Zur Biochemie und Regulation des heteromorphen Generationswechsels der Grünalge Derbesia-Halicystis

Summary During the life cycle of the green marine alga Derbesia marina-Halicystix ovalis, a diploid filamentous sporophyte called Derbesia alternates with a haploid spherical gametophyte called Halicystis. Beside this wild type a so-called mutant and a parthenogenetic enogenetic form stand at our disposal. The mutant is a haploid form with a Derbesia-like morphology. The morphology of the parthenogenetic form is also very similar to that of Derbesia. Biochemically sporophyte and gametophyte are characterized by a different cell-wall composition and enzyme pattern. The main polysaccharide of the cell wall of the sporophyte (Derbesia) is a mannan, whereas the cell wall of the gametophyte is built up mainly of glucose- and xylose-containing polysaccharides. The cell wall composition of the mutant is nearly identical with that of the Derbesia wild type. On the other hand the parthogenetic form lies to a certain degree between Derbesia and Halicystis with respect to its cell wall composition. Differences in enzyme pattern exist especially in the enzymes of GDPM- and mannan synthesis. These enzymes are present in high activities in Derbesia, the mutant, and the parthogenetic form but are absent or present only with very small activities in Halicystis. From these results we conclude that the differences in morphology, cell wall composition and enzyme pattern between the sporophyte (Derbesia) and the gametophyte (Halicystis) are brought about by a relatively stable pattern of gene activity which is changed only during the formation or the out-growth of the zoospores and the formation or fusion of gametes (see discussion).

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Abkürzungen ADPG-Pyr Adenosindiphosphat-glucose-Pyrophosphorylase E.C.2.7.7.b - F-6-P Fructose-6-phosphat - GDPM Guanosindiphosphat-mannose - GDPM-Pyr GDPM-Pyrophosphorylase E.C. 2.7.7.13 - Gluconat-6-P-DH Gluconat-6-phosphat-Dehydrogenase E.C-1.1.1.44 - G-1,6-P Glucose-1,6-diphosphat - G-6-P-DH Glucose-6-phosphat-Dehydrogenase E.C. 1.1.1.49 - M-1-P Mannose-1-phosphat - M-1,6-P Mannose-1,6-diphosphat - PGI Phosphoglucose-Isomerase E.C. 5.3.1.9 - PGM Phosphogluco-Mutase E.C. 2.7.5.1 - PMI Phosphomannose-Isomerase E.C. 5.3.1.8 - PMM Phosphomannose-Mutase - TRAP Triäthanolamin-Puffer - UDPG Uridindiphosphat-glucose - UDPG-DH UDPG-Dehydrogenase E.C. 1.1.1.22 - UDPG-4-Epi UDPG-4-Epimerase E.C. 5.1.3.2 - UDPG-Pyr UDPG-Pyrophosphorylase E.C. 2.7.7.9 - UDPXyl Uridindiphosphat-xylose     

Regulation der Entwicklung und des Stoffwechsels der Grünalge Urospora durch die Temperatur

Summary In the life cycle of Urospora wormskioldii (Mert. in Hornem) Rosenv. and U. vancouveriana (Tilden) Setschell and Gardner unbranched monosiphonous filaments (exceeding 15 cm in length) alternate with microscopic dwarf plants and a unicellular Codiolum stage. The interrelationship between these very different forms and the regulating effect of temperature on this life cycle are shown in Fig. 1. Beyond the morphological differences between the three forms there are large differences in the composition of the cell wall (Fig. 2). While the cell wall of the Codiolum stage is mainly built up of mannans, glucose-containing polysaccharides predominate in the cell wall of the dwarf plants and xylose-containing polysaccharides are abundant in the cell wall of the filamentous plants. Differences in metabolism between dwarf plants and filamentous plants were detected by ¹⁴CO₂-incorporating experiments. On the basis of chlorophyll content dwarf plants have a higher total ¹⁴CO₂-fixation rate than filamentous plants cultured at either 2°C or 14°C (Fig. 3). Furthermore, a higher rate of synthesis for Calvin-cycle intermediates and other metabolites was generally demonstrated in dwarf plants with one important exception: Uridine diphosphate glucose was synthesized faster in filamentous plants cultured at 2° C (Fig. 4). Studies of ¹⁴CO₂-incorporation in filamentous plants cultivated at 2° C or 14° C (at the higher temperature filamentous plants survive only for a limited time) revealed that the latter show a much higher incorporation of ¹⁴C into insoluble substances than the former. On the other hand, pools of soluble substances — especially Calvin-cycle intermediates — are much smaller in 14° C-plants than in 2° C-plants with the exception of that of sucrose, which is accumulated in 14° C-plants in high amounts (more than 70% of the total radioactivity in soluble compounds, Fig. 5). These facts may be explained by temperature-sensitive differential gene expression and/or steps in metabolism (see discussion).

