behaviour within observation nests was recorded for periods of up to 44 days after establishment, covering a period when colonies are preparing for overwintering. Dispersal of females and brood rearing do not occur at this time, although some females may become inseminated. Analyses of data using multivariate techniques indicated four distinguishable behavioural castes, designated here as Guards, Nest Absenters, Nest Modifiers and Non-recruits. This represents a higher degree of behavioural specialization than recorded to date for other allodapines. Behaviours performed by Guards and Nest Absenters are likely to involve considerable risks, but benefit the colony as a whole, so that some nestmates in prereproductive colonies exhibit altruism that frequently aids adult siblings or cousins. The males in our study were fed by females via trophallaxis and two of the males participated in nest maintenance tasks. Our results suggest that autumn colonies ofE. bicolor form well-integrated behavioural units even though brood rearing does not commence until the following spring.
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  • 13
    ISSN: 1423-0445
    Keywords: chemical communication ; queen cells ; brood pheromone ; brood recognition ; fatty acid esters ; Hymenoptera ; Apidae ; Apis mellifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Honey bee workers are able to nurse or to destroy and thus to recognize the capped queen cells containing a pupa. Fatty acid esters, especially methyl oleate, methyl palmitate and ethyl oleate were found in significant amounts on the queen pupal cuticle. Methyl oleate, the major component, along with smaller amounts of methyl linoleate and methyl linolenate, were involved in the recognition of queen cells by workers. In natural conditions of the colony, queen cells containing a paraffin pupal lure with methyl oleate were accepted 5.9 days by workers, releasing about 1.8 queen pupa equivalents during that period, when control cells (without ester) were kept only 2.1 days. Although these esters are non specific to honey bees, they are of great importance in social regulation of the honey bee colony.
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  • 14
    ISSN: 1423-0445
    Keywords: predation ; plant-insect interactions ; tritrophic level interactions ; iridoid glycosides ; catalpol ; Lepidoptera ; Nymphalidae ; Junonia coenia ; Hymenoptera ; Formicidae ; Camponotus floridanus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We investigated the role of the iridoid glycoside, catalpol, as a deterrent to the predator,Camponotus floridanus. Four laboratory colonies of this ant were offered buckeye caterpillars (Junonia coenia: Nymphalidae) raised on diets with and without catalpol. The same colonies were offered sugar-water solutions containing varying concentrations of catalpol, in both no-choice and choice tests. Regardless of diet, buckeye caterpillars appeared to be morphologically protected from predation by the ants, possibly because of their large spines or tough cuticle. However, buckeyes raised on diets with catalpol had high concentrations of catalpol in their hemolymph; extracts of this high-catalpol hemolymph proved to be an effective deterrent to the ants. When starved ants were not given the choice of food items, they were more likely to consume sucrose solutions that contained 5 mg catalpol/ml or 10 mg catalpol/ml than they were to consume solutions with 20 mg catalpol/ml. When they were given a choice of sugar solution or a sugar solution containing catalpol, the ants avoided solutions with catalpol at any of these concentrations. Ant colony responses to catalpol in sucrose solutions varied considerably over time and among colonies.
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  • 15
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    Development genes and evolution 203 (1994), S. 450-453 
    ISSN: 1432-041X
    Keywords: Athalia rosae ; Hymenoptera ; Sperm injection ; Parthenogenesis ; Chimera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mature unfertilized eggs (oocytes) dissected from the ovary of the sawfly Athalia rosae (Hymenoptera) begin parthenogenetic development if exposed to distilled water and produce haploid males. Injection of sperm into mature oocytes through the anterior pole resulted in karyogamy in a fraction of cases which developed as diploid females. No haploid-haploid chimeras due to independent participation of the injected sperm in development were produced. When sperm were injected through the posterior pole, however, fertilization never occurred but haploid-haploid chimeras were produced in a smaller fraction of cases. Both egg nucleus-derived and injected sperm-derived nuclei contributed in forming the germ cells of the chimeric males.
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  • 16
    ISSN: 1573-1561
    Keywords: Pheromone ; 3,5-dimethyl-6-(methylethyl)-3,4,5,6-tetrahydropyran-2-one ; enantiomer ; parasitoid ; Macrocentrus grandii ; Hymenoptera ; Braconidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract In a previous study we reported identification of (3R*,5S*,6R*)-3,5-dimethyl-6-(methylethyl)-3,4,5,6-tetrahydropyran-2-one as a component of the pheromone ofMacrocentrus grandii Goidanich. The lactone was present in male and female wasps, and laboratory and field bioassays demonstrated that both sources of the lactone elicit flight initiation, upwind anemotaxis, and casting in male wasps. In the present study, the synthetic (3R,5S,6R)- and (3S,5R,6S)-lactone enantiomers (RSR andSRS, respectively) were bioassayed for biological activity. In wind tunnel studies theSRS enantiomer elicited flight initiation, upwind anemotaxis, and casting by male wasps comparable to lactone derived from male and female wasps. Flight response to theRSR enantiomer averaged 14 percent of theSRS enantiomer. No specific ratio of the stereoisomers was found more attractive than theSRS enantiomer alone. Field studies demonstrated theSRS enantiomer was active alone in attracting male wasps. When paired with (Z)-4-tridecenal (a previously identified female-derived sex pheromone), theSRS enantiomer yielded a synergistic response comparable to (Z)-4-tridecenal plus female-derived lactone.
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  • 17
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    Journal of chemical ecology 20 (1994), S. 2307-2321 
    ISSN: 1573-1561
    Keywords: Polistes metricus ; Hymenoptera ; Vespidae ; cuticular hydrocarbons ; discriminant analysis ; nestmate recognition ; social wasps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The cuticular lipids ofPolistes metricus queens, workers and males from seven laboratory-maintained colonies were extracted and analyzed by combined gas chromatography-mass spectrometry. Males had higher proportions of alkenes (20.5%) in their cuticular lipids than did queens (2.3%) or workers (7.7%). Discriminant analyses of the cuticular lipid profiles of the adult wasps showed that males group separately from females. Additional analyses showed that queens group with their respective workers by colony and that queens group even more closely with males by colony. The most distinct groupings occurred with workers only by colony and with males only by colony. Stepwise discriminant analyses showed that each type of grouping was dependent upon a different combination of cuticular lipids.
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  • 18
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    Journal of chemical ecology 20 (1994), S. 2437-2453 
    ISSN: 1573-1561
    Keywords: Varroa jacobsoni ; Acari ; Varroidae ; mite ; Apis mellifera ; Hymenoptera ; Apidae ; honeybee ; chemoreception ; host selection ; cuticle ; hydrocarbons ; alkanes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The ectoparasitic miteVarroa jacobsoni invades worker brood cells of the honeybeeApis mellifera during the last 20 hr before the cells are sealed with a wax cap. Cuticle extracts of 8-day-old worker honeybee larvae occupying such brood cells have an arrestment effect on the mite. The mites run for prolonged periods on the extract, systematically returning onto the stimulus after touching the borders of the treated area. Mites increase walking speed and path straightness in response to increasing doses of a nonpolar fraction of the cuticle extract. Saturated straight-chain odd-numbered C19–C29 hydrocarbons were identified by thin-layer argentation chromatography and gas chromatography-mass spectrometry as the most active constituents, with branched alkanes also contributing to the arrestment effect of this active fraction. Analysis of the behavior responses to syntheticn-alkanes indicate that the response is probably based on a synergism between the different alkane components of the fraction rather than to an individual compound.
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  • 19
    ISSN: 1573-1561
    Keywords: Herbivory ; host preference ; host selection ; oviposition ; phenolic glucosides ; willow ; Salicaceae ; Salix ; galling sawfly ; Hymenoptera ; Tenthredinidae ; Euura amerinae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effects of phenolic glucosides on the oviposition behavior ofEuura amerinae L. (Hymenoptera: Tenthredinidae) were tested in multiple oviposition experiments using different shoot length categories ofSalix pentandra L. (with different amounts of phenolic glucosides) and in experiments with pure phenolic glucosides (salidroside, arbutin, salicin, 90% salicortin, 90% 2′-O-acetylsalicortin) or composite total fractions of phenolic glucosides from three willow species (S. pentandra, S. myrsinifolia Salisb.,S. triandra L.). This was the first time that the effects of pure phenolic glucosides on the oviposition behavior of sawfly species were tested. Total fraction of phenolic glucosides fromS. pentandra and its main individual glucoside, 2′-O-acetyl-salicortin, stimulated the strongest ovipositional behavior inE. amerinae. The results show clearly that females ofE. amerinae can recognize and choose their host willow,S. pentandra, on the basis of phenolic glucosides. Moreover, they are probably able to use phenolic glucosides as a cue in shoot selection within host-plant individuals.
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  • 20
    ISSN: 1573-5028
    Keywords: carbonic anhydrase ; antisense ; over-expression ; tobacco ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activity and location of carbonic anhydrase has been modified by transformation of tobacco with antisense and over-expression constructs. Antisense expression resulted in the inhibition of up to 99% of carbonic anhydrase activity but had no significant impact on net CO2 assimilation. Stomatal conductance and susceptibility to water stress appeared to increase in response to the decline in carbonic anhydrase activity. An over-expression construct designed to increase cytosolic carbonic anhydrase abundance resulted in a significant increase in net activity, a small increase in stomatal conductance but little impact on CO2 assimilation. Chloroplastic carbonic anhydrase activity was enhanced by the expression of an additional construct which targeted the polypeptide to the organelle. The increase in chloroplastic carbonic anhydrase appeared to be accompanied by a concomitant increase in Rubisco activity.
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  • 21
    ISSN: 1573-5028
    Keywords: gene expression ; photosynthesis ; protein turnover ; psbA ; tac promoter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI Q repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 μmol photons m-2 s-1 in the presence of 40 or 80 μg/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 μg/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI Q system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.
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  • 22
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    Journal of applied phycology 6 (1994), S. 199-210 
    ISSN: 1573-5176
    Keywords: cyanobacteria ; iron deficiency ; photosynthesis ; siderophores ; flavodoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron is an essential component of electron transport in almost all living organisms. It is particularly important to phototrophs like cyanobacteria because 22–23 irons are required for a complete functional photosynthetic apparatus. Since the low solubility of Fe+++ above neutral pH in oxic ecosystems severely limits the biological availability of iron to aquatic microorganisms, cyanobacteria and other microbes have developed a number of responses to cope with iron deficiency. Cyanobacterial responses to iron stress include the synthesis of an efficient, siderophore-based system to scavenge iron and the substitution of ferredoxin with flavodoxin. An additional response in cyanobacteria involves the alteration of the light-harvesting apparatus that includes the appearance of a new, iron-stress-induced, photosystem II, chlorophyll-binding protein. Although cytochromec-553 has a potential non-iron-containing replacement in plastocyanin, a copper-containing protein, iron stress appears to favor the utilization of cytochromec-553 because siderophores also bind copper and form a complex that is excluded from the cell. This paper is intended primarily as a review of molecular and physiological responses of actively growing cyanobacterial cultures to conditions of iron stress, where iron is present but essentially insoluble, and to differentiate these responses from iron starvation, where the amount of iron in the system is not sufficient for cell growth.
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  • 23
    ISSN: 1573-5176
    Keywords: fluorescence ; photoinhibition ; photosynthesis ; Spirulina ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorophyll fluorescence measurements were used to evaluate the effect of temperature on photoinhibition inSpirulina platensis cultures grown in tubular reactors outdoors. Cultures grown at 35 °C during the day time showed a lower reduction in the Fv/Fm ratio as compared to cultures grown at 25 °C. It is demonstrated that the lower temperature photoinhibited cells can undergo a complete recovery once transferred to low light and higher temperature. This recovery does not take place when 100 µg ml-1 chloramphenicol is added to cells. The recovery is light dependent and cells incubated in the dark at low temperature do not show a recovery in the Fv/Fm ratio. The data presented strongly support the hypothesis that photoinhibition takes place in outdoorSpirulina cultures. At the same time it is demonstrated that fluorescence measurements can be used as a fast reliable indication for photoinhibition in outdoor algal cultures.
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  • 24
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    Journal of applied phycology 6 (1994), S. 45-60 
    ISSN: 1573-5176
    Keywords: biofilter ; biofuels ; CO2 ; macroalgae ; marine biomass ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biomass production from macroalgae has been viewed as important mainly because of the need for pollution abatement. Environmental considerations will increasingly determine product and process acceptability and drive the next generation of economic opportunity. Some countries, including Japan, are actively promoting "green" technologies that will be in demand worldwide in the coming decades. Should an international agreement on CO2-reduction be ratified, its effective use for energy production would be of high priority. This report shows that macroalgae have great potential for biomass production and CO2 bioremediation. Macroalgae have high productivity, as great or greater than the most productive land plants, and do not compete with terrestrial crops for farm land. The review focuses on recent data on productivity, photosynthesis, nutrient dynamics, optimization and economics. Biomass from macroalgae promises to provide environmentally and economically feasible alternatives to fossil fuels. Nevertheless, the techniques and technologies for growing macroalgae on a large-scale and for converting feedstocks to energy carriers must be more fully developed.
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  • 25
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    Journal of applied phycology 6 (1994), S. 309-313 
    ISSN: 1573-5176
    Keywords: light source ; emission spectrum ; photosynthesis ; algae ; absorption ; efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method for quantitative evaluation of light sources from the point of their suitability for algal cultivation is described. Two parameters are used for the evaluation: (1) amount of photons emitted in the spectral region absorbed by algae per consumed unit of electrical energy; (2) fraction of photons intercept by the algae that got effectively transformed into chemical energy. The value of parameter (2) depends on the emission spectrum of the light source, the absorption spectrum of the algae, quantum capacity of the algae and on conditions of cultivation. The method permits the assessment of the differences in algal productivity under light of various light sources with respect to other recent methods for comparison.
