Gliding motility of Peloploca spp., and their distribution in the sediment and water column of a eutrophic lake

Observations indicating gliding motility in the gas-vacuolate, filamentous organism Peloploca were made using microcapillary tubes. Tubes containing semi-solid agar, incubated in sediment cores gave good enrichments of Peloploca spp. The organisms, which had the form of helical bundles of filaments, were seen to corkscrew through the agar at up to 2–3 m s^-1.The vertical distribution of Peloploca spp. in the sediment and water column of a eutrophic lake was examined periodically during summer stratification. The organisms were confined to anoxic conditions in the sediment prior to stratification. With increasing anoxia in the hypolimnion, the population shifted upwards in the sediment, and towards the end of stratification, in the most reducing conditions, appeared in the lower hypolimnion. Anaerobically incubated sediment cores also showed the movement of the Peloploca population from sediment into the overlying water.It is suggested that the gliding motility and helical morphology of Peloploca bundles enable them to migrate through sediment in response to oxygen and Eh gradients, in addition to their use of gas vacuoles to adjust their position in the water column. The taxonomic implications of gliding motility in Peloploca spp. are discussed.     

Das Phloem der Haustorien vonCuscuta

Summary Haustoria ofCuscuta odorata R. & P. andC. grandiflora H.B.K. show continuous traces of sieve elements, connecting the phloem of the host with that of theCuscuta shoot. The continuity of this haustorial phloem is discernible by callose fluorescence after staining with aniline blue. The fine structural criteria for sieve tubes are analyzed electronmicroscopically, with special respect to sieve pores, P-protein, and a distinct wall-standing smooth surfaced ER. Within the central part of the haustorium sieve tubes are elongated, while the elements abutting the phloem of theCuscuta shoot are nearly isodiametric in shape. Both elements are associated with rather large companion cells, derived from an unequal division.

     

Effects of polyoxin D on germination,morphological development and biosynthesis of the cell wall of Trichoderma viride

When polyoxin D is added to a spore suspension of Trichoderma viride at a concentration from 50–100 g/ml, it inhibits from 40–60% of germination. This percentage increases if dimethylsulfoxide (DMSO) is added.Mycelium growing in the presence of polyoxin D becomes irregular and loses its rigidity, showing several bulges along the hypha. Under the electron microscope the features of the cell wall and cytoplasmic content are apparently normal. Nevertheless, after incubation with different lytic systems or with (¹⁴C)glucose, it can be seen that polyoxin D partially inhibits the biosynthesis of -(1-3)glucan and the biosynthesis of chitin to a greater extent attaining inhibition of 83% at 100 g/ml of the antibiotic concentration.Regenerating protoplasts are less affected by polyoxin D. They do regenerate slower but the percentage of regeneration is more than 80%. Aberrant tubes synthesized by these protoplasts are not affected, they manifest their usual morphology and lack of chitin is confirmed in their composition.List of Abbreviations CECT Colecci Española de Cultivos Tipo - GAE Glucose, Asparagine and yeast Extract - DMSO Dimethylsulfoxide - PPO Diphenyloxazole - POPOP 1,4-bis-(4-methyl-5-phenyloxazol-2-yl)     

Quinacrine-induced dilation of the rat cecum and degeneration of large granular vesicle-containing neurons in the myenteric plexus

Summary An electrophoretic analysis of the microtubule-containing transport channels, known as nutritive tubes, which link the nutritive cells with the chain of developing oocytes in the telotrophic ovarioles of the hemipteran Notonecta glauca, has been carried out. The major polypeptide components resolved have been identified tentatively as -and -tubulin subunits by their comparable electrophoretic mobility to tubulin subunits from purified mammalian brain microtubule protein. Co-migration of some of the minor components with proteins resolved from insect ribosomes (which are the only other components of the nutritive tubes as seen in ultrastructural studies) indicates that these may be ribosomal proteins. Also characterized by electrophoresis were the nutritive cells, which are the source of synthesis of the components transported via the nutritive tubes, and the oocytes, the sites of their accumulation.     

Lifetime and temporal occurrence of ectomycorrhizae on ponderosa pine (Pinus ponderosa Laws.) seedlings grown under varied atmospheric CO2 and nitrogen levels

Climate change (elevated atmospheric CO2, and altered air temperatures, precipitation amounts and seasonal patterns) may affect ecosystem processes by altering carbon allocation in plants, and carbon flux from plants to soil. Mycorrhizal fungi, as carbon sinks, are among the first soil biota to receive carbon from plants, and thereby influence carbon release from plants to soil. One step in this carbon release is via fine root and mycorrhizal turnover. It is necessary to know the lifetime and temporal occurrence of roots and mycorrhizae to determine the capacity of the soil ecosystem to sequester carbon assimilated aboveground. In this study, ponderosa pine (Pinus ponderosa Laws) seedlings were grown under three levels of atmospheric CO2 (ambient, 525 and 700 mol CO2 mol-1) and three levels of annual nitrogen additions (0,100 and 200 kg N ha-1) in open-top chambers. At a two-month frequency during 18 months, we observed ectomycorrhizal root tips observed using minirhizotron tubes and camera. The numbers of new mycorrhizal root tips, the numbers of tips that disappeared between two consecutive recording events, and the standing crop of tips at each event were determined. There were more mycorrhizal tips of all three types seen during the summer compared with other times of the year. When only the standing crop of mycorrhizal tips was considered, effects of the CO2 and N addition treatments on carbon allocation to mycorrhizal tips was weakly evident. However, when the three types of tips were considered collectively, tips numbers flux of carbon through mycorrhizae was greatest in the: (1) high CO2 treatment compared with the other CO2 treatments, and (2) intermediate N addition treatment compared with the other N addition treatments. A survival analysis on the entire 18 month cohort of tips was done to calculate the median lifetime of the mycorrhizal root tips. Average median lifetime of the mycorrhizal tips was 139 days and was not affected by nitrogen and CO2 treatments.     

