Vergleichende Beobachtungen des stomatären Verhaltens verschiedener Pflanzen in Trockenrasen und Laubwäldern am Alpenostrand

Zusammenfassung Innerhalb der drei unterschiedenen Vegetationseinheiten: Trockenrasen+Felssteppen, Trockenwälder und mesophiler Laubwald wurden die Arten mit Hilfe der Infiltrationsflüssigkeiten Paraffinöl, Alkohol und Xylol auf ihr stomatäres Verhalten während der ganzen Vegetationsperiode untersucht und in die drei Verhaltenstypen starke, schwache und wechselnde Schließtendenz eingeordnet. Um standörtliche Unterschiede herauszuarbeiten, wurde aus den an einem bestimmten Wuchsort während einer bestimmten Zeit an möglichst vielen verschiedenen Pflanzen gewonnenen Infiltrationswerten jeweils ein Infiltrations-Mittelwert gebildet und außerdem, sofern Tages- und Nachtwerte von demselben Wuchsort vorlagen, auch ein Quotient aus (womöglich) höchstem Infiltrations-Mittelwert des Tages durch (womöglich) tiefsten Infiltrations-Mittelwert der Nacht (Q _T Q _N ) gebildet, um damit die Intensität der Spaltenbewegung an verschiedenen Standorten zu erfassen. Es ergab sich im allgemeinen bei trockenem Wetter und an trockenen Standorten ein intensiveres Spaltenspiel mit stärkerer nächtlicher Schließtendenz als bei feuchterem Wetter bzw. an feuchteren Standorten. Ausnahmen werden auf S. 598 erörtert.Was die standörtliche Verteilung der stomatären Verhaltenstypen betrifft, so überwiegen in der untersuchten Vegetation des behandelten Gebietes überall die Arten mit wechselnder Schließtendenz, während solche mit schwacher nächtlicher Schließtendenz im Trockenrasen überhaupt fehlen und auch im Wald nur eine sehr geringe Rolle spielen, im Gegensatz zu feuchteren Gebieten bzw. Standorten. Die Arten mit starker nächtlicher Schließtendenz sind im Trockenrasen verhältnismäßig am häufigsten.     

Physiologische Untersuchungen an einer ungewöhnlich säureresistenten Chlorella

Summary The influence of the hydrogen-ion concentration on the growth and metabolism of a highly acid-resistant green alga, Chlorella ellipsoidea (strain Marburg St), was studied. Chlorella pyrenoidosa (Emerson strain) served as a normal control organism. Growth of Chlorella ellipsoidea occurs in the entire range from Ph 2.0 to Ph 10, whereas for Chlorella pyrenoidosa the limits were found to be Ph 3.5 and Ph 10. Respiration is much less sensitive to hydrogen-ion concentration in the acid-resistant as compared to the normal strain. Thus an increase in acidity from Ph 4.0 to Ph 2.0 increases the respiratory oxygen uptake by 120% in Chlorella pyrenoidosa and by 25% in Chlorella ellipsoidea. In addition, only the less resistant Chlorella pyrenoidosa shows an accumulation of nitrite in the dark in acid culture media, indicating a disturbance of the normal course of nitrate reduction under these conditions. On the other hand, the rate of photosynthesis of both organisms was found to be almost independent of acidity between Ph 4.0 and Ph 2.0. At the acid and alkaline limits of growth in both algae, an inhibition of cell division leads to an increase of cell size and dry weight per cell, frequently connected with the occurrence of bizarre giant cells. — In addition, adaptation phenomena were found to play a role in determining the acid limit of growth. Cells of Chlorella ellipsoidea, after inoculation from normal medium (Ph about 6) into a solution of Ph 2.0, begin growth at a high rate only after a lag of about two weeks. Cells grown previously in an acid medium, however, immediately resume growth upon inoculation into a medium of Ph 2.0. This adaptation involves a considerable reduction of cell size.     

Electron Microscopy of Peripheral Nerves and Neuromuscular Junctions in the Wasp Leg

The peripheral nerve branch innervating the femoral muscles of the common yellow jacket (Vespula carolina) has been found to possess a thick lemnoblast basement membrane and a complex mesaxon. The term "tunicated nerve" is proposed to designate the type of peripheral nerve in which one or several axons are loosely mantled by meandering, cytoplasm-enclosing membranes of the lemnoblast. The peripheral axon courses longitudinally in a groove in the muscle fiber between the plasma membrane of the muscle fiber and a cap formed by lemnoblast and tracheoblast. The junction is characterized by apposition of plasma membranes of axon and muscle fiber, abundant mitochondria, and synaptic vesicles in the axon, and aggregates of "aposynaptic granules" plus mitochondria and endoplasmic reticulum on the muscle side of the synapse. Unlike the vertebrate striated muscle fiber, no complex infolding of the synapsing plasma membrane of the muscle fiber occurs. The "connecting tissue" of the insect is formed by tracheoblasts, their basement membranes, and the basement membranes of other cells. Further mechanical support is given by the ramifying tracheoles. The physiologic roles of the specialized structures are considered.     