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  • 26
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    Journal of applied phycology 6 (1994), S. 331-335 
    ISSN: 1573-5176
    Keywords: turbulence ; photosynthesis ; Chlorella ; light/dark cycles ; mass transfer rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In mass algal cultures, some form of agitation is usually provided; among other effects, this moves the organisms though an optically dense profile and provides mixing. During this transport, medium frequency fluctuations in the light energy supply are perceived by the algae, which are of the order of 1 Hz and less. It has been suggested that turbulence with the resultant light/dark cycles of medium frequency enhances productivity. However, turbulence has two major influences in a well mixed system: it facilitates fluctuating light regimes and increases the transfer rates between the growth medium and the cultured organism. An estimation of productivity as oxygen liberation was measured under laminar and turbulent flow rates, and varying light/dark ratios. Increased turbulence, which increased exchange rates of nutrients and metabolites between the cells and their growth medium, together with increased light/dark frequencies, increased productivity and photosynthetic efficiency.
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  • 27
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    Plant systematics and evolution 193 (1994), S. 173-186 
    ISSN: 1615-6110
    Keywords: Rhamnaceae ; Frangula ; Diptera ; Coleoptera ; Hymenoptera ; Mecoptera ; Breeding system ; phenology ; pollination biology ; protandry ; reproductive success ; self-incompatibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Various aspects of the reproductive biology of the perennial hermaphroditeFrangula alnus Mill. were studied in two populations located in the province of Cádiz, southern Spain. Flowering extends from the second week of May to early July. The small, whitegreenish, entomophilous flowers are incompletely protandrous and last 8–10 days, but pollen transfer takes place only on days 1–3. A very weak, pleasant odour along with nectar and pollen attract over 45 insect species, of which 21 are probable pollinators. These are mainlyDiptera but also includeHymenoptera and the unusual (as flower visitors)Mecoptera. Reproduction is exclusively sexual and strictly xenogamous, with pollen transfer depending solely on insect vectors. Although flower morphology and individual flower phenology do not fully prevent self-pollination, and geitonogamy can easily take place, the level of autogamy was negligible. Therefore, some self-incompatibility mechanism is operative in this species. Only 2.8% of open-pollinated flowers set fruit. At the flower level, fruit initiation was apparently limited by availability of cross-pollen, which in turn seemed influenced by the structure of the population. The seed/ovule ratio in ripe fruits was ca. 50%. Predispersal (maternal) reproductive success (percent ovules becoming filled seeds) was 1.42%. For mature individuals this corresponded to ca. 430 to 1560 potential offspring per year.
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  • 28
    ISSN: 1573-5036
    Keywords: photosynthesis ; osmotic adjustment ; stomatal conductance ; relative water content ; water potential ; water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Four pigeon pea [Cajanus cajan (L.) Mill sp.] cultivars were studied during two cycles of development of water stress and recovery. During these two cycles the genetic variation in vegetative development, leaf water potential, relative water content, photosynthesis, and stomatal conductance was followed. Plants were grown in a greenhouse and irrigated every seventh day. On two occasions (30 days and 80 days from sowing) water was withheld for 13 days in one group of plants and 16 days in another. Control plants were irrigated as usual. The four cultivars differed in their response to drought, with ICPL 215 being the most tolerant cultivar. In the plants exposed to the 13-day water stress, the first stress cycle resulted in preconditioning of plants such that higher values for carbon dioxide exchange rate and relative water content were observed in the second stress cycle. The longer stress period (16 days) resulted in some damage to the photosynthetic capacity and in a slow recovery rate in both cycles. During the second drought cycle the plants retained a water content above the critical value, possibly due to osmotic adjustment. It seems that water status parameters, especially relative water content, may serve as indicators of drought tolerance in pigeon pea varieties and may be useful in breeding programs for cultivation of pigeon pea under semiarid conditions.
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  • 29
    ISSN: 1573-5079
    Keywords: light conditions ; theoretical model ; barley leaf ; photosynthesis
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    Topics: Biology
    Notes: Abstract A theoretical model is presented describing the distortion of chlorophyll fluorescence spectra of a chloroplast or a group of chloroplasts by the effect of fluorescence reabsorption. Model calculations using the experimental data show that the primary reabsorption effect occurs already within one chloroplast and the spectral distortion depends significantly on the excitation regime of the chloroplast. A theoretical dependence of the distortion function, defined as a change in the F(685)/F(735) fluorescence band ratio, on the mean chlorophyll concentration in a chloroplast is predicted for different light excitation regimes. The distortion of measured chlorophyll fluorescence spectra at 77 K of chloroplast suspension adsorbed on filter papers of two strongly different diffusive reflectivities and at different mean chlorophyll concentrations are discussed with the help of the presented theory.
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  • 30
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    Photosynthesis research 39 (1994), S. 475-489 
    ISSN: 1573-5079
    Keywords: DNA repair ; flavonoids ; gene expression ; oxidative stress ; photosynthesis ; promoter
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    Topics: Biology
    Notes: Abstract Influx of solar UV-B radiation (280–320 nm) will probably increase in the future due to depletion of stratospheric ozone. In plants, there are several targets for the deleterious UV-B radiation, especially the chloroplast. This review summarizes the early effects and responses of low doses of UV-B at the molecular level. The DNA molecules of the plant cells are damaged by UV due to the formation of different photoproducts, such as pyrimidine dimers, which in turn can be combatted by specialized photoreactivating enzyme systems. In the chloroplast, the integrity of the thylakoid membrane seems to be much more sensitive than the activities of the photosynthetic components bound within. However, the decrease of mRNA transcripts for the photosynthetic complexes and other chloroplast proteins are among very early events of UV-B damage, as well as protein synthesis. Other genes, encoding defence-related enzymes, e.g., of the flavonoid biosynthetic pathway, are rapidly up-regulated after commencement of UV-B exposure. Some of the cis-acting nucleotide elements and trans-acting protein factors needed to regulate the UV-induced expression of the parsley chalcone synthase gene are known.
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  • 31
    ISSN: 1573-5079
    Keywords: photosynthesis ; electrometry ; membrane potential ; electron transfer ; charge displacement ; electrostatic ; Chloroflexus aurantiacus ; Rhodopseudomonas viridis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The thermophilic phototrophChloroflexus aurantiacus possesses a photosynthetic reaction center (RC) containing a pair of menaquinones as primary (QA) and secondary (QB) electron acceptors and a bacteriochlorophyll dimer (P) as a primary donor. A tetraheme cytochromec 554 with two high(H)- and two low(L)-potential hemes operates as an immediate electron donor for P. The following equilibrium Em,7 values were determined by ESR for the hemes in whole membrane preparations: 280 mV (H1), 150 mV (H2), 95 mV (L1) and 0 mV (L2) (Van Vliet et al. (1991) Eur. J. Biochem. 199: 317–323). Partial electrogenic reactions induced by a laser flash inChl. aurantiacus chromatophores adsorbed to a phospholipid-impregnated collodion film were studied electrometrically at pH 8.3. The photoelectric response included a fast phase of ΔΨ generation (τ 〈 10 ns, phase A). It was ascribed to the charge separation between P+ and QA − as its amplitude decreased both at high and low Eh values (Em,high=360±10 mV, estimated Em,low∼\s-160 mV) in good agreement with Em values for P/P+ and QA/QA − redox couples. A slower kinetic component appeared upon reduction of the cytochromec 554 hemes (phase C). With H1 reduced before the flash the amplitude of phase C was equal to 15–20% of that of phase A and its rise time was 1.2–1.3 μs: we attribute this phase to the electrogenic electron transfer from H1 to P+. Pre-reduction of H2 decreased the τ value to about 700–800 ns and increased the amplitude of phase C to 30–35% of that of phase A. Pre-reduction of L1 further accelerated phase C (up to τ of 500 ns) and induced a reverse electrogenic phase with τ of 12 μs and amplitude equal to 10% of phase A. Upon pre-reduction of L2 the rise time of phase C was decreased to about 300 ns and its amplitude decreased by 30%. The acceleration in the onset of phase C is explained by the acceleration of the rate-limiting H1 ⇒ P electrogenic reaction after reduction of the other hemes due to their electrostatic influence; a P-H1-(L1-L2)-H2 alignment of redox centers with an approximately rhombic arrangement of the cytochromec 554 hemes is proposed. The observed reverse phase is ascribed to the post-flash charge redistribution between the hemes. Redox titration of the amplitude of phase C yielded the Em,8.3 values of H1, H2 and L2 hemes: 340±10 mV for H1, 160±20 mV for H2 and −40±40 mV for L2.
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  • 32
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    Photosynthesis research 41 (1994), S. 175-180 
    ISSN: 1573-5079
    Keywords: Chlorobium ; Chloroflexus ; chlorophyll ; light-harvesting ; photosynthesis ; resonance Raman
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    Topics: Biology
    Notes: Abstract Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria.
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  • 33
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    Keywords: bacteriochlorophyll ; chlorosomeChlorobium limicola ; green bacteria ; photosynthesis ; monogalactosyl diglyceride
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    Topics: Biology
    Notes: Abstract Artificial aggregates of bacteriochlorophyllc (BChlc) were formed in an aqueous medium in the presence of a lipid, monogalactosyl diglyceride (MGDG), and the optical properties of those aggregates were studied by absorption and circular dichroism (CD) mainly. Four BChlc homologs, ([E,E]BChlc F, [P,E]BChlc F, [E,M]BChlc F and [I,E]BChlc F), were isolated from the green photosynthetic bacteriumChlorobium limicola strain 6230. Above 0.0004%, MGDG induced a red-shift of the absorption maxima of BChlc aggregates. At 0.003% MGDG BChlc aggregates showed absorption maxima in the range of 724 to 745 (±3) nm with a shift of 12 to 24 (±3) nm depending on the homolog species. Four kinds of BChlc-MGDG aggregates showed characteristic CD spectra. [E,M]BChlc F gave rise to a CD spectrum similar to that of chlorosomes, while the other three gave spectra of opposite sign. These aggregates are sensitive to 1-hexanol treatment; in a saturating amount (0.85%) of 1-hexanol, all the homologs gave a monomer-like absorption spectrum peaking at 670nm. At an intermediate concentration (0.5%), [E,M]BChlc F showed an enhanced CD intensity, as observed in native chlorosomes. Resonance Raman spectra of the monomer-like BChlc samples indicated that the keto vibrational band at ca. 1640 cm−1 was considerably weakened by the 0.85% 1-hexanol treatment, however the 1680 cm−1 band characteristic of a free keto group did not appear. These results indicate that the artificial aggregates formed by purified BChlc homologs and MGDG are good models for studying chlorosomes structure.
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  • 34
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    Photosynthesis research 39 (1994), S. 201-204 
    ISSN: 1573-5079
    Keywords: automatic determination ; fluorescence parameters ; fluorometer ; induction curve ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The (Fpl-Fo)/Fv value of the fluorescence induction curve is shown to be a more suitable parameter to detect a wider range of heat stress damage to thylakoid membranes as compared to quantities t 1/2 (time of fluorescence rise from Fo to (Fo+Fm)/2 level) and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaacq% aHepaDaaaaaa!39D5!\[\overline \tau \] (the fluorescence induction time defined as the area above the induction curve normalized to Fv=1). A method for exact and automatic Fpl determination is presented. A break point in the quality and behaviour of the fluorescence induction curve of barley leaves incubated at 49°C was reached at the moment (about 240 s) when the transformation of PS II active (QB-reducing) to PS II inactive (QB-non-reducing) centres was completed. The meaning of the standard Fv and Fv/Fm parameter was then changed. The method of Fpl determination described here may help to increase the analytical value of the standard chlorophyll fluorometers.
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  • 35
    ISSN: 1573-5079
    Keywords: chlorosis ; diagnostic ; flavodoxin ; iron-limitation ; photosynthesis ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron supply has been suggested to influence phytoplankton biomass, growth rate and species composition, as well as primary productivity in both high and low NO3 − surface waters. Recent investigations in the equatorial Pacific suggest that no single factor regulates primary productivity. Rather, an interplay of bottom-up (i.e., ecophysiological) and top-down (i.e., ecological) factors appear to control species composition and growth rates. One goal of biological oceanography is to isolate the effects of single factors from this multiplicity of interactions, and to identify the factors with a disproportionate impact. Unfortunately, our tools, with several notable exceptions, have been largely inadequate to the task. In particular, the standard technique of nutrient addition bioassays cannot be undertaken without introducing artifacts. These so-called ‘bottle effects’ include reducing turbulence, isolating the enclosed sample from nutrient resupply and grazing, trapping the isolated sample at a fixed position within the water column and thus removing it from vertical movement through a light gradient, and exposing the sample to potentially stimulatory or inhibitory substances on the enclosure walls. The problem faced by all users of enrichment experiments is to separate the effects of controlled nutrient additions from uncontrolled changes in other environmental and ecological factors. To overcome these limitations, oceanographers have sought physiological or molecular indices to diagnose nutrient limitation in natural samples. These indices are often based on reductions in the abundance of photosynthetic and other catalysts, or on changes in the efficiency of these catalysts. Reductions in photosynthetic efficiency often accompany nutrient limitation either because of accumulation of damage, or impairment of the ability to synthesize fully functional macromolecular assemblages. Many catalysts involved in electron transfer and reductive biosyntheses contain iron, and the abundances of most of these catalysts decline under iron-limited conditions. Reductions of ferredoxin or cytochrome f content, nitrate assimilation rates, and dinitrogen fixation rates are amongst the diagnostics that have been used to infer iron limitation in some marine systems. An alternative approach to diagnosing iron-limitation uses molecules whose abundance increases in response to iron-limitation. These include cell surface iron-transport proteins, and the electron transfer protein flavodoxin which replaces the Fe-S protein ferredoxin in many Fe-deficient algae and cyanobacteria.
