Elektronenmikroskopische untersuchungen an den Guanin-Speicherzellen von Araneus diadematus clerck (Araneae,Araneidae)

Zusammenfassung Bei einigen Spinnen, vor allem aus der Familie der Araneidae, bilden funktionell umgewandelte Mitteldarmzellen unmittelbar unter der Hypodermic eine nahezu geschlossene Zellschicht, die mehr oder minder stark mit Guaninkristallen angefiillt sein kann.Die distalen Zellbereiche dieser von uns als Guanocyten bezeichneten Zellen verzahnen rich mit der Hypodermis selbst oder stehen mit dem schmalen hypodermalen Hämolymphsinus in Verbindung. Thre proximalen Enden sind lang ausgezogen und schieben sich zwischen nicht umgewandelte Resorptionszellen. Jede Guanocyte steht mit dem Mitteldarmlumen in direkter Verbindung.Auf Grund des Organellenbestandes sind die Guanocyten als spezialisierte Mitteldarmzellen auzusprechen, die während der reproduktiven Periode die übrigen exkretorisch tätigen Gewebe bzw. Organe unterstützen oder ergänzen, indem sie der Hämolymphe, der Hypodermis und den benachbarten Resorptionszellen pinocytotisch purinhaltige Abbauprodukte und andere Exkrete entnehmen. Dieselben werden unter Mitwirkung eines glatten endoplasmatischen Retikulums umgebaut und temporär intrazellulär als kompliziert aufgebaute Kristalle innerhalb von membranösen Kristallsäckehen gespeichert.Die Notwendigkeit intrazellulärer Exkretspeicherung auf Grund der Ernährungs-physiologie und Abwandlungen in der Funktionsmorphologie sowie fortschreitender Alterungserscheinungen wird diskutiert.

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Electromicroscopic studies of the guanine storage cells of Araneus diadematus Clerck (Araneae, Araneidae)

Summary Guanocytes are present in several spiders especially of the family Araneidae. The guanocytes form a compact cell-layer under the hypodermis. Their distal parts remain connected to the hypodermic hemolymph sinus, while the proximal ends establish contact with the midgut lumen in the shape of a long cellular process.The organelle equipment of the guanocytes shows that they are specialized midgut cells. They support or replace the other excretory tissues and organs especially during the reproduction period. By pinocytosis, the guanocytes remove catabolites of the purine and protein metabolism from the hemolymph, the adjacent resorption cells of the midgut, as well as from the overlying hypodermis cells. The stored catabolites are formed into complex crystals assisted by the smooth endoplasmic reticulum.The necessity of the temporary intracellular excretory storage on the basis of the physiology of nutrition, changes in the functional morphology, and general signs of old age are discussed.

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Die Untersuchungen werden dankenswerterweise von der Deutschen Forschnungsgemeinschaft durch Sach- und Personalmittel gefördert.

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Herrn Prof. Dr. H.-U. Koecke danke ich für seine Unterstützung und die Einräumung eines Arbeitsplatzes am Elektronenmikroskop.     

Effects of Irradiance on Crassulacean Acid Metabolism in the Epiphyte Tillandsia usneoides L. (Bromeliaceae)

Spanish moss (Tillandsia usneoides L.) was collected in South Carolina, maintained in a greenhouse, then exposed to five levels of photosynthetic photon flux density (PPFD) for 3 weeks. Following this treatment, plants were sampled for chlorophyll concentrations, nocturnal acid accumulations, and photosynthetic responses to subsequent exposure at a range of PPFD. No acclimation to PPFD was observed; all plants exhibited similar patterns of nocturnal CO₂ uptake and acid accumulation regardless of initial PPFD treatment. These patterns revealed that at a PPFD level of approximately 200 micromoles per square meter per second (daytime integrated PPFD of 10 moles per square meter per day), CAM saturated or, in low-PPFD plants, was optimal. The results of this study indicate that adaptation to high PPFD is not necessarily a requirement of CAM.     