Benzothiadiazole induces disease resistance in Arabidopsis by activation of the systemic acquired resistance signal transduction pathway

Benzothiadiazole (BTH) is a novel chemical activator of disease resistance in tobacco, wheat and other important agricultural plants. In this report, it is shown that BTH works by activating SAR in Arabidopsis thaliana. BTH-treated plants were resistant to infection by turnip crinkle virus, Pseudomonas syringae pv ‘tomato’ DC3000 and Peronospora parasitica. Chemical treatment induced accumulation of mRNAs from the SAR-associated genes, PR-1, PR-2 and PR-5. BTH treatment induced both PR-1 mRNA accumulation and resistance against P. parasitica in the ethylene response mutants, etr1 and ein2, and in the methyl jasmonate-insensitive mutant, jar1, suggesting that BTH action is independent of these plant hormones. BTH treatment also induced both PR-1 mRNA accumulation and P. parasitica resistance in transgenic Arabidopsis plants expressing the nahG gene, suggesting that BTH action does not require salicylic acid accumulation. However, because BTH-treatment failed to induce either PR-1 mRNA accumulation or P. parasitica resistance in the non-inducible immunity mutant, nim1, it appears that BTH activates the SAR signal transduction pathway.     

The leaf peroxisomal form (MFP IV) of multifunctional protein functioning in fatty-acid β-oxidation

We have purified for the first time from green leaves a multifunctional protein (MFP) involved in fatty acid -oxidation. The protein, designated MFP IV, was extracted from green leaves of three-week-old cucumber (Cucumis sativus L.) plants. Chromatography on cation exchanger, separation on hydroxylapatite, and fast-protein liquid chromatography on Phenylsuperose led to a more than 7000-fold purification and to the isolation of an apparently homogeneous 80-kDa monomeric protein. This protein is immunologically related to the glyoxysomal MFP II, as evidenced by immunodecoration with antiserum raised against MFP II. Comparison of molecular masses of all MFPs presently known revealed that the MFP prepared from green leaves (MFP IV) is distinct from MFP II (76.5 kDa) and MFP I (74 kDa) from dark-grown cotyledons. By including other properties in this comparison, we demonstrated that MFP IV can also be distinguished from the glyoxysomal MFP III (81 kDa) and the bacterially expressed MFP-a (80 kDa). Moreover, MFP IV is a constituent of leaf peroxisomes and contains the activities of 2-enoyl-CoA hydratase (EC 4.2.1.17),l-3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35) and 3-hydroxyacyl-CoA epimerase.Abbreviation MFP multifunctional protein This work was supported by grants from the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.     

ent-Kaurene biosynthesis in a cell-free system from wheat (Triticum aestivum L.) seedlings and the localisation of ent-kaurene synthetase in plastids of three species

A cell-free system capable of converting [¹⁴C]geranylgeranyl diphosphate to ent-[¹⁴C]kaurene and to an unidentified acid-hydrolysable compound was obtained from the basal portions of 5-d-old shoots of wheat seedlings (Triticum aestivum L.). By means of marker enzyme activities, the synthesis of ent-kaurene and the unknown compound could be quantitatively assigned to a plastid fraction obtained by Percoll-gradient centrifugation of the homogenate. The enzyme activities were located within the plastids, probably in the stroma, because they withstood trypsin treatment of the intact plastids, and the plastids had to be broken to release the activity, which was then obtained in soluble form. Plastid membranes had no activity. Plastid stroma preparations obtained from pea (Pisum sativum L.) shoot tips and pumpkin (Cucurbita maxima L.) endosperm also yielded ent-kaurene synthetase activity, but did not form the unknown compound. The exact nature of the active plastids was not ascertained, but the use of methods for proplastid isolation was essential for full activity, and the active tissues are all known to contain high proportions of proplastids, developing chloroplasts or leucoplasts. We therefore believe that ent-kaurene synthesis may be limited to these categories. Mature chloroplasts from the wheat leaves did not contain ent-kaurene synthetase activity and did not yield the unknown component. Incorporation of [¹⁴C]geranylgeranyl diphosphate into ent-[¹⁴C]kaurene and the unknown component was assayed by high-performance liquid chromatography with on-line radiocounting. ent-[¹⁴C]Kaurene was identified by Kovats retention index and full mass spectra obtained by combined gas chromatography-mass spectrometry. The unknown component was first believed to be copalyl diphosphate, because it yielded a compound on acid hydrolysis, which migrated like copalol on high-performance liquid chromatography and gave a mass spectrum very similar to that of authentic copalol. However, differences in the mass spectrum and in retention time on capillary gas chromatography excluded identity with copalol. Furthermore, the unhydrolysed compound was not converted to ent-kaurene by a cell-free system from C. maxima endosperm as copalyl diphosphate would have been.Abbreviations ADH alcohol dehydrogenase - AMO 1618 2isopropyl-4-(trimethylammoniumchloride)-5-methylphenyl piperi-dine-1-carboxylate - BSA bovine serum albumin - DTT dithioth-reitol - GA_n gibberellin A_n - GAPDH NADP⁺-glyceraldehyde 3-phosphate dehydrogenase - GC-MS combined gas chromatography-mass spectrometry - GGPP all trans-isomer of geranyl-geranyl diphosphate - KS ent-kaurene synthetase - MDH malate dehydrogenase - MAA mevalonate activating activity - SOR shikimate oxidoreductase We thank Mrs. Gudrun Bodtke and Mrs. Dorothee Dasbach for able technical assistance, Prof. L.N. Mander (Australian National University, Canberra, Australia) for ent-[²H₂]kaurene and Dr. Yuji Kamiya (RIKEN, Saitama, Japan) for geranylgeraniol and copalol. The work was supported by the Deutsche Forschungsgemeinschaft.     