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  • 36
    ISSN: 1573-5079
    Keywords: photosynthesis ; membrane protein ; protein structure ; light harvesting
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    Topics: Biology
    Notes: Abstract We have used antibodies generated against synthetic peptides to determine the topology of the 43 kD chlorophyll a binding protein (CP 43) of Photosystem II. Based on the pattern of proteolytic fragments detected (on western blots) by peptide specific antibodies, a six transmembrane span topological model, with the amino and carboxyl termini located on the stromal membrane surface, is predicted. This structure is similar to that predicted for CP 47, a PS II chlorophyll a binding protein (Bricker T (1990) Photosynth Res 24: 1–13). The model is discussed in reference to the possible location of chlorophyll binding sites.
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  • 37
    ISSN: 1573-5036
    Keywords: crop growth ; gas exchange ; minirhizotrons ; nutrients ; photosynthesis ; respiration ; rhizotron ; root observation ; root growth ; water balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A research facility is described for the integrated study of soil-root-shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight below-ground compartments aligned along a corridor. A rain shelter automatically covers the experimental area at the start of rainfall. Compartments are 125 cm × 125 cm and 200 cm deep. Each compartment has a separate drip irrigation system. Crop canopy photosynthesis, respiration, and transpiration can be measured simultaneously and continuously on four out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth. Multiple sensors for measuring soil moisture status, electrical conductivity, temperature, soil respiration, trace gases and oxygen are installed in spatial patterns in accordance with the requirements of the experiments. Sensors are connected to control and data-acquisition devices. Likewise, provisions have been made to sample manually the soil solution and soil atmosphere. Root observation tubes (minirhizotrons) are installed horizontally at depth intervals ranging from 5 cm (upper soil layers) to 25 cm (below 1 m). The facility is at present in use to study growth and development of vegetation (crops) in relation to drought, nutrient status, soil-borne diseases, and underground root competition. One important application is the study of elevated CO2 concentration and climate change and the way they affect crops and their carbon economy. Growth and development of field grown vegetables and winter cover crops are also evaluated. The common aspect of those studies is to gain a better understanding of crop growth under varying environmental conditions, and to collect datasets that may help to improve mechanistic crop growth simulation models that can address suboptimal growth conditions.
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  • 38
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    Photosynthesis research 39 (1994), S. 389-400 
    ISSN: 1573-5079
    Keywords: elevated CO2 ; nitrogen supply ; photosynthesis ; acclimation ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A common observation in plants grown in elevated CO2 concentration is that the rate of photosynthesis is lower than expected from the dependence of photosynthesis upon CO2 concentration in single leaves of plants grown at present CO2 concentration. Furthermore, it has been suggested that this apparent down regulation of photosynthesis may be larger in leaves of plants at low nitrogen supply than at higher nitrogen supply. However, the available data are rather limited and contradictory. In this paper, particular attention is drawn to the way in which whole plant growth response to N supply constitutes a variable sink strength for carbohydrate usage and how this may affect photosynthesis. The need for further studies of the acclimation of photosynthesis at elevated CO2 in leaves of plants whose N supply has resulted in well-defined growth rate and sink activity is emphasised, and brief consideration is made of how this might be achieved.
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  • 39
    ISSN: 1573-5117
    Keywords: Ruppia drepanensis ; ammonia toxicity ; temperature effects ; photosynthesis ; growth
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    Notes: Abstract In a laboratory experiment, Ruppia drepanensis Tineo seedlings from a brackish marsh in Southern Spain were grown at 20 and 30 °C, at three different nitrogen levels. These levels were obtained by the addition of a slow release fertilizer (23% NH4NO3 by weight) to a sediment mixture of sand and clay (3:1). Several morphometric parameters were recorded during the first five weeks of the experiment, and photosynthesis and respiration were measured after 7 weeks of growth. Results showed a significant reduction of growth and development with increasing nitrogen and temperature levels. Dark respiration increased strongly at high nitrogen levels. At the same time, net photosynthesis at 250 and 500 µE m-2 s-1, Pm, Km and LCP were not affected by either factor. We attribute these phenomena to ammonia toxicity, since relatively high total ammonia (NH3 + NHf4 p+) levels were found in the interstitial water.
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  • 40
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    Hydrobiologia 289 (1994), S. 65-72 
    ISSN: 1573-5117
    Keywords: photosynthesis ; selective environments ; resuspension ; disturbance ; rivers ; shallow lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factors affecting phytoplankton productivity are analysed in turbid systems, such as shallow lakes and rivers. When resuspension from the sediment or loading from the catchment significantly increases inorganic (non-algal) turbidity and hence light attenuation potentials for high production are not realised. Energy available for phytoplankton growth is strongly regulated by underwater light availability which depends on the critical mixing depth, fluctuating light intensities and algal circulation patterns. Higher production rates in shallow waters are often compensated by greater algal respiration due to higher water temperatures when compared to deeper lakes. Total daily integral production of turbulent, turbid environments can be predicted from a combination of easily measured variables such as maximum photosynthetic rates, algal biomass, surface irradiance and some measure of underwater light attenuation.
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  • 41
    ISSN: 1573-5087
    Keywords: homobrassinolide ; irrigated ; membrane stability ; moisture-stress ; nitrate reductase activity ; photosynthesis ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Homobrassinolide (BR) was applied either as a seed treatment or foliar spray to two contrasting wheat varieties, viz. C306 (drought tolerant) and HD2329 (drought susceptible), to examine its effects on plant metabolism and grain yield under irrigated and moisture-stress/rainfed conditions. BR application resulted in increased relative water content, nitrate reductase activity, chlorophyll content and photosynthesis under both conditions. BR application also improved membrane stability (lower injury). These beneficial effects resulted in higher leaf area, biomass production, grain yield and yield related parameters in the treated plants. All the treatments were significantly better than the untreated control. Generally, 0.05 ppm either as a seed treatment or foliar spray was more effective than the 0.01 ppm treatment. The drought-tolerant genotype C306 showed more response to BR application under moisture-stress/rainfed condition than HD 2329. Increased water uptake, membrane stability and higher carbon dioxide and nitrogen assimilation rates under stress seemed to be related to homobrassinolide-induced drought tolerance.
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  • 42
    ISSN: 1573-5117
    Keywords: potamoplankton ; regulated river ; transport of carbon and nutrients ; photosynthesis ; respiration ; dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ecological importance of the River Meuse phytoplankton with regard to carbon and nutrient transport has been examined in two reaches of the Belgian course of the river. Field measurements of total particulate organic carbon (POC), particulate organic nitrogen (PON) and particulate phosphorus (PP) show that the large autochtonous production of organic matter strongly affects the carbon and nutrient budget of the aquatic system. During the growing season, phytoplankton accounts for nearly 60% of the POC and dominates the PON. Calculations of the carbon and oxygen budget in the upper reach of the Belgian Meuse demonstrates that the ecosystem is autotrophic, i.e. that autochtonous FPOM (fine particulate organic matter) production is the major carbon input. This suggests that in large lowland rivers, primary production (P) may exceed community respiration (R), i.e. P:R〉1, whereas they are assumed to be heterotrophic (P:R〈1) in the River Continuum concept. The question of maintenance of phytoplankton in turbid mixed water columns is also addressed, and the case of the River Meuse is treated on the basis of studies of photosynthesis and respiration (ETS measurements). The results suggest that the potamoplankton may show some low-light acclimation, through an increase of chlorophyll a relative to biomass, when it comes to deep downstream reaches, and that algal respiration rate may be reduced. A simulation of the longitudinal development of the algal biomass shows the different phases of algal growth and decline along the river and brings support to the ‘importation hypothesis’ for explaining maintenance of potamoplankton in the downstream reaches.
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  • 43
    ISSN: 1573-5079
    Keywords: photosynthesis ; ascorbate peroxidase ; Mehler reaction ; cyclic PS I ; chlorophyll fluorescence ; 9-aminoacridine fluorescence
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    Topics: Biology
    Notes: Abstract Simultaneous measurements of 9-aminoacridine (9-AA) fluorescence quenching, O2-uptake and chlorophyll fluorescence of intact spinach chloroplasts were carried out to assess the relationship between the transthylakoidal ΔpH and linear electron flux passing through Photosystem II. Three different types of O2-dependent electron flow were investigated: (1) Catalysed by methyl viologen; (2) in the absence of a catalyst and presence of an active ascorbate peroxidase (Mehler-peroxidase reaction); (3) in the absence of a catalyst and with the ascorbate peroxidase being inhibited by KCN (Mehler reaction). The aim of this study was to assess the relative contribution of ΔpH-formation which is not associated with electron flow through Photosystem II and, which should reflect Photosystem I cyclic flow under the different conditions. The relationship between the extent of 9-AA fluorescence quenching and O2-uptake rate was found to be almost linear when methyl viologen was present. In the absence of methyl viologen (Mehler reaction) an increase of 9-AA fluorescence quenching to a value of 20% at low light intensities was associated with considerably less O2-uptake than in the presence of methyl viologen, indicating the involvement of cyclic flow. These findings are in agreement with a preceding study of Kobayashi and Heber (1994). However, when no KCN was added, such that the complete Mehler-peroxidase reaction sequence was operative, the relationship between 9-AA fluorescence quenching and the flux through PS II, as measured via the chlorophyll fluorescence parameter ΔF/Fm′ × PAR, was identical to that observed in the presence of methyl viologen. Under the assumption that methyl viologen prevents cyclic flow, it is concluded that there is no significant contribution of cyclic electron flow to ΔpH-generation in intact spinach chloroplasts.
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  • 44
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    Journal of chemical ecology 20 (1994), S. 2743-2749 
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Symphyta ; Tenthredinidae ; predation ; chemical defense ; ants ; Formicidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Evidence is presented from predation tests with ants (Formica exsectoides) that the slimy coating ofCaliroa cerasi and the waxy investiture ofEriocampa ovata serve in defense.
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  • 45
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Alloxystidae ; hyperparasitoids ; ants ; Formicidae ; interactions ; aggression ; chemical defense ; 6-methyl-5-hepten-2-one ; actinidin ; biological significance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Foraging females of the aphid hyperparasitoidAlloxysta brevis were attacked by honeydew-collecting workers of the antLasius niger at the first encounter. However, ants abandoned their attacks quickly, and foragingA. brevis remained unmolested for a subsequent time interval of approximately 5 min, which is long enough for the hyperparasitoid to oviposit successfully. Furthermore, freshly killed intactA. brevis were disregarded by ants, while decapitated specimens were readily removed. We present evidence thatA. brevis females release a mandibular gland secretion, which contains 6-methyl-5-hepten-2-one, actinidin, and unidentified iridoids, in response to an ant attack. This secretion functions both as a measure of self-defense if the female is seized by an ant worker and as a repellent, which prevents ant attacks during subsequent encounters. This is the first evidence for chemical defense in a hymenopterous parasitoid. It enablesA. brevis females to hyperparasitize ant-attended aphids that constitute a major proportion of their hosts and significantly reduces mortality by ectohyperparasitoids.
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  • 46
    ISSN: 1573-1561
    Keywords: Chemical communication ; nestmate recognition ; role of the queen ; colony closure ; aggressive behavior ; pheromone ; cuticular hydrocarbons ; ant ; Messor barbarus ; Hymenoptera ; Formicidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The results of laboratory experiments carried out with both monogynous and artificially polygynousMessor barbarus ant colonies (which under natural conditions are always monogynous) have shown that the workers belonging to monogynous colonies were able to discriminate between intruders from other monogynous colonies and those from polygynous (di- and trigynous) ones. What mechanisms are involved in this discriminatory ability? Since differences in the relative proportions of the hydrocarbons they carry are known to convey complex messages that are used for recognition purposes, it was proposed here to investigate whether there existed any differences in the proportions of the various hydrocarbons carried by the diverse categories of intruders tested in our experiments. It emerged that one set of hydrocarbons, which were usually present in rather small proportions and included all the families that constitute this species' chemical signature (n-alkanes, mono-, di-, and trimethylalkanes), was characteristically associated with workers from monogynous colonies. Another set of hydrocarbons, which included some of the above components, mostly in larger relative proportions, can be said to have characterized the digynous and trigynous colonies.
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  • 47
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    Journal of chemical ecology 20 (1994), S. 785-802 
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Agaonidae ; evolution ; fig wasps ; host finding ; volatile attractants ; Ficus ; Moraceae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Fig wasps (Chalcidoidea; Agaonidae) are intimately associated with the 750 or so species of fig trees (Ficus, Moraceae). Each tree species is usually pollinated by a single species of wasp belonging to the subfamily Agaoninae, while other wasps of the family are parasitoids or seed predators. Previous experiments have shown that the wasps are attracted to the trees by volatiles emanating from the figs. Using fig-bearing trees and arrays of sticky traps baited with figs, we investigated the specificity of wasp attraction and its timing. The pollinators of two closely relatedFicus species were specifically attracted to figs of their host species and only at the time when figs were ready to be pollinated. Some nonpollinating fig wasps appear to respond to the same volatile cues.
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  • 48
    ISSN: 1573-1561
    Keywords: Amblyomma variegatum ; Acarina ; Ixodidae ; dermal glands ; Solenopsis geminata ; Hymenoptera ; Formicidae ; defensive secretion ; entomopathogenic bacteria ; antibiotic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract When they are mechanically disturbed, all instars of the tropical bont tickAmblyomma variegatum exude droplets of a liquid on the dorsal, lateral, and ventral cuticle. These spread out and quickly evaporate. In this study, the possible role of these secretions was investigated in relation to predators and pathogens. In laboratory bioassays, it was demonstrated that the secretions from engorged larvae, nymphs, and females have an antibiotic activity against the bacteria speciesBacillus thuringiensis andSerratia marcescens, combined with a repellent effect on a potential predator, the fire-antSolenopsis geminata.