Symplasmic connections between sieve element and companion cell in the stem phloem ofVicia faba L. have a molecular exclusion limit of at least 10 kDa

High-molecular-weight fluorochromes were intracellularly injected into a sieve element of the fascicular stem phloem ofVicia faba L., using a modified membrane-potential-recording pressure probe. After stabilization of the membrane potential following microelectrode impalement, either LYCH (Lucifer Yellow CH), 4.4-kDa FITC-dextran (fluoresceinisothiocyanate-dextran) conjugate, or 3-kDa, 10-kDa or 40-kDa LYCH-dextran conjugate was microinjected into the sieve element. Longitudinal fluorochrome movement across the sieve plates and lateral displacement to the companion cells was detected with all the probes except the 40-kDa conjugate. This indicates that the molecular exclusion limit of the pore/plasmodesma units between a sieve element and a companion cell in the fascicular stem phloem ofVicia faba lies between 10 kDa and 40 kDa.Abbreviations FITC fluoresceinisothiocyanate - LYCH Lucifer Yellow CH - MEL molecular exclusion limit - PPU pore/plasmodesma unit - SE/CC-complex sieve element/companion cell complex     

七种白蚁消化道解剖形态的比较研究

本文对采自浙江省的7种白蚁（东方原白蚁、黄肢散白蚁、黑胸散白蚁、肖若散白蚁、家白蚁、杨之江近歪白蚁和和大鼻象白蚁）的消化道形态进行了解剖比较研究。并初步探讨了白蚁消化道形态在白蚁系统发育和进化中的意义。     

Microtubules are involved in maintaining the cellular polarity in pollen tubes ofNicotiana sylvestris

Summary The polarity of a growing pollen tube is clearly reflected by a distinct zonation of the cytoplasmic content. The vegetative nucleus and the generative cell (GC) are located in the tip region of the tube, and the basal cytoplasmic portion is highly vacuolated. Using pollen tubes ofNicotiana sylvestris Spegazz. & Comes grown in vitro, we examined the effects of varying concentrations of the microtubule inhibitors colchicine and propham. The depolymerization of the cortical microtubules by 25 M colchicine led to a disorganization of the cytoplasm, i.e., vacuolization of the tip region, and to a deranged position of both the vegetative nucleus and the generative cell. The same concentration of colchicine inhibited tube growth by 10–20% of the control. Mitosis of the GC was not affected. Only from concentrations of 200 M the configuration of the GC's microtubules was altered and an inhibition of mitosis was observed. At this concentration the disorganization of the cytoplasm was always reversible, but neither inhibition of mitosis nor derangement of the nuclear positioning was. At 1,800 M colchicine, pollen tube growth was inhibited by 50% of the control. Using propham, the same three steps of action were observed, although propham proved to be about a hundred times more effective than colchicine. We conclude that the cortical microtubules of the pollen tube are involved in maintaining cellular polarity, probably as a part of a heterogeneous cytoskeletal network including also microfilaments and membranous elements. Nuclear positioning seems to be dependent on both, the tube's cortical and the GC's microtubules. A possible involvement of the extracellular matrix in maintaining intracytoplasmic polarity is suggested.Abbreviations DAPI 4,6-diamidino-2-phenylindole - EGTA ethyleneglycol-bis-(aminoethyl ether) tetraacetic acid - GC generative cell - MF microfilament - MT microtubule - PEM-buffer 50 mM PIPES, 1 mM EGTA, 2 mM MgSO₄, pH 6.9 - PBS phosphate buffered saline - PIPES piperazine-bis-ethanesulphonic acid - PTG-test pollen tube growth test - VN vegetative nucleus Dedicated to Professor Peter Sitte on the occasion of his 65th birthday     

Characterization of a pollen-expressed gene encoding a putative pectin esterase ofPetunia inflata

From a pollen tube cDNA library ofPetunia inflata, we isolated cDNA clones encoding a protein, PPE1, which exhibits sequence similarity with plant, bacterial, and fungal pectin esterases. Genomic clones containing thePPE1 gene were isolated using cDNA for PPE1 as a probe, and comparison of the cDNA and genomic sequences revealed the presence of a single intron in thePPE1 gene. During pollen development,PPE1 mRNA was first detected in anthers containing uninucleate microspores; it reached the highest level in mature pollen and persisted at a high level inin vitro germinated pollen tubes. The observed expression pattern of thePPE1 gene suggests that its product may play a role in pollen germination and/or tube growth.