Cytochrome b 558 and hydrogen peroxide production in small intensely fluorescent cells of sympathetic ganglia

 Small intensely fluorescent (SIF) cells are paraganglionic cells derived from sympathicoblasts which may serve as interneurons, endo-/paracrine cells or arterial chemoreceptors within sympathetic ganglia. Like paraganglionic cells of other locations, e.g., carotid body glomus cells, they are responsive to hypoxia. Recent studies on glomus cells and other hypoxia-sensing cells suggested the involvement of a b ₅₅₈ -type cytochrome and intracellular generation of H₂O₂ in the process of oxygen sensing. In the present study, we demonstrate the occurrence of the small subunit of cytochrome b ₅₅₈ , p22phox, in SIF cells of guinea-pig sympathetic ganglia by immunohistochemistry using two different antisera. H₂O₂ production was monitored in explanted intact superior cervical ganglia of 2-day-old rats by confocal laser scanning analysis of rhodamine 123 fluorescence generated due to oxidation of dihydrorhodamine 123 by H₂O₂. Using this technique, SIF cell clusters appeared as sites of highest H₂O₂ production within the ganglia. Thus, SIF cells exhibit two key features of an oxidase system generating reactive oxygen species. This may be involved in the proposed chain of events in oxygen sensing, but alternative cellular functions of this system have also to be considered. Accepted: 19 September 1996     

Characterization of monoclonal antibodies recognizing three distinct, phosphorylated carbohydrate epitopes in the lipopolysaccharide of the deep rough mutant I-69 Rd−/b+ of Haemophilus influenzae

Monoclonal antibodies against the lipopolysaccharide (LPS) of the deep rough mutant I-69 Rd⁻/b⁺ of Haemophilus influenzae were obtained after immunization of mice with sheep erythrocytes which had been coated with de- O -acylated LPS. Characterization of antibodies was performed by enzyme immuno assay (EIA) using LPS or neoglycoconjugates containing partial structures of LPS as solid-phase antigens and by haemagglutination with sheep erythrocytes coated with de- O -acylated LPS. Binding data were confirmed by EIA inhibition experiments using deacylated LPS or synthetic partial structures thereof. Three antibodies were specific for 3-deoxy- d - manno -octulopyranosonic acid- (Kdo) 5-phosphate, one for Kdo-4-phosphate, and one required, in addition to a Kdo-phosphate, parts of the phosphorylated glucosamine backbone of lipid A. All antibodies also bound in (i) Western blots to bacterial whole-cell lysates or isolated LPS separated by SDS–PAGE, (ii) bacterial colony blots, and (iii) immunofluorescence with live bacteria. The latter result indicated that Kdo-4- and Kdo-5-phosphate are synthesized by the bacteria and are not the result of phosphate migration.     

Structural organization and epithelial cell types of the intestinal diverticula (protopancreas) of ammocoetes of southern hemisphere lampreys: functional and phylogenetic implications

Larvae of the two southern hemisphere lamprey genera, Mordacia and Geotria, possess one and two intestinal diverticula, respectively, each originating at the oesophageal-intestinal junction. These diverticula comprise an inner layer of simple columnar epithelium composed solely of zymogen and mucous cells, a middle layer consisting mainly of a blood sinus, and an outer serosa layer covered by a simple squamous epithelium (mesothelium). The inner surface is highly folded only in Mordacia. The secretion of mucus probably protects the epithelium from the effects of digestive enzymes secreted by the zymogen cells and/or bile, which enters the diverticulum at its tip. Unlike the situation in southern hemisphere lampreys, the zymogen cells of the larvae of holarctic lampreys are located in the anterior intestine, a condition considered to be primitive. It is thus proposed that intestinal diverticula were developed during the evolution of southern hemisphere lampreys. The relocation of zymogen cells in the diverticula increases the area for these cells, and thus the capacity for the synthesis and secretion of digestive enzymes, particularly in Mordacia where the inner surface is folded.