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  • 49
    ISSN: 1573-1561
    Keywords: Lepidoptera ; Pieridae ; Hymenoptera ; Braconidae ; cabbage ; Brussels sprouts ; behavior ; tritrophic interactions ; green-leaf volatiles ; herbivore-induced synomones ; elicitor ; caterpillar regurgitant ; Brassica oleracea ; Pieris brassicae ; Cotesia glomerata ; parasitoid ; wasp
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Induction of plant defense in response to herbivory includes the emission of synomones that attract the natural enemies of herbivores. We investigated whether mechanical damage to Brussels sprouts leaves (Brassica oleracea var.gemmifera) is sufficient to obtain attraction of the parasitoidCotesia glomerata or whether feeding byPieris brassicae caterpillars elicits the release of synomones not produced by mechanically damaged leaves. The response of the parasitoidCotesia glomerata to different types of simulated herbivory was observed. Flight-chamber dual-choice tests showed that mechanically damaged cabbage leaves were less attractive than herbivore-damaged leaves and mechanically damaged leaves treated with larval regurgitant. Chemical analysis of the headspace of undamaged, artificially damaged, caterpillar-infested, and caterpillar regurgitant-treated leaves showed that the plant responds to damage with an increased release of volatiles. Greenleaf volatiles and several terpenoids are the major components of cabbage leaf headspace. Terpenoids are emitted in analogous amounts in all treatments, including undamaged leaves. On the other hand, if the plant is infested by caterpillars or if caterpillar regurgitant is applied to damaged leaves, the emission of green-leaf volatiles is highly enhanced. Our data are in contrast with the induction of more specific synomones in other plant species, such as Lima bean and corn.
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  • 50
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Formicidae ; army ants ; Dorylinae ; Aenictus ; Dorylus ; Eciton ; Ecitoninae ; Dufour gland ; mandibular gland ; postpygidial gland ; ant secretions ; chemotaxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The Dufour glands ofAenictus rotundatus contain a complex mixture of terpenoids with geranylgeraniol comprising over 50% of the secretion. Some novel compounds have been tentatively identified as higher homologs of 1,3,3-trimethyl-2,7-dioxabicyclo[2,2,1]heptane based on GC-MS data. The Dufour gland secretion ofA. rotundatus is more similar in composition to the secretions of members of the subfamily Ecitoninae than to its closer relatives from the tribe Dorylini, a result that further complicates studies on the phylogeny of army ants. The mandibular glands ofA. rotundatus contain a mixture of 4-methyl-3-heptanone and limonene in trace amounts, and the well-developed postpygidial glands contain methyl anthranilate only.
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  • 51
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    Journal of chemical ecology 20 (1994), S. 969-978 
    ISSN: 1573-1561
    Keywords: Artemisinin ; arteannuic acid ; photosynthesis ; respiration ; chlorophyll ; Lemna minor
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The effects of artemisinin and arteannuic acid extracted fromArtemisia annua on the physiology ofLemna minor were evaluated. Changes in frond production, growth, dry weight, and chlorophyll content ofL. minor were determined. Photosynthesis and respiration were evaluated with a differential respirometer. Artemisinin (5 µM) inhibitedL. minor frond production and dry weight 82 and 83%, relative to methanol controls. Chlorophyll content was reduced 44% by artemisinin (2.5 µM). Arteannuic acid (10 µM) was less active, inhibiting frond production 61% and reducing chlorophyll content 66% at 5 µM. Artemisinin (1 µM) reducedL. minor photosynthesis 30% and 2.5 µM reduced respiration 39%. Arteannuic acid had no significant effect on photosynthesis or respiration at the levels tested.
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  • 52
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    Journal of chemical ecology 20 (1994), S. 1053-1056 
    ISSN: 1573-1561
    Keywords: Honey bee ; Apis mellifera ; Hymenoptera ; Apidae ; pheromone ; attractant ; Nasonov ; swarms ; citral ; geraniol ; nerolic acid ; geranic acid
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A crossover experimental design was established to test the attractancy of Nasonov pheromone to reproductive swarms of honey bees. Nineteen swarms were attracted to artificial nest cavities containing a slow-release blend of the Nasonov components citral, geraniol, and nerolic + geranic acids, and only four swarms were attracted to pheromone-free artificial nests. The results indicate that Nasonov pheromone plays a key role in the attraction of honey bee swarms to nest cavities.
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  • 53
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    Journal of chemical ecology 20 (1994), S. 1113-1119 
    ISSN: 1573-1561
    Keywords: Hymenoptera ; Formicidae ; Reptilia ; Amphisbaenidae ; Blanus cinereus ; prey odor ; harmful prey ; tongue-flicking
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We tested the ability of amphisbaenians (Blanus cinereus) to discriminate between odors of ant species selected as prey (Pheidole pallidula) and odors of potentially harmful ant species (Messor barbarus) that are avoided. Tongue-flick rate to swabs impregnated with ant odors, cologne, or deionized water differed among treatments, showing that amphisbaenians were able to discriminate ant species odors. Amphisbaenians showed an aggressive response and bit applicators bearing the odor of harmful ants, while the odor of prey ants did not elicit bites to swabs. The possible evolutionary advantage of identifying and avoiding harmful ants is discussed in relation to the fossoriality of amphisbaenians.
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  • 54
    ISSN: 1573-1561
    Keywords: Polistes fuscatus ; Hymenoptera ; Vespidae ; cuticular hydrocarbons ; discriminant function analysis ; nestmate recognition ; social wasps
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The cuticular chemicals of 124 individual wasps (foundresses and workers) from 23 colonies ofPolistes fuscatus were analyzed. The compounds identified, all of which were hydrocarbons, were similar to those of other vespid wasps in that the bulk of the hydrocarbons were 23–33 carbons in chain length. However, the hydrocarbon profile ofP. fuscatus differed from those of its congeners in its proportions of straight-chain alkanes, methylalkanes, and alkenes. Three of the 20 identified hydrocarbons, 13- and 15-MeC31, 11,15- and 13,17-diMeC31, and 13-, 15-, and 17-MeC33, had properties postulated for recognition pheromones: colony specificity, efficacy in assigning wasps to the appropriate colony, heritability, lack of differences between foundresses and workers, and distinctive stereochemistry.
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  • 55
    ISSN: 1573-1561
    Keywords: Trail pheromone ; Hymenoptera ; Formicidae ; methyl 4-methylpyrrole-2-carboxylate ; poison gland
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    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The trail pheromone ofAcromyrmex subterraneus subterraneus consists simply of the heterocyclic ester methyl 4-methylpyrrole-2-carboxylate in the venom reservoir of workers at about 1.2 ng/ant. No pyrazines were detected, and no enhancement of trail-following was observed when pyrazines were added to the pyrrole compound.
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  • 56
    ISSN: 1573-1561
    Keywords: Cotesia rubecula ; Hymenoptera ; Braconidae ; Lepidoptera ; Pieridae ; Plutellidae ; Pieris rapae ; Brassica oleracea ; Plutella xylostella ; Phaselus vulgaris ; Geranium molle ; tritrophic interactions ; infochemicals ; volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The role of airborne infochemicals in host selection by the parasitoidCotesia rubecula (Marshal) (Hymenoptera: Braconidae) was examined in a wind tunnel. To elucidate the role of volatile chemicals in attractingC. rubecula to cabbage infested by the host [Pieris rapae L. (Lepidoptera: Pieridae)], the potential sources of volatiles related toP. rapae infestation on cabbage were tested individually. The responses of females to nonhost plant species, bean and geranium, as well as to frass of a nonhost lepidopteran were also examined.C. rubecula was attracted to cabbage previously infested byP. rapae and to frass and regurgitate ofP. rapae. No attraction was observed to larvae ofP. rapae alone. Females were also attracted to mechanically damaged cabbage, cabbage previously infested byPlutella xylostella L. (Lepidoptera: Plutellidae) (a nonhost lepidopteran herbivore), and cabbage previously infested by snails (a nonhost, noninsect herbivore). Intact cabbage, bean, and geranium plants elicited no attraction. A low frequency of attraction was observed to mechanically damaged bean and geranium. Attraction was also observed to frass ofP. xylostella. Volatiles from cabbage related to damage, and volatiles from frass and regurgitate of the host seem to play an important role in guidingC. rubecula to plants infested by its host.
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  • 57
    ISSN: 1573-1561
    Keywords: Cotesia rubecula ; Hymenoptera ; Braconidae ; Lepidoptera ; Pieridae ; Plutellidae ; Pieris rapae ; Plutella xylostella ; Helix aspera ; Brassica oleracea ; Phaseolus vulgaris ; tritrophic interactions ; synomones ; infochemicals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The responses of the parasitoidCotesia rubecula to differently damaged cabbages were recorded during a series of choice tests. To determine if flyingC. rubecula can discriminate differences in the blend of volatiles emitted by cabbages damaged by different causes and how plant volatiles released from a distant source affect the searching behavior ofC. rubecula once searching on a plant, wasps were presented with a choice of plants located one behind the other and separated by a distance of 15 cm. The sources of damage were: cabbage damaged by the host (Pieris rapae), by a nonhost lepidopteran herbivore (Plutella xylostella), by a nonhost, noninsect herbivore (snail), and by mechanical means. The results showed that the site of first landing and the time spent searching on the leaves was influenced by the type of damage inflicted on plants. Wasps preferred to land on cabbages damaged by host and nonhost species of Lepidoptera over those damaged by snails and mechanical means. No preference was observed for first landing between cabbages damaged by the two species of Lepidoptera or between cabbages damaged by snails and mechanical means. Cabbage damaged byP. rapae was searched most intensively, followed by cabbage damaged byP. xylostella, cabbage damaged by snails, and cabbage damaged by mechanical means.C. rubecula differentiates between the volatile blends emitted by differently damaged cabbages, and it is attracted to volatiles related to recent lepidopteran damage. Wasps searched longer on freshly damaged than on leaves with older damage.
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  • 58
    ISSN: 1573-1561
    Keywords: Galleria mellonella ; Apis mellifera ; Pyralidae ; Apidae ; Lepidoptera ; Hymenoptera ; greater wax moth ; honeybee ; propolis ; plant resins ; phenolics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Bee propolis is a sticky amalgamation of plant resins collected by honeybees (Apis mellifera L.) and used in the hive for filling cracks and repairing combs. Propolis contains a diversity of compounds of plant origin, and is reported to have medicinal, antimicrobial, insecticidal, and phytotoxic properties. We examined the physical and chemical composition of North American samples of bee propolis from several sites in North America and tested for bioactivity against larvae of the greater wax moth (Galleria mellonella L.), a common apiary pest. The amount of methanol-extractable resin in samples from Ohio and Georgia ranged from 24% to 79% by weight. Propolis collected from hives in Ohio was more chemically diverse (over 30 compounds detected by paper chromatography) than material from south Georgia (fewer than 10 major compounds) and contained a lower proportion of methanol-insoluble beeswax. The paper chromatographic surveys revealed little variation in the chemical profile of specific hives over a six-month period and no differences between propolis from adjacent hives. Four flavonoids were identified from propolis collected in Ohio: kaempferol, galangin, 3,3′-dimethoxyquercetin and 3-methoxykaempferol. When mixed into artificial diet, fractionated propolis reduced larval growth of the greater wax moth, but not dramatically. An array of phenolics reported from propolis (caffeic acid, chrysin, ferulic acid, galangin, kaempferol, and quercetin) were bioassayed individually for effects on larvae, but none reduced larval growth at the concentrations tested, suggesting that wax moths are tolerant of some phenolics in their diet.
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  • 59
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    Journal of chemical ecology 20 (1994), S. 1583-1594 
    ISSN: 1573-1561
    Keywords: Ovipositional stimulants ; Catolaccus grandis ; Hymenoptera ; Pteromalidae ; short-chain hydrocarbons ; artificial diet ; kairomones ; synomones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Oviposition behavior was elicited fromCatolaccus grandis (Burks) (Hymenoptera: Pteromalidae) females, an ectoparasitoid of the boll weevil,Anthonomus grandis Boheman (Coleoptera: Curculionidae), by smears of freshly cut cotton bolls or smears of extracts prepared with boll weevil damaged or undamaged cotton boll tissues. Oviposition behavior was also elicited fromC. grandis females by smears made withn-pentane,n-hexane,n-heptane, and isooctane. This is the first report of oviposition behavior elicited for any parasitoid by these short-chain saturated hydrocarbons (alkanes), introducing a new concept on the chemical mediation of parasitoid behavior during host selection. Oviposition behavior was also elicited fromC. grandis females by volatiles emanating from an artificial diet devoid of insect components that was specifically developed for the in vitro rearing of ectoparasitoids. The possible use of a synergistic combination ofn-hexane and diet to optimize the mechanized production of noncontaminated eggs is also discussed.
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  • 60
    ISSN: 1573-1561
    Keywords: Pieris rapae ; Lepidoptera ; Pieridae ; Plutellidae ; Plutella xylostella ; Cotesia rubecula ; Hymenoptera ; Braconidae ; Brassica oleracea capitata ; infochemicals ; plant volatiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract To elucidate the identity of the volatile compounds that could be involved in the searching behavior of the parasitoidCotesia rubecula Marshall (Hymenoptera: Braconidae), the volatiles released by cabbage and frass of Lepidoptera feeding on cabbage were collected and analyzed using a gas chromatograph-mass spectrometer. The volatiles emitted by intact cabbage were α-pinene, β-pinene, myrcene, 1,8-cineole,n-hexyl acetate,cis-3-hexen-1-yl acetate, and dimethyl trisulfide. Mechanical damage on an intact plant induced the release of two more compounds,trans-2-hexenal and 1-methoxy-3-methylene-2-pentanone. Current feeding by larvae ofPieris rapae L. (Pieridae) induced the plant to release all the compounds released after mechanical damage and additionally 4-methyl-3-pentenal and allyl isothiocyanate. Current feeding by larvae ofPlutella xylostella L. (Plutellidae) induced the plant to release all the compounds present after mechanical damage and additionally allyl isothiocyanate. The volatiles emitted after feeding by the lepidopterans had ceased were the same as those emitted by cabbage damaged by mechanical means. The blend of volatiles emitted by frass was comprised of plant chemicals, mainly sulfur compounds. Frass ofP. rapae emitted allyl isothiocyanate, methyl isothiocyanate, methyl propyl sulfide, dimethyl trisulfide,S-methyl methane thiosulfinate, 4-methyl-3-pentenal,trans-2-hexenal, and 2,3-dihydro-4-methyl furan. Frass ofP. xylostella emitted only dimethyl trisulfide andS-methyl methane thiosulfinate. The blend of volatiles emitted by frass is herbivore-species specific.