Responses of photosynthetic O2 evolution to PPFD in the CAM epiphyte Tillandsia usneoides L. (Bromeliaceae)

Past studies of the effects of varying levels of photosynthetic photon flux density (PPFD) on the morphology and physiology of the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides L. (Bromeliaceae) have resulted in two important findings: (1) CAM, measured as integrated nocturnal CO₂ uptake or as nocturnal increases in tissue acidity, saturates at relatively low PPFD, and (2) this plant does not acclimate to different PPFD levels, these findings require substantiation using photosynthetic responses immediately attributable to different PPFD levels, e.g., O₂ evolution, as opposed to the delayed, nocturnal responses (CO₂ uptake and acid accumulation). In the present study, instantaneous responses of O₂ evolution to PPFD level were measured using plants grown eight weeks at three PPFD (20–45, 200–350, and 750–800 mol m^-2s^-1) in a growth chamber, and using shoots taken from the exposed upper portions (maximum PPFD of 800 mol m^-2s^-1) and shaded lower portions (maximum PPFD of 140 mol m^-2s^-1) of plants grown ten years in a greenhouse. In addition, nocturnal increases in acidity were measured in the growth chamber plants. Regardless of the PPFD levels during growth, O₂ evolution rates saturated around 500 mol m^-2s^-1. Furthermore, nocturnal increases in tissue acidity saturated at much lower PPFD. Thus, previous results were confirmed: photosynthesis saturated at low PPFD, and this epiphyte does not acclimate to different levels of PPFD.Abbreviations ANOVA analysis of variance - CAM Crassulacean acid metabolism - DW dry weight - PPFD photosynthetic photon flux density - SNK Student-Newman-Keuls (to whom all correspondence should be sent-present address and reprint requests);     

Physiological responses of the CAM epiphyte Tillandsia usneoides L. (Bromeliaceae) to variations in light and water supply

In an effort to understand the mechanisms that sustain rootless atmospheric plants, the modulation of Crassulacean acid metabolism (CAM) in response to variations in irradiance and water supply was investigated in the epiphyte Tillandsia usneoides. Plants were acclimated to three light regimes, i.e. high, intermediate and low, with integrated photon flux densities (PFD) of 14.40, 8.64 and 4.32 mol m-2 d-1 equivalent to an instantaneous PFD of 200, 100, and 50 mumol m-2 s-1, respectively. Daily watering was then withdrawn from half of the plants at each PFD for 7 d prior to sampling. In response to the three PFD treatments, chlorophyll content increased in plants acclimated to lower irradiances. Light response curves using non-invasive measurements of chlorophyll fluorescence demonstrated that photosystem II efficiency (phi PSII) was maintained in high PFD acclimated plants, as they exhibited a larger capacity for non-photochemical dissipation (NPQ) of excess light energy than low PFD acclimated plants. Net CO2 uptake increased in response to higher PFD, reflecting enhanced carboxylation capacity in terms of phosphoenolpyruvate carboxylase (PEPc) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) activities. After water was withdrawn, nocturnal net CO2 uptake and accumulated levels of acidity declined in all PFD treatments, concomitant with increased respiratory recycling of malate. Examining the strategies employed by epiphytes such as T. usneodies to tolerate extreme light and water regimes has demonstrated the importance of physiological mechanisms that allow flexible carboxylation capacity and continued carbon cycling to maintain photosynthetic integrity.     

Systematics of Tillandsia subgenus Pseudalcantarea (Bromeliaceae)

Tillandsia subg.Pseudalcantarea (Bromeliaceae) includes four species as currently delimited. The phylogenetic relationships of the species in this group are investigated by a cladistic analysis using 16 morphological characters, withVriesea subg.Alcantarea employed as the outgroup.Tillandsia subg.Pseudalcantarea is found to be paraphyletic.Tillandsia grandis andT. paniculata are transferred toTillandsia subg.Tillandsia because they are hypothesized to share a more recent common ancestor withT. utriculata, the type of the genus, than they do with the other two species placed in subg.Pseudalcantarea, i.e.,T. baliophylla andT. viridiflora. These latter two species possibly constitute a basal clade withinTillandsia and are provisionally retained within subg.Pseudalcantarea.     