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Abkürzungen F-6-P Fructose-6-phosphat - F-1,6-P Fructose-1,6-diphosphat - Gal Galactose - Glc Glucose - G-6-P Glucose-6-phosphat - Man Mannose - PEP Phosphoenolpyruvat - 3 PGS 3-Phosphoglycerinsäure - Rham Rhamnose - UDPG Uridindiphosphat-glucose - Xyl Xylose Biologische Anstalt, D-2192 Helgoland.     

Nachweis von Enzymen des Galactosestoffwechsels in der Grünalge Acetabularia mediterranea

Summary The reason for interest in the galactose metabolism of the unicellular green alga Acetabularia mediterranea lies in the question of how the different galactose content in the cell wall of the stalk and the cap is formed. The galactose content is low in the cell wall of the stalk and high in the membrane of the cap (Werz, 1963). Progress in this question presupposes information about the enzymes of galactose metabolism in this organism. The occurrence of the whole series of enzymes which are concerned with the synthesis of UDP-galactose from fructose-6-phosphate could be demonstrated. These enzymes are as follows: Phosphoglucose-isomerase [E.C.5.3.1.9], phosphoglucomutase [E.C.2.7.5.1], UDP-glucose pyrophosphorylase [E.C.2.7.7.9], UDP-glucose-4-epimerase [E.C.5.1.3.2], nucleosidediphosphate kinase [E.C.2.7.4.6] and inorganic pyrophosphatase [E.C.3.6.1.1].

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Nachweis von Enzymen des Galactosestoffwechsels in der Grünalge Acetabularia mediterranea

Zusammenfassung In der einzelligen Grünalge Acetabularia mediterranea konnten die für die Synthese von UDP-galactose aus Fructose-6-phosphat notwendigen Enzyme Phosphoglucose-Isomerase, Phosphoglucomutase, UDP-glucose-Pyrophosphorylase und UDP-glucose-4-Epimerase nachgewiesen werden, außerdem Nucleosiddiphosphat-Kinase und anorganische Pyrophosphatase. Der Galactosestoffwechsel von A. mediterranea ist deshalb von Interesse, weil Stiel- und Hutmembran einen unterschiedlichen Galactosegehalt aufweisen.

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Herrn Professor Dr. J. Hämmerling zum 65. Geburtstag gewidmet.     

CO2-Gaswechsel amphistomatischer Blätter

Summary The leaves of Primula palinuri and Zea mays are amphistomatic. The CO₂-exchange of both leaf surfaces was measured separately. The distribution of stomata and the portion of CO₂-uptake of both leaf surfaces correspond well. In Primula the greater part diffuses through the upper surface of the leaf, in Zea through the lower surface. Stripping of the Primula epidermis does not change the total CO₂-uptake but the greater part now diffuses through the lower stripped surface of the leaf. The CO₂-uptake of the upper surface alone, as well as of the lower surface alone and of both surfaces together was measured. The quantities of CO₂ transported through the leaf surfaces are not independent of each other: if CO₂-uptake is only possible through one surface of the leaf the CO₂ flux on this side increases. The significance of this property of amphistomatic leaves in relation to transpiration and CO₂ assimilation is discussed.     