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  • 61
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    Antonie van Leeuwenhoek 66 (1994), S. 151-164 
    ISSN: 1572-9699
    Keywords: purple non-sulfur bacteria ; Rhodobacter ; photosynthesis ; CO2 fixation ; anaerobic respiration ; gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Purple non-sulfur phototrophic bacteria, exemplifed byRhodobacter capsulatus andRhodobacter sphaeroides, exhibit a remarkable versatility in their anaerobic metabolism. In these bacteria the photosynthetic apparatus, enzymes involved in CO2 fixation and pathways of anaerobic respiration are all induced upon a reduction in oxygen tension. Recently, there have been significant advances in the understanding of molecular properties of the photosynthetic apparatus and the control of the expression of genes involved in photosynthesis and CO2 fixation. In addition, anaerobic respiratory pathways have been characterised and their interaction with photosynthetic electron transport has been described. This review will survey these advances and will discuss the ways in which photosynthetic electron transport and oxidation-reduction processes are integrated during photoautotrophic and photoheterotrophic growth.
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  • 62
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    Antonie van Leeuwenhoek 65 (1994), S. 311-329 
    ISSN: 1572-9699
    Keywords: photosynthesis ; chlorophyll ; bacteriochlorophyll ; reaction center ; electron transfer ; evolution
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    Topics: Biology
    Notes: Abstract Photosynthetic reaction centers from a variety of organisms have been isolated and characterized. The groups of prokaryotic photosynthetic organisms include the purple bacteria, the filamentous green bacteria, the green sulfur bacteria and the heliobacteria as anoxygenic representatives as well as the cyanobacteria and prochlorophytes as oxygenic representatives. This review focuses on structural and functional comparisons of the various groups of photosynthetic reaction centers and considers possible evolutionary scenarios to explain the diversity of existing photosynthetic organisms.
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  • 63
    ISSN: 1573-5060
    Keywords: maize ; Zea mays ; photoinhibition ; photosynthesis ; low-temperature adaptation ; breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sixty-seven inbred lines of maize were evaluated for resistance to low-temperature photoinhibition of photosynthesis, using a pulse-modulated chlorophyll fluorescence technique. The evaluation procedure was based on leaf discs, which were exposed to a high irradiance (1000 µmol/m2/s) at 7°C. The efficiency of open PSII reaction centres as a reflection of overall photosynthesis was measured before and after a photoinhibition-inducing treatment. Exposure of leaf discs to photoinhibitory condition for 2, 4, and 8 hours resulted in an efficiency reduction of 30, 53 and 83%, respectively. Testing of inbred lines showed large differences for photoinhibition susceptibility. The difference in photosynthetic efficiency between the most extreme lines after a treatment of eight hours was 39%. Resistance to photoinhibition was shown to be relevant under cool field conditions. It proved to be a trait strongly amenable to selection.
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  • 64
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    Photosynthesis research 39 (1994), S. 401-412 
    ISSN: 1573-5079
    Keywords: photosynthesis ; elevated CO2 ; source-sink interactions ; Rubisco
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    Topics: Biology
    Notes: Abstract A range of studies of C3 plants have shown that there is a change in both the carbon flux and the pattern of nitrogen allocation when plants are grown under enhanced CO2. This paper examines evidence that allocation of nitrogen both to and within the photosynthetic system is optimised with respect to the carbon flux. A model is developed which predicts the optimal relative allocation of nitrogen to key enzymes of the photosynthetic system as a function of CO2 concentration. It is shown that evidence from flux control analysis is broadly consistent with this model, although at high nitrogen and under certain conditions at low nitrogen experimental data are not consistent with the model. Acclimation to enhanced CO2 is also assessed in terms of resource allocation between photosynthate sources and sinks. A means of assessing the optimisation of this source-sink allocation is proposed, and several studies are examined within this framework. It is concluded that C3 plants probably possess the genetic feedback mechanisms required to efficiently ‘smooth out” any imbalance within the photosynthetic system caused by a rise in atmospheric CO2.
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  • 65
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    Photosynthesis research 39 (1994), S. 453-462 
    ISSN: 1573-5079
    Keywords: photosynthesis ; Rubisco ; ozone ; oxidative stress ; rbcS mRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ozone induces reductions in net photosynthesis in a large number of plant species. A primary mechanism by which photosynthesis is reduced is through impact on carbon dioxide fixation. Ozone induces loss in Rubisco activity associated with loss in concentration of the protein. Evidence is presented that ozone may induce oxidative modification of Rubisco leading to subsequent proteolysis. In addition, plants exposed to ozone sustain reduction in rbcS, the mRNA for the small subunit of Rubisco. This loss in rbcS mRNA may lead to a reduced potential for synthesis of the protein. The regulation of O3-induced loss of Rubisco, and implications of the decline in this protein in relation to accelerated senescence are discussed.
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    Photosynthesis research 41 (1994), S. 3-5 
    ISSN: 1573-5079
    Keywords: bacteriochlorophylla-protein ; green sulfur bacteria ; Prosthecochloris aestuarii ; Chlorobium limicola ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1961 the green sulfur bacterium-containing mixed culture known as‘Chloropseudomonas ethylicum’ was brought to Brookhaven National Laboratory (USA) from Moscow State University (USSR). The water-soluble bacteriochlorophylla-protein (FMO-protein) was extracted, purified and characterized by absorption and circular dichroism spectroscopy, by X-ray crystallography and by primary structure determination.
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  • 67
    ISSN: 1573-5079
    Keywords: 9-aminoacridine fluorescence ; cyclic electron transport ; Mehler reaction ; photosynthesis ; photosystems ; transthylakoid proton gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The light-dependent quenching of 9-aminoacridine fluorescence was used to monitor the state of the transthylakoid proton gradient in illuminated intact chloroplasts in the presence or absence of external electron acceptors. The absence of appreciable light-dependent fluorescence quenching under anaerobic conditions indicated inhibition of coupled electron transport in the absence of external electron acceptors. Oxygen relieved this inhibition. However, when DCMU inhibited excessive reduction of the plastoquinone pool in the absence of oxygen, coupled cyclic electron transport supported the formation of a transthylakoid proton gradient even under anaerobiosis. This proton gradient collapsed in the presence of oxygen. Under aerobic conditions, and when KCN inhibited ribulose bisphosphate carboxylase and ascorbate peroxidase, fluorescence quenching indicated the formation of a transthylakoid proton gradient which was larger with oxygen in the Mehler reaction as electron acceptor than with methylviologen at similar rates of linear electron transport. Apparently, cyclic electron transport occured simultaneously with linear electron transport, when oxygen was available as electron acceptor, but not when methylviologen accepted electrons from Photosystem I. The ratio of cyclic to linear electron transport could be increased by low concentrations of DCMU. This shows that even under aerobic conditions cyclic electron transport is limited in isolated intact chloroplasts by excessive reduction of electron carriers. In fact, P700 in the reaction center of Photosystem I remained reduced in illuminated isolated chloroplasts under conditions which resulted in extensive oxidation of P700 in leaves. This shows that regulation of Photosystem II activity is less effective in isolated chloroplasts than in leaves. Assuming that a Q-cycle supports a H+/e ratio of 3 during slow linear electron transport, vectorial proton transport coupled to Photosystem I-dependent cyclic electron flow could be calculated. The highest calculated rate of Photosystem I-dependent proton transport, which was not yet light-saturated, was 330 μmol protons (mg chlorophyll h)−1 in intact chloroplasts. If H+/e is not three but two proton transfer is not 330 but 220 μmol (mg Chl H)−1. Differences in the regulation of cyclic electron transport in isolated chloroplasts and in leaves are discussed.
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  • 68
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    Photosynthesis research 40 (1994), S. 35-44 
    ISSN: 1573-5079
    Keywords: allophycocyanin ; chlorophyll a ; linear dichroism ; phycobilisome ; photosynthesis ; state transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Low temperature (77 K) linear dichroism spectroscopy was used to characterize pigment orientation changes accompanying the light state transition in the cyanobacterium, Synechococcus sp. PCC 6301 and those accompanying chromatic acclimation in Porphyridium cruentum in samples stabilized by glutaraldehyde fixation. In light state 2 compared to light state 1 intact cells of Synechococcus showed an increased alignment of allophycocyanin parallel to the cells' long axis whereas the phycobilisomethylakoid membrane fragments exhibited an increased allophycocyanin alignment parallel to the membrane plane. The phycobilisome-thylakoid membrane fragments showed less alignment of a short wave-length chlorophyll a (Chl a) Qy transition dipole parallel to the membrane plane in state 2 relative to state 1. To aid identification of the observed Chl a orientation changes in Synechococcus, linear dichroism spectra were obtained from phycobilisome-thylakoid membrane fragments isolated from red light-grown (increased number of PS II centres) and green light-grown (increased number of PS I centres) cells of the red alga Porphyridium cruentum. An increased contribution of short wavelength Chl a Qy transition dipoles parallel to the long axis of the membrane plane was directly correlated with increased levels of PS II centres in red light-grown P. cruentum. Our results indicate that the transition to state 2 in cyanobacteria is accompanied by an increase in the orientation of allophycocyanin and a decrease in the orientation of Chl a associated with PS II with respect to the thylakoid membrane plane.
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  • 69
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    Photosynthesis research 40 (1994), S. 75-92 
    ISSN: 1573-5079
    Keywords: chilling temperature ; oxygen toxicity ; photoinhibition ; photosynthesis ; photosystems ; superoxide dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When 23 °C-grown potato leaves (Solanum tuberosum L.) were irradiated at 23 °C with a strong white light, photosynthetic electron transport and Photosystem-II (PS II) activity were inhibited in parallel. When the light treatment was given at a low temperature of 3 °C, the photoinhibition of photosynthesis was considerably enhanced, as expected. Surprisingly, no such stimulation of photoinhibition was observed with respect to the PS II function. A detailed functional analysis of the photosynthetic apparatus, using in-vivo fluorescence, absorbance, oxygen and photoacoustic measurements, and artificial electron donors/acceptors, showed a pronounced alteration of PS I activity during light stress at low temperature. More precisely, it was observed that both the pool of photooxidizeable reaction center pigment (P700) of PS I and the efficiency of PS I to oxidize P700 were dramatically reduced. Loss of P700 activity was shown to be essentially dependent on atmospheric O2 and to require a continued flow of electrons from PS II, suggesting the involvement of the superoxide anion radical which is produced by the interaction of O2 and the photosynthetic electron-transfer chain through the Mehler reaction. Mass spectrometric measurements of O2 exchange by potato leaves under strong illumination did not reveal, however, any stimulation of the Mehler reaction at low temperature, thus leading to the conclusion that O2 toxicity mainly resulted from a chilling-induced inhibition of the scavenging system for O2-radicals. Support for this interpretation was provided by the light response of potato leaves infiltrated with an inhibitor (diethyldithiocarbamate) of the chloroplastic Cu-Zn superoxide dismutase. It was indeed possible to simulate the differential inhibition of the PS II photochemical activity and the linear electron transport observed during light stress at low temperature by illuminating at 23 °C diethyldithiocarbamate-poisoned leaves. The experimental data presented here suggests that (i) the previously reported resistance of PS I to photoinhibition damage in-vivo is not an intrinsic property of PS I but results from efficient protective systems against O2 toxicity, (ii) PS I is photoinhibited in chilled potato leaf due to the inactivation of this PS I defence system and (iii) PS I is more sensitive to superoxide anion radicals than PS II.
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    Photosynthesis research 40 (1994), S. 207-221 
    ISSN: 1573-5079
    Keywords: photosynthesis ; unicellular algae ; ion effects ; manganese ; blue light ; synchronized growth ; algal mass cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This personal perspective records research experiences in chemistry and biology at four German universities, two before and two after World War II. The research themes came from cytophysiology of green unicellular algae, in particular their photosynthesis. The function of inorganic ions in photosynthesis and dark respiration was investigated at different degrees of specific mineral stress (deficiencies), and the kinetics of recovery followed after the addition of the missing element. Two types of recovery of photosynthesis were observed: indirect restitution via growth processes and immediate normalisation. From the latter case (K+, phosphate, Mn++) the effect of manganese was emphasized as its role in photosynthetic O2 evolution became established during our research. Other themes of our group, with some bearing on photosynthesis were: synchronization of cell growth by light-dark change and effects of blue (vs. red) light on the composition of green cells. Some experiences in connection with algal mass cultures are included. Discussion of several editorial projects shows how photosynthesis, as an orginally separated field of plant biochemistry and biophysics, became included into general cell physiology and even ecophysiology of green plants. The paper contains an appreciation of the authors' main mentor Kurt Noack (1888–1963) and of Ernst Georg Pringsheim (1881–1970), founder of experimental phycology.