Elektronenmikroskopische Untersuchungen an den Chordazellen von Petromyzon

Zusammenfassung Die Chordazellen von 30–40 cm langen Neunaugen (Petromyzon) wurden nach Osmium- und Kaliumpermanganatfixierung elektronenmikroskopisch untersucht. Das Chordaepithel (Chordoblasten) hat ein stark ausgeprägtes endoplasmatisches Retikulum mit Paladegranulabesatz, das an das Ergastoplasma von eiweißsezernierenden Drüsenzellen erinnert. Dieses endoplasmatische Retikulum wird mit der Produktion von Tonofilamenten in Zusammenhang gebracht. In weiter zentralgelegenen Zellen werden die Tonofilamente dicht unter die Zelloberflächenmembran gelagert, so daß eine Zytoplasmarinde entsteht. Die Zellgrenzen liegen eng aneinander. Einzelne Kontaktstellen haben Desmosomen. Die blasigen Chordazellen besitzen eine stark ausgebildete Rindenschicht mit vielen Tonofilamenten, die unter der Zelloberflächenmembran liegt. Diese Rindenschicht ist dicker als 0,5 , damit im Lichtmikroskop sichtbar. Sie entspricht der sog. Zellmembran in den lichtmikroskopischen Untersuchungen. Im Innern dieser blasigen Zellen lassen sich nach Osmiumfixierung granuläre Elemente nachweisen, die sich nach Kaliumpermanganatfixierung oder Bleihydroxydkontrastierung als Glykogen darstellen. Ihre Produktion hängt auch mit dem endoplasmatischen Reticulum zusammen, das zuerst in größere Abschnitte zerfällt und dann noch seinen Paladegranulabesatz verliert. Auch die großen blasigen Zellen haben ihre Oberflächenmembran und Desmosomen. Sie müssen deshalb noch als Epithelzellen betrachtet werden.Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

气生凤梨叶片结构研究

我们以地生凤梨(Guzmnania‘Denise’)作为对照,利用扫描电镜技术、石蜡切片技术对3种气生凤梨(Til-landsia stricta‘Hard leaf’、T.stricta‘Cotton candy’与T.filifolia)的叶片表面和内部结构进行了研究。结果表明所有凤梨叶片表面均分布着葵花状的鳞片,鳞片由碟状细胞、环状细胞和翼状细胞3类细胞构成,最内部的碟状细胞通过柄状细胞与叶片内部的叶肉细胞相连。气生凤梨叶片表面鳞片白色、蜡质、密度很大,但气孔很少或不可见,暗示鳞片除吸收水分和养分外,还可能具有减少光呼吸、排水及反射阳光等功能。另外,不同的气生凤梨之间叶片表面鳞片的形态、大小和密度也不同,反映了它们对其不同起源地及现生存环境的适应。     

First record of bat-pollination in the species-rich genus Tillandsia (Bromeliaceae)

Background and Aims

Bromeliaceae is a species-rich neotropical plant family that uses a variety of pollinators, principally vertebrates. Tillandsia is the most diverse genus, and includes more than one-third of all bromeliad species. Within this genus, the majority of species rely on diurnal pollination by hummingbirds; however, the flowers of some Tillandsia species show some characteristics typical for pollination by nocturnal animals, particularly bats and moths. In this study an examination is made of the floral and reproductive biology of the epiphytic bromeliad Tillandsia macropetala in a fragment of humid montane forest in central Veracruz, Mexico.

Methods

The reproductive system of the species, duration of anthesis, production of nectar and floral scent, as well as diurnal and nocturnal floral visitors and their effectiveness in pollination were determined.

Key Results

Tillandsia macropetala is a self-compatible species that achieves a higher fruit production through outcrossing. Nectar production is restricted to the night, and only nocturnal visits result in the development of fruits. The most frequent visitor (75 % of visits) and the only pollinator of this bromeliad (in 96 % of visits) was the nectarivorous bat Anoura geoffroyi (Phyllostomidae: Glossophaginae).