Spurenelementdüngung und Wasserhaushalt einiger Kulturpflanzen

Ohne Zusammenfassung     

CO2-Gaswechsel amphistomatischer Blätter

Summary The time-response of the CO₂-exchange of both leaf surfaces was measured separately. Leaves of Primula palinuri and Zea mays were used for the study. After short dark-periods (3 min) the stomata are not closed. Consequently CO₂-uptake starts quickly after re-illumination and reaches the steady-state value very rapidly. The time-response of stripped leaves of Primula and of normal leaves after short dark-periods is identical. Accordingly, the conclusion seems to be evident that in both cases we are measuring the time-response of photosynthesis, which is not influenced by stomatal reactions. After long dark-periods (60 min) the stomata are closed. After re-illumination the CO₂ released by respiration is immediately reassimilated. There is a distinct lag-phase in time-response which is more or less located in the CO₂-compensation point. This lag-phase is of different length for both leaf surfaces, and is interpreted as being the lag-phase of stomatal opening reactions. The consequence of the observed different time response of photosynthesis and stomatal reactions is discussed: under non-steady-state conditions photosynthesis is limited by slow stomatal opening reactions.     

Wärmeresistenz und chemische Resistenz der GrünalgeGloeococcus bavaricus Skuja

Ohne Zusammenfassung     

Phylogenetische Beziehungen in der GrünalgengattungAcrosiphonia

Zusammenfassung 1. Fakultative Karyogamie konnte bei keiner der untersuchtenAcrosiphonia-Arten nachgewiesen werden. Alle Arten mit geschlechtlicher Fortpflanzung können sich zusätzlich durch zweigeißelige Schwärmer vermehren.2.Acrosiphonia spinescens hat heteromorphen Generationswechsel; der Sporophyt ist Codiolum-artig, der monözische Gametophyt fädig. Unverschmolzene zweigeißelige Schwärmer entwickeln sich ebenfalls zum Codiolum-Stadium, in seltenen Fällen auch direkt zu fädigen Pflanzen.3. Dieser wie auch Punkt 5 sind keine Ergebnisse der vorliegenden Studie, ihr Inhalt ist aber für das Verständnis der Zusammenhänge notwendig. Die isländischeA. grandis hat keinen Generationswechsel, jedoch vereinigt ihr Thallus heteromorphe Bauelemente. Das aus der Zygote zunächst entstehende typischeCodiolum wächst im 16-Kern-Stadium — vermutlich nach vollzogener Reduktionsteilung — unmittelbar zur fädigenAcrosiphonia aus. Die Entwicklung zweigeißeliger Schwärmer zeigt keine morphologischen Unterschiede (Kornmann 1970).4. AuchAcrosiphonia arcta hat keinen Generationswechsel; die zygotische Phase beschränkt sich auf die erste Zelle ihres fädigen Thallus. Nach wahrscheinlich meiotischer Teilung vierkernig geworden, wächst die Zygote zum fädigen Thallus weiter. Keimlinge aus zweigeißeligen Schwärmern werden nach der ersten Kernteilung zweizellig, ihre weitere Entwicklung gleicht der aus Zygoten.5.Acrosiphonia sonderi pflanzt sich ausschließlich durch ungeschlechtliche zweigeißelige Zoosporen in gleicher Weise fort, wie dies beiA. arcta undA. spinescens zusätzlich der Fall ist (Kornmann 1962b).6. DieAcrosiphonia-Arten mit geschlechtlicher Fortpflanzung zeigen eine stufenweise Reduktion der Diplophase von einer absoluten über eine zeitlich begrenzte Selbständigkeit bis zur völligen Einbeziehung in einen einheitlichen Organismus. Die Fähigkeit unverschmolzener Schwärmer, sich direkt zu entwickeln, verbindet diese Arten mit denen ohne geschlechtliche Vermehrung.7. Die Kenntnis der Lebenszyklen derAcrosiphonia-Arten bildet die Grundlage für eine systematische Gliederung der Gattung, deren Arten in vielen Fällen kennzeichnender morphologischer Unterschiede ermangeln.

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Phylogenetical relationships in the chlorophycean genusAcrosiphonia