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  • 71
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    Photosynthesis research 41 (1994), S. 27-28 
    ISSN: 1573-5079
    Keywords: photosynthesis ; reaction center ; green bacteria ; heliobacteria ; gene ; chlorosome ; cytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recommendations are given for naming of genes coding for reaction center, antenna and electron transport proteins in green photosynthetic bacteria and heliobacteria
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  • 72
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    Keywords: photosynthesis ; Chlorobium tepidum ; antenna ; bacteriochlorophylla protein ; energy transfer ; chlorosome ; green bacteria
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    Topics: Biology
    Notes: Abstract The BChla-containing Fenna-Matthews-Olson (FMO) protein from the green sulfur bacteriumChlorobium tepidum was purified and characterized. Fluorescence spectra indicate that efficient excited state quenching occurs at neutral or oxidizing redox potentials. The major fluorescence lifetime at room temperature is approximately 60 ps in samples that are in neutral or oxidizing conditions, and approximately 2 ns in samples where the strong reductant sodium dithionite has been added. A similar change is observed in pump-probe picosecond absorbance difference experiments, where the long life time component increases after dithionite addition. A 16 Gauss wide EPR signal with g factor =2.005 is observed in samples without dithionite. This signal largely disappears upon addition of dithionite. Dithionite induces large reversibile changes in the 77 K absorbance spectra of the purified FMO protein and in whole cells. These results indicate that the FMO protein contains redox active groups, which may be involved in the regulation of energy transfer. Room temperature circular dichroism and low temperature absorption spectra show that dithionite also induces conformational or structural changes of the FMO protein complex.
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  • 73
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    Plant and soil 164 (1994), S. 97-105 
    ISSN: 1573-5036
    Keywords: alcohol dehydrogenase ; drought ; flooding ; photosynthesis ; tropical grasses ; water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Long dry seasons or permanent flooding, typical of tropical savannas, severely limit the growth of pasture plants. This study compares the responses of water relations, carbon assimilation and alcohol dehydrogenase (ADH) activity to drought and flooding in four perennial C4 grasses: the tufted or caespitose Hyparrhenia rufa and Andropogon gayanus (CIAT 621) and the stoloniferous Brachiaria mutica and Echinochloa polystachya. Plants of the four species were subjected to medium term flooding (20–25 days) and moderate drought in a greenhouse. Leaf water potential (Ψ), stomatal conductance (Gs) and photosynthesis rate (Pn) were measured throughout the experiment and ADH activity was measured in flooded and control plants. Moderate drought produced similar effects in all grasses reducing Gs which caused reduced Pn. Net photosynthesis compensation point was reached at the lowest Ψ in A. gayanus which was considered as the most drought tolerant. The responses to flooding varied across species. Andropogon gayanus and H. rufa showed early stomatal closure without concurrent decrease in Ψ and leaf turgor. This low Gs was responsible of reduced Pn and growth rate. There was a slight increase of Gs in the middle of the flooding period and both grasses recovered pre-stress Gs and Pn after drainage. ADH activity increased markedly only in A. gayanus under flooding suggesting that this grass was the most flood-sensitive. Stomatal aperture, Pn and ADH activity in B. mutica and E. polystachya were not affected by flooding. The higher flood-tolerance in these grasses might be attributed to enhanced oxygen diffusion to the roots through the hollow stolons, development of advantitious rootlets and large aerenchyma in the roots which compensate for the reduction of soil oxygen and permit the maintenance of root activity.
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  • 74
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    Euphytica 76 (1994), S. 235-238 
    ISSN: 1573-5060
    Keywords: Triticum aestivum ; wheat ; photosynthesis ; gene action ; heritability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Gene action and heritability for photosynthetic activity were estimated from generation means in two wheat crosses during two stages (5 th leaf and flag leaf between 2 and 5 days after anthesis). Six generations were available for each cross: parents (P1 and P2), F1, F2 and backcrosses (BC1 and BC2). Correlations between some morphophysiological characters and photosynthetic activity of the flag leaf was also determined. The joint scaling test described by Mather & Jinks was used to determine the gene action. It showed that them; [d]; [h]; [i], [l] (mean, additivity, dominance, additive x additive interallelic interaction effects, dominance x dominance interallelic interaction effects) model fits the two crosses at both measurement times. All the model genetic components were significant for the flag leaf, however for the 5 th leaf only [h]; [i] and [l] were significant. The presence of additive and additive x additive effects suggested the possibility of selecting for this character using the flag leaf so as to obtain pure inbred lines. Dominance effects [h] were negative and dominance x dominance effects [l] were positive. Broad sense heritability values were medium to low. There were no correlations between the studied morphophysiological characters and the photosynthetic activity.
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  • 75
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    Photosynthesis research 39 (1994), S. 191-199 
    ISSN: 1573-5079
    Keywords: photoinhibition ; photosynthesis ; protein degradation ; singlet oxygen ; TEMP (2,2,6,6-tetramethylpiperidine) ; thylakoid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exposure of isolated spinach thylakoids to high intensity illumination (photoinhibition) results in the well-characterized impairment of Photosystem II electron transport, followed by degradation of the D1 reaction centre protein. In the present study we demonstrate that this process is accompanied by singlet oxygen production. Singlet oxygen was detected by EPR spectroscopy, following the formation of stable nitroxide radicals from the trapping of singlet oxygen with a sterically hindered amine TEMP (2,2,6,6-tetramethylpiperidine). There was no detectable singlet oxygen production during anaerob photoinhibition or in the presence of sodium-azide. Comparing the kinetics of the loss of PS II function and D1 protein with that of singlet oxygen trapping suggests that singlet oxygen itself or its radical product initiates the degradation of D1.
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  • 76
    ISSN: 1573-5079
    Keywords: cyanobacteria ; excitation energy ; herbicide ; photochemical apparatus ; photosynthesis ; pyridazinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract SANDOZ 9785, also known as BASF 13.338, is a pyridazinone derivative that inhibits Photosystem II (PS II) activity leading to an imbalance in the rate of electron transport through the photosystems. Synechococcus sp. strain PCC 7942 cells grown in the presence of sublethal concentration of SANDOZ 9785 (SAN 9785) for 48 hours exhibited a 20% decrease in Chl a per cell. However, no changes were observed in the content of phycocyanin per cell, the size of the phycobilisomes or in the PS II:PS I ratio. From an estimate of PS II electron transport rate under varying light intensities and spectral qualities and analysis of room temperature Chl a fluorescence induction, it was deduced that growth of Synechococcus PCC 7942 in the presence of SAN 9785 leads to a redistribution of excitation energy in favour of PS II. Though the redistribution appears to be primarily caused by changes affecting the Chl a antenna of PS II, the extent of energetic coupling between phycobilisomes and PS II is also enhanced in SAN 9785 grown Synechococcus PCC 7942 cells. There was a reduction in the effective size of PS I antenna based on measurement of P700 photooxidation kinetics. These results indicate that when PS II is partially inhibited, the structure of photosynthetic apparatus alters to redistribute the excitation energy in favour of PS II so that the efficiency of utilization of light energy by the two photosystems is optimized. Our results suggest that under the conditions used, drastic structural changes are not essential for redistribution of excitation energy between the photosystems.
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  • 77
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    Photosynthesis research 39 (1994), S. 351-368 
    ISSN: 1573-5079
    Keywords: CO2 enrichment ; gas exchange ; greenhouse effect ; photosynthesis ; responses to CO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nature of photosynthetic acclimation to elevated CO2 is evaluated from the results of over 40 studies focusing on the effect of long-term CO2 enrichment on the short-term response of photosynthesis to intercellular CO2 (the A/Ci response). The effect of CO2 enrichment on the A/Ci response was dependent on growth conditions, with plants grown in small pots (〈 5 L) or low nutrients usually exhibiting a reduction of A at a given Ci, while plants grown without nutrient deficiency in large pots or in the field tended to exhibit either little reduction or an enhancement of A at a given Ci following a doubling or tripling of atmospheric CO2 during growth. Using theoretical interpretations of A/Ci curves to assess acclimation, it was found that when pot size or nutrient deficiency was not a factor, changes in the shape of A/Ci curves which are indicative of a reallocation of resources within the photosynthetic apparatus typically were not observed. Long-term CO2 enrichment usually had little effect or increased the value of A at all Ci. However, a minority of species grown at elevated CO2 exhibited gas exchange responses indicative of a reduced amount of Rubisco and an enhanced capacity to metabolize photosynthetic products. This type of response was considered beneficial because it enhanced both photosynthetic capacity at high CO2 and reduced resource investment in excessive Rubisco capacity. The ratio of intercellular to ambient CO2 (the Ci/Ca ratio) was used to evaluate stomatal acclimation. Except under water and humidity stress, Ci/Ca exhibited no consistent change in a variety of C3 species, indicating no stomatal acclimation. Under drought or humidity stress, Ci/Ca declined in high-CO2 grown plants, indicating stomata will become more conservative during stress episodes in future high CO2 environments.
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    Photosynthesis research 39 (1994), S. 463-473 
    ISSN: 1573-5079
    Keywords: global climate change ; ozone depletion ; photosynthesis ; Photosystem II ; productivity ; UV-B radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic apparatus of some plant species appears to be well-protected from direct damage from UV-B radiation. Leaf optical properties of these species apparently minimizes exposure of sensitive targets to UV-B radiation. However, damage by UV-B radiation to Photosystem II and Rubisco has also been reported. Secondary effects of this damage may include reductions in photosynthetic capacity, RuBP regeneration and quantum yield. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity in many plant species. In addition to variability in sensitivity to UV-B radiation, the effects of UV-B radiation are further confounded by other environmental factors such as CO2, temperature, light and water or nutrient availability. Therefore, we need a better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction between UV-B and other environmental factors in order to adequately assess the probable consequences of a change in solar radiation.
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    Photosynthesis research 40 (1994), S. 107-117 
    ISSN: 1573-5079
    Keywords: photosynthesis ; state adaptations ; shade adaptation ; cyanobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A profile of high light to intense self-shading conditions was constructed using a white light source and cultures of the cyanobacterium Synechococcus 6301; this profile approximates to a natural self-shading gradient of decreasing light intensity and PS II/PS I excitation ratio. Samples of S.6301 were placed along this profile and allowed to state adapt. To separate the effects of light intensity and wavelength on state adaptation, samples were also placed in a shade profile produced by a white light source and neutral density filters. After adaptation, samples were fixed in their resulting state by the addition of glutaraldehyde, and fluorescence measurements were made at 35° C or –160 °C. It is concluded: 1. Under conditions of deep shade (〈5 μmol m−2s−1 PAR) and weak shade (〉200 μmol m−2s−1 PAR), cells adapt to a low PS II fluorescence state (state 2); in moderate shade (20–60 μmol m−2s−1PAR) cells adapt to a high PS II fluorescence state (state 1). We suggest these findings provide evidence for the operation of different factors on the control of state adaptations in cyanobacteria; one set operates at low light and another at high light intensities. 2. Under conditions of self-shading, there is little evidence to support the contention that state adaptations in cyanobacteria are produced by wavelength-dependent changes in the PS II/PS I excitation ratio, instead, it appaers they are produced by changes in the intensity of incident irradiation. 3. The observed fluorescence changes do not appear to involve major changes in the phycobilisome sensitisation of PS II and PS I. Instead, it appears that these changes are effected by alterations in ΦF of PS II (i.e. changes in PS II excitation density caused by alterations in the rate constants controlling spillover to PS I, photochemistry, fluorescence emission or thermal deactivation.
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    Photosynthesis research 41 (1994), S. 75-88 
    ISSN: 1573-5079
    Keywords: photosynthesis ; carbon assimilation ; photosynthetic bacteria ; citric-acid cycle ; pyruvate synthase ; fermentation ; heliobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Heliobacteria are a group of anoxygenic phototrophs that can grow photoheterotrophically in defined minimal media on only a limited range of organic substrates as carbon sources. In this study the mechanisms which operate to assimilate carbon and the routes employed for the biosynthesis of cellular intermediates were investigated in a newHeliobacterium strain, HY-3. This was achieved using two approaches (1) by measuring the activities of key enzymes in cell-free extracts and (2) by the use of13C nuclear magnetic resonance (NMR) spectroscopy to analyze in detail the labelling pattern of amino-acids of cells grown on [13C] pyruvate and [13C] acetate.Heliobacterium strain HY-3 was unable to grow autotrophically on CO2/H2 and neither (ATP)-citrate lyase nor ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPcase) were detectable in cell-free extracts. The enzyme profile of pyruvate grown cells indicated the presence of a pyruvate:acceptor oxidoreductase at high specific activity which could convert pyruvate to acetyl-Coenzyme A. No pyridine nucleotide dependent pyruvate dehydrogenase complex activity was detected. Of the citric-acid cycle enzymes, malate dehydrogenase, fumarase, fumarate reductase and an NADP-specific isocitrate dehydrogenase were readily detectable but no aconitase or citrate synthase activity was found. However, the labelling pattern of glutamate in long-term 2-[13C] acetate incorporation experiments indicated that a mechanism exists for the conversion of carbon from acetyl-CoA into 2-oxoglutarate. A 2-oxoglutarate:acceptor oxidoreductase activity was present which was also assayable by isotope exchange, but no 2-oxoglutarate dehydrogenase complex activity could be detected. Heliobacteria appear to use a type of incomplete reductive carboxylic acid pathway for the conversion of pyruvate to 2-oxoglutarate but are unable to grow autotrophically using this metabolic route due to the absence of ATP-citrate lyase.
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  • 81
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    Keywords: photosynthesis ; bacteriochlorophyll ; electron acceptor ; iron-sulfur center ; Photosystem I ; heliobacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Treatment of membranes ofHeliobacillus mobilis with high concentrations of the chaotropic agent urea resulted in the removal of the iron-sulfur centers FA and FB from the reaction center, as indicated by EPR spectra under strongly reducing conditions. In urea-treated membranes, transient absorption measurements upon a laser flash indicated a recombination between the photo-oxidized primary donor P798+ and a reduced acceptor with a time constant of 20 ms at room temperature. Benzylviologen, vitamin K-3 and methylene blue were found to accept electrons from the reduced acceptor efficiently. A differential extinction coefficient of 225–240 mM−1 cm−1 at 798 nm was determined from experiments in the presence of methylene blue. Transient absorption difference spectra between 400 and 500 nm in the presence and absence of artificial acceptors indicated that the electron acceptor involved in the 20 ms recombination has an absorption spectrum similar to that of an iron-sulfur center. This iron-sulfur center was assigned to be analogous to FX of Photosystem I. Our results provide evidence in support of the presence of FX in heliobacteria, which was proposed on the basis of the reaction center polypeptide sequence (Liebl et al. (1993) Proc. Natl. Acad. Sci. USA 90: 7124–7128). Implications for the electron transfer pathway in the reaction center of heliobacteria are discussed.