Conclusions

This is the first report of chiropterophily within the genus Tillandsia. The results on the pollination biology of this bromeliad suggest an ongoing evolutionary switch from pollination by birds or moths to bats.     

Active Uptake of Amino Acids by Leaves of an Epiphytic Vascular Plant, Tillandsia paucifolia (Bromeliaceae)

Specialized epidermal trichomes on the leaves of the epiphyte, Tillandsia paucifolia (Bromeliaceae) accumulate amino acids from solution. Simultaneous net uptake of 17 amino acids was determined using high performance liquid chromatography. Uptake occurs against concentration gradients at least as high as 10⁴.     

Morphologische und physiologische untersuchungen an den intrazellularen symbionten von Pseudococcus citri Risso

Ohne ZusammenfassungHerrn Prof. Dr. Paul Buchner zu seinem 65. Geburtstag in Verehrung gewidmet.     

Elektronenmikroskopische Untersuchungen an den Tentakeln vonLanice conchilega (Polychaeta,Sedentaria)

Zusammenfassung 1. Die glatten Tentakel vonLanice conchilega Pallas wurden in bezug auf ihre Feinstruktur untersucht.2. Den äußeren Abschluß des Tentakels bildet eine Kutikula, die eine deutliche Zonierung aufweist. Der Kutikula liegt eine Schicht osmiophiler Granula auf.3. An die Kutikula schließt sich eine einschichtige Epidermis an. Diese enthält Sekret- und Sinneszellen.4. Die Sekretzellen treten gehäuft in der Tentakelspitze und weniger oft in dem übrigen Tentakel auf. Je nach Lage der Sekretzellen wird ein unterschiedliches Freiwerden der Sekrete beobachtet.5. Von der Tentakelspitze bis zum Mund verläuft eine Flimmerrinne. Eingehend wird der Feinbau der Kinocilien und ihrer Cilienwurzeln behandelt.6. Es werden drei Typen von Sinneszellen beschrieben, von denen wahrscheinlich zwei chemorezeptorische und eine mechanorezeptorische Funktionen wahrnehmen.7. Auf die Epidermis folgt ein Hautmuskelschlauch. Dieser besteht aus einer schwach ausgebildeten Ringmuskulatur und einer wesentlich stärkeren Längsmuskulatur.8. Den Abschluß zum Tentakelhohlraum bildet ein Coelothel mit vereinzelt auftretenden Coelothelwimpern.9. Die Coelomflüssigkeit enthält Coelomocyten, die dem Typ der Lymphocyten zugeordnet werden können.

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Electron microscope studies on the tentacles ofLanice conchilega (Polychaeta, Sedentaria)

The structure of the smooth tentacles inLanice conchilega Pallas was studied employing an electron microscope. The monolayered tentacle epithelium is covered by a zonated cuticle which bears a granular border. Specialized cells of the epithelium comprise secretory cells and three types of sensory cell (one mechanoreceptor and two chemoreceptors). The kinocilia of the ciliated grooves possess two types of rootlets, one of which connects the basal bodies of neighbouring cilia. Below the epithelium are located layers of circular and longitudinal muscles. The wall of the tentacle cavity is composed of a coelothelium which bears only few cilia. The coelomic fluid contains coelomocytes (lymphocytes).

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Tillandsia tomasellii (Bromeliaceae), a new species from Oaxaca,Mexico

Tillandsia tomasellii from Río Hondo, Oaxaca, Mexico, is described and compared to related speciesT. xerographica andT. fasciculata.     

Germination and Establishment of Tillandsia eizii (Bromeliaceae) in the Canopy of an Oak Forest in Chiapas, Mexico

We assessed the effectiveness of repopulating the inner canopy and middle canopy of oak trees with seeds and seedlings of the epiphytic bromeliad Tillandsia eizii. Canopy germination was 4.7 percent, considerably lower than in vitro (92%). Of the tree-germinated seedlings, only 1.5 percent survived 6 mo. In contrast, 9.3 percent of transplanted laboratory seedlings survived 15 mo. To repopulate trees, we recommend transplanting laboratory-grown seedlings, as large as practically possible, to branches in the middle canopy.