Plasmogamic parthenogenesis and facultative caryogamy have been introduced as new definitions into literature on algal development byJónsson (1964a, b). In his studies on life cycles ofAcrosiphonia incurva andA. spinescens, he expresses the opinion that mating of gametes must not necessarily be followed by fusion of their nuclei. Only true zygotes give rise to unicellular sporophytes, whereas nuclei of false zygotes are separated by a cross-wall in the germinating cell, resulting in a mictohaplontic gametophyte.Jónsson (1967) described facultative caryogamy also in an Icelandic species, identified by him as Acrosiphonia sonderi. Recently,Jónsson (1968a) interpreted the succession of isomorphic generations in the Helgolandian speciesAcrosiphonia arcta by plasmogamic parthenogenesis, caryogamy being totally suppressed. In my studies on life histories ofAcrosiphonia species, facultative caryogamy has never been observed. Four different types of life-cycles are combined to a most striking example of phylogenetical relationships within a genus. Life-history is heteromorphic inA. spinescens. Zygotes develop into an independent Codiolum-like sporophyte, its zoospores give rise to the filamentous gametophytes. Biflagellate swarmers are able to develop in the same way, but very few of them germinate directly into gametophytes. Alternation of generations is not to be found in the Icelandic speciesA. grandis (Kornmann 1970). Though its zygotes give rise to a free-living, true Codiolum-stage at first, zoospores are not produced. After increasing the number of nuclei up to 16 by simultaneous divisions, the Codiolum-like cell grows out, directly producing a filamentous plant. Unfused swarmers develop in the same way.Acrosiphonia arcta, too, lacks an alternation of generations, but a Codiolum-like stage is brought about no more. The nucleus of the zygote divides twice, a process which is supposed to represent meiosis. The enlarged zygote develops into the filamentous plant, and generations are isomorphic throughout. Germinating biflagellate swarmers behave similarly after the nucleus has divided once. InAcrosiphonia sonderi, finally, sexual reproduction does not occur. Biflagellate zoospores only are produced, which develop in the same way as has been shown in the above-mentioned examples of direct reproduction inA. arcta andA. spinescens. Two trends of phylogenetical relationships become obvious in this series ofAcrosiphonia life cycles: (1) Alternation of the heteromorphic generations is gradually reduced to a succession of isomorphic ones, in which the germinating zygote constitutes the diplontic phase. (2) Direct development of swarmers, occurring exclusively in asexually reproducing species, is rarely found in the diplohaplontic type of cycles. This pattern of life-histories represents an efficient basis for taxonomical classification in the genusAcrosiphonia, whose species often lack clear morphological characters for distinction.

     

Beiträge zur Kenntnis der gamo- und karpotropischen Blütenbewegungen der Gräser

Ohne Zusammenfassung     

Über den CO2-Gaswechsel einiger Flechten nach Wasserdampfaufnahme

Zusammenfassung Die Abhängigkeit des CO₂-Gaswechsels der Flechten Evernia divaricata, E. prunastri, Ramalina thrausta und R. farinacea vom Wassergehalt wurde untersucht. Es kann gezeigt werden, daß die im Zustand latenten Lebens befindlichen, ausgetrockneten Thalli aus nahezu wasserdampf-gesättigter Luft bis 70% ihres Trockengewichtes an Wasserdampf auf-nehmen. Diese Wasserdampfaufnahme reicht aus, um den CO₂-Gaswechsel zu reaktivieren. Die apparente CO₂-Aufnahme im Dampfdruck-gleichgewicht mit dem nahezu wasserdampfgesättigten Luftraum beträgt bei allen vier Arten etwa 90% der bei optimaler Einquellung mit tropfbarem Wasser erreichten Leistung. Reaktivierung des CO₂-Gaswechsels ist auch in nicht wasserdampfgesättigter Luft möglich, und der Kompensationspunkt des CO₂-Gaswechsels wird zwischen 80 und 85% rel. Feuchte (Sättigungsdefizit bei 10°C: 1,85-1,38 mm Hg) erreicht und überschritten.

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CO₂-exchange of some lichens after absorption of water vapour

Summary The relation between CO₂-exchange and water content of the lichens Evernia divaricata, E. prunastri, Ramalina thrausta and R. farinacea was investigated. The dry thalli absorb water vapour up to 70% of their dry weight. This uptake of water vapour is sufficient to reactivate the CO₂-exchange. In equilibrium with the vapour pressure of the nearly saturated air the apparent CO₂-uptake amounts to 90% of the value obtained after imbibition with liquid water. Even in unsaturated air the CO₂-exchange is reactivated and the compensation point is reached between 80 and 85% relative humidity (saturation deficit at 10°C: 1,85-1,38 mm Hg).