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  • 82
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    Keywords: energy transfer ; green bacteria ; photosynthesis ; picosecond spectroscopy ; pigment system ; (Chloroflexus aurantiacus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Examination was made of changes in fluorescence polarization plane by energy transfer in the chlorosomes of the green photosynthetic bacterium,Chloroflexus aurantiacus. Fluorescence anisotropy in the picosecond (ps) time region was analyzed using chlorosomes suspended in solution as well as those oriented in a polyacrylamide gel. When the main component of BChlc was preferentially excited, the decay of fluorescence anisotropy was found to depend on wavelength. In the chlorosome suspension, the anisotropy ratio of BChlc changed from 0.31 to 0.24 within 100 ps following excitation. In the baseplate BChla region, this ratio decreased to a negative value (−0.09) from the initial 0.14. In oriented samples, the degree of polarization remained at 0.68 for BChlc, and changed from 0.25 to −0.40 for the baseplate BChla by excitation light whose electric vector was parallel to the longest axis of chlorosomes. In the latter case, there was a shift from 0.30 to −0.55 by excitation perpendicular to the longest axis. Time-resolved fluorescence polarization spectra clearly indicated extensive changes in polarization plane accompanied by energy transfer. The directions of polarization plane of emission from oriented samples were mostly dependent on chlorosome orientation in the gel but not on that of the polarization plane of excitation light. Orientations of the dipole moment of fluorescence components was consistent with that of absorption components as determined by the linear dichroism (Matsuura et al. (1993) Photochem. Photobiol. 57: 92–97). A model for molecular organization of BChlc anda in chlorosomes is proposed based on anisotropic optical properties.
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    Photosynthesis research 41 (1994), S. 285-294 
    ISSN: 1573-5079
    Keywords: heliobacteria ; reaction center ; photosynthesis ; 16S rRNA sequence ; cyanobacteria ; Gram-positive bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolutionary position of the heliobacteria, a group of green photosynthetic bacteria with a photosynthetic apparatus functionally resembling Photosystem I of plants and cyanobacteria, has been investigated with respect to the evolutionary relationship to Gram-positive bacteria and cyanobacteria. On the basis of 16S rRNA sequence analysis, the heliobacteria appear to be most closely related to Gram-positive bacteria, but also an evolutionary link to cyanobacteria is evident. Interestingly, a 46-residue domain including the putative sixth membrane-spanning region of the heliobacterial reaction center protein shows rather strong similarity (33% identity and 72% similarity) to a region including the sixth membrane-spanning region of the CP47 protein, a chlorophyll-binding core antenna polypeptide of Photosystem II. The N-terminal half of the heliobacterial reaction center polypeptide shows a moderate sequence similarity (22% identity over 232 residues) with the CP47 protein, which is significantly more than the similarity with the Photosystem I core polypeptides in this region. An evolutionary model for photosynthetic reaction center complexes is discussed, in which an ancestral homodimeric reaction center protein (possibly resembling the heliobacterial reaction center protein) with 11 membrane-spanning regions per polypeptide has diverged to give rise to core of Photosystem I, Photosystem II, and of the photosynthetic apparatus in green, purple, and heliobacteria.
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  • 84
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    Keywords: photosynthesis ; Photosystem II ; superoxide radical ; superoxide dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the present study the light induced formation of superoxide and intrinsic superoxide dismutase (SOD) activity in PS II membrane fragments and D1/D2/Cytb559-complexes from spinach have been analyzed by the use of ferricytochrome c (cyt c(III)) reduction and xanthine/xanthine oxidase as assay systems. The following results were obtained: 1.) Photoreduction of Cyt c (III) by PS II membrane fragments is induced by addition of sodium azide, tetracyane ethylene (TCNE) or carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (FCCP) and after removal of the extrinsic polypeptides by a 1M CaCl2-treatment. This activity which is absent in control samples becomes completely inhibited by the addition of exogenous SOD. 2.) The TCNE induced cyt c(III) photoreduction by PS II membrane fragments was found to be characterized by a half maximal concentration of c1/2=10 μM TCNE. Simultaneously, TCNE inhibits the oxygen evolution rate of PS II membrane fragments with c1/2≈ 3 μM. 3.) The photoproduction of O2 − is coupled with H+-uptake. This effect is diminished by the addition of the O2 −-trap cyt c(III). 4.) D1/D2/Cytb559-complexes and PS II membrane fragments deprived of the extrinsic proteins and manganese exhibit no SOD-activity but are capable of producing O2 − in the light if a PS II electron donor is added. Based on these results the site(s) of light induced superoxide formation in PS II is (are) inferred to be located at the acceptor side. A part of the PS II donor side and Cyt b559 in its HP-form are proposed to provide an intrinsic superoxide dismutase (SOD) activity.
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  • 85
    ISSN: 1573-5079
    Keywords: photosynthesis ; chlorophyll fluorescence ; high energy-state quenching ; calcium release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have measured thermoluminescence (TL) and chlorophyll fluorescence from leaves of peas grown under an intermittent light regime (IML) and followed changes in those leaves during greening. IML peas show low variable fluorescence and a certain capacity for reversible non-photochemical quenching. It has been suggested that reversible quenching may be caused by pH-dependent release of Ca2+ from Photosystem II (PS II) (Krieger and Weis (1992) Photosynthetica 27: 89–98). Under conditions in which reversible non-photochemical quenching occurs, a TL band at around 50 °C is observed, in the presence of DCMU, in IML leaves. A band in this temperature range has previously been observed in PS II depleted of Ca2+ (Ono and Inoue (1989) Biochimica et Biophysica Acta 973: 443–449). The 50 °C band disappears upon dark adaptation. In mature leaves, no significant band is seen at 50 °C. It is concluded that, in IML leaves, reversible quenching may be related to the release of Ca2+ from Photosystem II. However, it seems that in the mature system, under most conditions, such release does not contribute significantly to quenching
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  • 86
    ISSN: 1573-5079
    Keywords: electron transport rate ; mesophyll conductance to CO2 diffusion ; photosynthesis ; photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic electron transport drives the carbon reduction cycle, the carbon oxidation cycle, and any alternative electron sinks such as nitrogen reduction. A chlorophyll fluorescence— based method allows estimation of the total electron transport rate while a gas-exchange-based method can provide estimates of the electron transport needed for the carbon reduction cycle and, if the CO2 partial pressure inside the chloroplast is accurately known, for the carbon oxidation cycle. The gas-exchange method cannot provide estimates of alternative electron sinks. Photosynthetic electron transport in flag leaves of wheat was estimated by the fluorescence method and gasexchange method to determine the possible magnitude of alternative electron sinks. Under non-photorespiratory conditions the two measures of electron transport were the same, ruling out substantial alternative electron sinks. Under photorespiratory conditions the fluorescence-based electron transport rate could be accounted for by the carbon reduction and carbon oxidation cycle only if we assumed the CO2 partial pressure inside the chloroplasts to be lower than that in the intercellular spaces of the leaves. To further test for the presence of alternative electron sinks, carbon metabolism was inhibited by feeding glyceraldehyde. As carbon metabolism was inhibited, the electron transport was inhibited to the same degree. A small residual rate of electron transport was measured when carbon metabolism was completely inhibited which we take to be the maximum capacity of alternative electron sinks. Since the alternative sinks were small enough to ignore, the comparison of fluorescence and gas-exchange based methods for measuring the rate of electron transport could be used to estimate the mesophyll conductance to CO2 diffusion. The mesophyll conductance estimated this way fell as wheat flag leaves senesced. The age-related decline in photosynthesis may be attributed in part to the reduction of mesophyll conductance to CO2 diffusion and in part to the estimated decline of ribulose 1,5-bisphosphate carboxylase amount.
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  • 87
    ISSN: 1573-5079
    Keywords: photosynthesis ; leaf age ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the photosynthetic light-response curve during leaf development were determined for the fourth leaf of maize crops sown on 23 April and 10 June. Temperatures were unusually mild during late spring/early summer and neither crop experienced chilling damage. The concept of thermal time was used to take into account the effects of different temperature regimes on developmental stage, thereby enabling photosynthetic light-response data to be combined for both crops to describe the general response. Large variations in the upper asymptote (Asat) and convexity (Θ) of the light-response curve occurred during leaf development, but the maximum quantum yield of CO2 assimilation remained relatively constant throughout. Dark respiration rates showed a small but significant decrease with leaf age and generally ranged between 5 and 10% of Asat. A simple mathematical model was developed to assess the sensitivity of daily leaf photosynthesis (AL) to reductions in the Asat, Θ and the initial slope (Φ) of the light-response curve at different stages of leaf development. On bright sunny days, and at all developmental stages, AL was ca. twice as sensitive to reductions in Asat than to reductions in Φ and Θ. In overcast conditions, however, all three parameters contributed significantly to reductions in leaf photosynthesis, although the contribution of Φ was greatest during early leaf growth, while older leaves were most sensitive to depressions in Asat. The implications of these results for modelling the sensitivity of canopy photosynthesis to chill-induced photoinhibition of the light-response curve are discussed.
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  • 88
    ISSN: 1573-1561
    Keywords: Floral oils ; cacao ; Theobroma cacao ; Sterculiaceae ; attraction ; Diptera ; Ceratopogonidae ; Cecidomyiidae ; Hymenoptera ; Apidae ; pollination ; 1-pentadecene ; n-pentadecene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Steam-distilled floral fragrance oils from nine distinctive cultivars ofTheobroma cacao L. (Sterculiaceae) in Costa Rica were examined with GC-MS to determine whether or not major differences existed among these cultivars for volatile constituents comprising 50% or more of the samples. The cultivars selected for floral oil analyses were chosen to represent diverse cultivars having supposedly different genetic backgrounds and histories of artificial selection for agronomic purposes. Cluster analysis revealed two major groupings of cultivars: those with higher molecular weight dominant compounds, and those having lower molecular weight compounds. Additionally, one cultivar, Rim-100, selected from criollo or ancestral-type cacao in Mexico and resembling criollo in the appearance of flowers and fruits, formed an extreme group having the highest molecular weight profile for major volatile compounds. Based upon these analyses, bioassays using McPhail traps were performed in an abandoned cacao plantation in northeastern Costa Rica during rainy and dry seasons to determine the relative attraction of these oils to flying insects. Bioassays revealed that the Rim-100 cultivar attracted by far the greatest numbers of cacao-associated midges (Diptera: Ceratopogonidae and Cecidomyiidae), as well as stingless bees (Hymenoptera: Apidae: Meliponinae), suggesting that a floral fragrance having high-molecular-weight volatiles is more potent as an attractant to flying insects than floral oils having lower-molecular-weight compounds. It is suggested that Rim-100 more closely resembles an ancestral or wild-type cacao than the other cultivars examined, and therefore it is more effective in attracting opportunistic dipteran floral visitors and pollinators than other cultivars in plantation settings. Several of the major volatile compounds found in the floral oils ofT. cacao and other species ofTheobroma occur in mandibular and other exocrine glands in various bees, including stingless bees and halictids, known visitors ofTheobroma flowers. These compounds are particularly present in noncultivated species ofTheobroma and have much more noticeable fragrances than the seemingly scentless flowers of cultivatedT. cacao selected for agriculture. It is hypothesized that the floral attraction system of ancestral or wild (noncultivated)T. cacao and other species ofTheobroma may have evolved to attract certain bees as their principal pollinators in natural habitats in the Neotropics, with a floral reward hypothesized as being sociochemicals needed by bees for mating, foraging, territorial defense, etc. Because of the many generations of extensive selection by cloning for desired cultivars,T. cacao might have lost much of its original floral attraction system for bees, instead being pollinated opportunistically by dipterans in plantation habitats. This may help to explain why natural pollination in cultivatedT. cacao is generally very poor relative to observed levels of fruit-set in wild or noncultivated species ofTheobroma.
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  • 89
    ISSN: 1573-1561
    Keywords: Honey bee ; Apis mellifera ; Hymenoptera ; Apidae ; gas chromatography ; electroantennogram ; conditioned proboscis extension ; olfactory discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A novel technique for the simultaneous monitoring of electroan-tennogram (EAG) and conditioned proboscis extension (CPE) responses of honey bees to the effluent from a gas chromatograph (GC) was developed to locate biologically active components in blends of plant volatiles and to investigate odor recognition at the peripheral and behavioral levels. A six-component mixture, comprising compounds previously identified as oilseed rape floral volatiles, was used as the stimulus. Standard CPE and EAG recordings were done as a reference. EAG responses were elicited from unconditioned bees by all the components presented either in the coupled or the standard mode. Conditioned bees gave larger EAG responses than unconditioned bees, suggesting that antennal sensitivity is enhanced by conditioning. At the behavioral level, in both the standard and the coupled modes, only conditioned bees showed the proboscis extension response, with the majority of individuals responding to linalool, 2-phenylethanol, and benzyl alcohol.
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  • 90
    ISSN: 1573-1561
    Keywords: Veratrum album ; ceveratrum alkaloids ; plant-insect interactions ; sequestration ; hemolymph ; feeding deterrence ; Rhadinoceraea nodicornis ; Aglaostigma sp. ; Hymenoptera ; Tenthredinidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The larvae of the specialist sawflyRhadinoceraea nodicornis Konow (Hymenoptera, Tenthredinidae) store in their hemolymph ceveratrum alkaloids originating from the host plantVeratrum album L. (Liliales, Melanthiaceae). The major alkaloid found in the hemolymph is 3-acetyl-zygadenine. Qualitative and quantitative data showed that the plant alkaloid 3-angeloylzygadenine is most probably metabolized in the larval gut to zygadenine and then acetylated. A still unidentified alkaloid with a molecular weight of 591 Da was detected in plant leaves as well as in the gut, hemolymph, and excrement of larvae. Protoveratrine A and B, on the other hand, seem to be degraded by the larvae. These findings indicate that the pathway of ceveratrum alkaloids inR. nodicornis larvae is fourfold: direct sequestration, metabolism followed by sequestration, excretion of intact alkaloids, and degradation. In contrast, no ceveratrum alkaloids were detected in the hemolymph and excrement of larvae of the generalist sawflyAglaostigma sp. fed withV. album leaves. Bioassays with the antMyrmica rubra L. proved that the hemolymph ofR. nodicornis larvae is highly deterrent and toxic. In bioassays evaluating defensive efficiency against predators (ants, spiders, and bushcrickets), no larvae were eaten. Ceveratrum alkaloids were also detected in the hibernating prepupae ofR. nodicornis. In feeding bioassays, the shrewCrocidura russula Hermann rarely fed upon prepupae, suggesting that this stage is also protected from predation to some degree. In field surveys, the only parasitoids recorded were two ichneumonid species that are believed to be specialized onR. nodicornis. Bioassays and field observations enable us to suppose thatR. nodicornis and its enemies produce a food web of ion connectance.
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  • 91
    ISSN: 1570-7458
    Keywords: Vitis vinifera ; Empoasca vitis ; leafhopper ; photosynthesis ; transpiration ; stomatal conductance ; mesophyll conductance ; growth ; yield ; fruit quality ; starch ; carbohydrate reserves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of the grape leafhopper,Empoasca vitis, on leaf gas exchange, plant growth, yield, fruit quality and carbohydrate reserves of the grapevines,Vitis vinifera L., was studied. Gas exchange was measured on the discolored (red) and the green parts of infested main leaves and on leaves from uninfested vines. Photosynthesis and mesophyll conductance were severely reduced on main leaves showing leafhopper feeding symptoms. The stomatal conductance of the red leaf section of infested main leaves was lower than on undamaged control leaves. Additionally, the red leaf section of infested main leaves showed lower transpiration rates when compared to the green parts of the same leaves and to undamaged control leaves. Gas exchange processes of lateral leaves were not affected by leafhopper feeding. Leafhopperload on main leaves was correlated to visual damage symptoms. At 71.8 leafhopper-days per leaf up to 40% of the main leaf area of the infested plants was discolored from the borders towards the center. Lateral leaves showed no feeding symptoms. Shoot diameter, pruning weight and carbohydrate reserves in the wood were not affected by leafhoppers. Lateral leaf area growth was significantly stimulated on plants infested by leafhoppers. No decrease in yield and fruit quality with leafhopper-loads up to 71.8 leafhopper-days per leaf were observed.
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  • 92
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    Entomologia experimentalis et applicata 69 (1993), S. 33-39 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; Aphidiinae ; aphid ; sex pheromone ; parasitoid ; Praon volucre ; Aphidius rhopalosiphi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Laboratory and field experiments provided evidence for the release of sex pheromones by virgin femalePraon volucre Haliday andAphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Braconidae, Aphidiinae). In Petri dish biosassays, rubber or vermiculite models treated with crude virgin female extracts were frequently approached by males and elicited rapid wing-fanning behaviour and copulation attempts. Delta-shaped water traps containing live virgin females caught large numbers of conspecific males when placed in winter wheat crops. Trapping slightly below crop height resulted in higher catches than trapping above the crop canopy.
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  • 93
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    Entomologia experimentalis et applicata 68 (1993), S. 1-7 
    ISSN: 1570-7458
    Keywords: Hybridoma ; detectability period ; venom ; predation ; serology ; protease ; Vespidae ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to derive quantitative estimates of predation rate from serological gut analysis data, one must have an estimate of the interval during which a meal can be detected after feeding. In practice this has turned out to be ‘Dmax,’ defined as ‘...the time from finishing a meal until that meal could just no longer be detected in any individuals.’ However Dmax substitutes an absolute limit for what is really a continuous variable with significant variation. We examined this problem in a study of the detectability ofHelicoverpa zea Boddie (Lepidoptera: Noctuidae) fifth instar remains in the guts ofPolistes metricus Say (Hymenoptera: Vespidae). Wasps were maintained onTrichoplusia ni (Hübner) (Lepidoptera: Noctuidae) fifth instars before being fed a singleH. zea fifth instar. They were killed and frozen at 0, 24, 48 and 96 h intervals, with those held for more than 24 h fed a singleT. ni fifth instar at 24 h intervals in order to simulate continued feeding. Wasp abdomens were assayed by immunodot, using a monoclonal antibody toH. zea arylphorin. There was a logarithmic decay in the proportion ofP. metricus positive over time, a singleH. zea fifth instar meal having a detectability half-life of 19.4 h at field temperatures. If prey antigen detectability decays exponentially, then a detectability half-life is a more appropriate unit of detectability than an absolute detectability period.
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  • 94
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    Entomologia experimentalis et applicata 68 (1993), S. 219-229 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; Aphidiidae ; Homoptera ; Aphididae ; Schizaphis graminum ; wheat ; tritrophic interactions ; learning ; host-habitat location
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of experience on the responsiveness of the aphidiid parasitoidLysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) to host-associated cues was investigated using a wind-tunnel bioassay. Naive females were able to discriminate between uninfested wheat (Triticum aestivum L.) and wheat infested withSchizaphis gramimum (Rondani) (Homoptera: Aphididae), but oviposition experience significantly increased the parasitoid's propensity to respond to aphid-infested plants with upwind, targeted flight. The behavioural change associated with such experience was acquired rapidly (within five minutes) and persisted for at least 24 h. The parasitoid could be successfully conditioned to associate a novel odour with the presence of hosts, suggesting that the increase in response to aphid-infested plants which occurs as a result of experience is probably due to associative learning of olfactory cues from the plant-aphid complex.
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  • 95
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    Entomologia experimentalis et applicata 67 (1993), S. 183-192 
    ISSN: 1570-7458
    Keywords: symbionts ; thelytoky ; arrhenotoky ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microbe-associated parthenogenesis (thelytoky) has been discovered in nineTrichogramma species, parasitoids of mainly lepidopteran eggs. Parthenogenetic and bisexual conspecifics co-occur in many field populations. As an initial step to understand the dynamics of these two reproductive strategies we studied the effect of microbe-associated parthenogenesis on fecundity. The fecundity of two parthenogenetic isofemale lines ofT. pretiosum and one ofT. deion was compared with bisexual lines derived from them by antibiotic treatment. In all three cases parthenogenetic females were less fecund over their lifetime than bisexual females. Also, parthenogenetic females produced fewer daughters in two cases and in one case a similar number of daughters as their respective bisexual counterparts. The lack of mating and insemination was excluded as an explanation for the reduced fecundity of parthenogenetic females, because mated and virgin parthenogenetic females produce the same number of offspring. Antibiotic treatment can also be excluded because females of field-collected bisexual line treated with antibiotics produced the same number of offspring as untreated females. The reduced fecundity of parthenogenetic females was caused by a lower number of eggs being laid rather than by a greater developmental mortality. Parthenogenetic females produced less daughters than bisexual females when host availability was not limiting, but when host availability was severely limited, parthenogenetic females produced more daughters than the bisexual females.
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  • 96
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    Entomologia experimentalis et applicata 67 (1993), S. 233-239 
    ISSN: 1570-7458
    Keywords: inbreeding ; colonization ; isofemale line ; Drosophila ; Diptera ; Leptopilina boulardi ; Cynipidae ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé D. melanogaster (Meigen) a été utilisé pour tester la capacité des lignées isofemelles à conserver la variabilité génétique d'une population naturelle. Deux types d'expériences ont été réalisées. L'une a consisté à déterminer la variabilité génétique de 3 locus enzymatiques pour 32 lignées isofemelles à la première et à la 23ème génération d'élevage au laboratoire. L'autre a consisté à tester la capacité des larves à éliminer un parasitoïde par le processus d'encapsulation après 8 années d'élevage au laboratoire. D'une façon générale, certaines lignées isofemelles perdent de la variabilité durant les 23 générations de l'étude. Mais la fréquence globale des allèles reste inchangée si l'on considère l'ensemble des 32 lignées. Le seul allèle rare observé a également été conservé. Les modifications des fréquences allèliques à chacun des locus ont lieu de façon indépendante les unes des autres. La variabilité génétique d'un caractère biologique, la capacité des larves à encapsuler le parasitoïde, a également varié, mais elle a pu être restaurée à un niveau proche de la population initiale en rassemblant plusieurs individus de chacune des lignées.
    Notes: Abstract Drosophila melanogaster (Meigen) was used to test the power of isofemale lines in preserving genetic variability. We performed experiments in two ways. One series consisted of measuring the genetic variability for three enzymatic loci in 32 isofemale lines, in the first and 23rd generations of culture. In the second series, we tested the capacity of the larvae to eliminate a parasitoid by encapsulation after eight years of laboratory breeding. In general, individual isofemale lines appeared to change during the 23 generations of the study, but the global frequency of these alleles among the 32 isofemale lines stayed relatively unchanged. The only rare allele observed was also conserved. Changes in allozyme frequencies at any one locus were independent of those at other loci. Genetic variation of a biological trait, the capacity of the larvae to encapsulate a parasitoid, also changed, but it could be restored to a level close to that of the starting population by mass hybridizing together individuals of each line.
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  • 97
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    Entomologia experimentalis et applicata 66 (1993), S. 171-177 
    ISSN: 1570-7458
    Keywords: Hymenoptera ; egg parasites ; parasitoid quality ; mass rearing ; biological control ; factitious host
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the index of female's size, hind tibia length (HTL), and selected fitness parameters used in quality assessment of mass-rearedTrichogramma spp. (Hymenoptera, Trichogrammatidae) was investigated. The studied fitness parameters were: the number of mature eggs present in the ovaries of females 0–2 hours, as well as 1, 2 and 3 days old, lifetime fecundity, fecundity during a 24 h period, longevity in the presence and absence of the factitious host (Ephestia kuehniella Zeller) and locomotor activity. The relationship between HTL and fitness parameters was analysed in 7 strains ofTrichogramma spp. (Trichogramma dendrolimi Matsumura,T. evanecens Westwood,T. maidis Pinturea et Voegelé andT. ostriniae Pang et Chen) using linear correlation. No significant relationship was found between HTL and egg complement, fecundity, longevity and locomotor activity. The results indicate that HTL used as an index of female's size is not suitable for quality assessment ofTrichogramma reared onE. kuehnieIla.
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  • 98
    ISSN: 1572-8889
    Keywords: Hymenoptera ; Leptopilina ; Drosophila ; semiochemicals ; kairomones ; parasitoid ; generalist ; specialist ; foraging behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Foraging parasitoids are thought to need more specific information than generalists on the presence, identity, availability, and suitability of their insect host species. In the present paper, we compare responses to host kairomones by two phylogenetically related parasitoid species that attack Drosophilidae and that differ in the width of their host range. As predicted, the behavioral response of the parasitoids to host kairomones reflected their difference in host range. The response of the specialist parasitoid Leptopilina boulardiwas restricted to contact kairomones from its natural hosts and one closely related species. In contrast, the generalist parasitoid Leptopilina heterotomaresponded to contact kairomones of a variety of Drosophilidae species.
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  • 99
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    Journal of insect behavior 6 (1993), S. 737-750 
    ISSN: 1572-8889
    Keywords: sex pheromone ; vibrational communication ; courtship sequence ; Hymenoptera ; Braconidae ; Cotesia rubecula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The courtship behavior of the parasitic wasp Cotesia rubeculawas studied in a flight tunnel using standard quantitative ethological techniques. Emission of a female sex pheromone induces searching and signaling behavior in males. Males combine wing-fanning, which produces low-frequency airborne sound, with “pulsing” behavior, which transmits a vibrational signal through the substrate to the female and induces her receptivity. Female receptivity is indicated by a stereotyped antennal position, which may provide a visual or tactile signal to courting males. Comparison of successful and unsuccessful courtships indicated that courtship success was dependent primarily on the effective production or reception of the male pulse signal. Overall, the sequence of courtship behavior was similar to that reported for other parasitic wasps.
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  • 100
    ISSN: 1572-8889
    Keywords: Phoridae ; Diptera ; Formicidae ; Hymenoptera ; host ; parasitoid ; behavior ; Atta ; Neodohrniphora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study examines the oviposition behavior of the phorid parasitoid Neodohrniphora curvinervisand the antiparasitoid defense behavior of its leafcutting ant host Atta cephalotes. N. curvinervisfemales are diurnal sit- and- wait parasitoids that attack only outbound foragers of head width 1.6 mm or greater. Females deposit a single egg through the foramen magnum of each host successfully parasitized. Pursuit of hosts is usually initiated when an outbound forager of acceptable size passes by a parasitoid perch site. Individual foragers defend themselves against pursuing parasitoids by outrunning them along the foraging trail or by standing their ground and fending them off with their legs,antennae, and mandibles. At the colony level, susceptible foragers are protected against parasitism by a shift in the forager size distribution toward smaller unsusceptible sizes during the day when parasitoids are active and toward larger sizes at night when parasitoids are inactive. The frequency of parasitism of susceptible foragers was 15%, which is more than five times the frequency found in another system involving the phorid parasitoid Apocephalus attophilusand the leafcutting ant host Atta colombica.We offer several possible explanations for such differences in the frequency of parasitism and also examine reasons for the high incidence of superparasitism (19%) observed in the system studied.
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