     

Pseudococcomyxa adhaerens Korshikov—eine an extreme Lebensbedingungen angepaßte kokkale Grünalge

Zusammenfassung Massenentwicklung von Pseudococcomyxa adhaerens Korshikov, einer kleinen kokkalen Chlorophycee, trat wiederholt spontan in Vorratsgefäßen für destilliertes Wasser auf. Eine Übertragung der Algen in reine MgSO₄-Lösungen (geprüft bis zu 24%) geschah ohne Schaden für den Organismus, das Wachstum war sogar stimuliert. Eine hohe cH⁺ und sehr geringe Lichtintensitäten sind Bedingung für eine gute Entwicklung der Algen unter diesen Voraussetzungen.     

Chlorosphaeropsis epidemica,spec. nova,eine neue Grünalge mit endophytischer Lebensweise

The new parasitic algaChlorosphaeropsis epidemica is a member of theChlorosarcinales and lives endophytically in the leaf-tissue ofPotamogeton species. It forms stacks of cells and appears in great numbers, especially in dying leaf-blades. Sexual reproduction is described for the first time in this genus. Apart from its endophytic way of life,Chl. epidemica is characterized by mononuclear cells with a parietal chloroplast of irregular thickness and with a few perforations, sometimes of complicated reticulate shape, and with 1–5 pyrenoids. The usually sphaerical gametes (respectively zoospores) are provided with two equal flagella, a parietal plastid, one pyrenoid and one stigma. In connection with the asexual reproduction the terms vegetative division and desmoschisis are critically discussed.

     

Protonema mit Riesenkern bei der siphonalen GrünalgeBryopsis hypnoides und weitere cytologische Befunde

Zusammenfassung 1. Die in Kulturen erhaltenen Zygoten vonBryopsis hypnoides keimen ohne Ruheperiode aus zu einem Protonema mit ein oder mehreren pfriemförmigen Ästen von begrenztem Wachstum, die sich mehr oder weniger aufrecht auf einem prostraten rhizoidalen Teil erheben.2. Im Gegensatz zu dem vielkernigen Thallus der gefiederten Alge besitzt das Protonema einen einzigen großen Kern, der den achtfachen Durchmesser der vegetativen Kerne des Fiederthallus erreichen kann. Dieser Riesenkern enthält einen langgewundenen Nucleolus, der in Gestalt und Entwicklung Ähnlichkeit mit dem Nucleolus des Riesenkerns vonAcetabularia besitzt. Im Nucleolus wurde RNS nachgewiesen.3. Das Protonema wird vielkernig vor der Entstehung ein bis mehrerer breiterer Triebe, die sich zu den bekannten Fiederthalli oder zu Rhizoiden ausbilden.4. Das Teilungsbild des Riesenkerns wird von einer hantelförmigen Spindel des sich teilenden Nucleolus beherrscht, an deren Peripherie eine Mitose diploider Größenordnung zu erkennen ist. Der Riesenkern löst sich anschließend auf und entläßt nacheinander 2 Sekundärkerne, die sich mitotisch vermehren.5. Der relativ große Nucleolus der Thalluskerne bleibt ebenso wie die Kernmembran während der Mitose erhalten. Er wird in der Anaphase stark gestreckt, und die Verbindung zwischen den Tochternucleolen löst sich oft erst in der Telophase.6. Während der Gametenbildung in den Fiedern wird die Chromosomenzahl von 2n=16 auf n=8 reduziert.7. Anisogame Kopulation wurde beobachtet.

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Protonema with giant nucleus in the siphonaceous green algaBryopsis hypnoides and additional cytological results

Zygotes ofBryopsis hypnoides, maintained in modified Schreiber-solution, germinate into a rhizoidal protonema with a single nucleus; the nucleus diameter increases up to eight times that of vegetative nuclei in the multinucleate thallus. The giant nucleus contains a long sinuous nucleolus similar to that ofAcetabularia. The protonema becomes multinucleate prior to the formation of the plumose thalli. The division of the giant nucleus has been observed: Chromosomes in mitotic configuration, apparently diploid, become visible at the periphery of a large dumbbell-shaped spindle formed by the dividing nucleolus. Subsequently, the giant nucleus dissolves and dismisses two small nuclei, which propagate mitotically. Further observations deal with the persistence of the nucleolus during mitosis, chromosome number, gamete formation, and gamete copulation.