The effect of current on the distribution of diatoms settling on submerged glass slides

Glass microscope slides were submerged for two to six week periods at selected sites in a small, spring-fed stream near Lennoxville, Quebec. Slides were oriented parallel and perpendicular to the current. Qualitative and quantitative data from transects across slides show that diatoms are randomly distributed on slides perpendicular to the current but not on slides oriented parallel to the current. In the later case, most individuals first settled near the upstream or downstream edge of the slide. Non-random distribution is most pronounced on slides containing Cocconeis placentula. This species and two others, Achnanthes linearis and A. minutissima, are abundant and determine most distribution patterns found on slides. Preference of diatoms for the edges of slides appears to be affected by current. We propose a model, based upon water flow, to explain the preferential distribution of diatoms on slides oriented parallel to the current. Light appears not to affect settling patterns to a great extent in this study.     

Root contraction in hyacinth III. Orientation of cortical microtubules visualized by immunofluorescence microscopy

Summary Cortical microtubules (MTs) were visualized in root cortex cells ofHyacinthus orientalis L. using immunofluorescence techniques. Cellular MT orientation was determined adjacent to radial longitudinal and transverse walls of root tip, uncontracted, contracting, and fully contracted regions. As seen in longitudinal views, MTs formed parallel, apparently helical arrays which were oriented transversely, axially or obliquely depending upon the region. Transverse sectional views showed that MTs adjacent to transverse cell walls formed a variety of patterns which varied with developmental stage and cell location. Microtubules were oriented in crisscross or parallel arrays. The parallel arrays were oriented either parallel, perpendicular or oblique to the radius of the root. There was an apparent temporal progression in MT reorientation from outer cortical to inner cortical cell layers. A resultant progression of reoriented cell growth could account for root contraction. These findings corroborate earlier electron microscopic observations of changing MT orientation accompanying root contraction, and provide cytological evidence to test mathematical and biophysical models of the mechanics of cell expansion.Abbreviations MT microtubule - MF microfibril - MTSB microtubule stabilizing buffer - PBS phosphate buffered saline     

Changes in microfibril arrangement on the inner surface of the epidermal cell walls in the epicotyl of Vigna angularis ohwi et ohashi during cell growth

Throughout the entire period of cell growth, the microfibrils on the inner surface of the outer tangential walls of the epidermal cells of Vigna angularis epicotyls are running parallel to one another and their orientation differs from cell to cell. Although transverse, oblique and longitudinal microfibrils can be observed irrespective of cell age, the frequency distribution of microfibril orientation changes with age. In young cells, transversely oriented microfibrils predominate. In cells of medium age, which are still undergoing elongation, transverse, oblique and longitudinal microfibrils are present in quite similar frequencies. In old, non-growing cells, longitudinally oriented microfibrils are predominent. A decrease in the relative frequency of transversely oriented microfibrils with cell age was also observed in the radial epidermal walls.     

Plastid apportionment and preprophase microtubule bands in monoplastidic root meristem cells ofIsoetes andSelaginella

Summary Ultrastructural observations on monoplastidic root tip cells ofIsoetes andSelaginella demonstrate two important phenomena associated with preprophasic preparation for mitotic cell division, 1. the preprophase band and 2. precise orientation of the dividing plastid relative to the preprophase band. Both of these phenomena accurately predict the future plane of cell division. The plastid divides in a plane parallel to the spindle and each cell inherits a single plastid which caps the telophase nucleus. When succesive transverse divisions occur, the plastid migrates prior to prophase from a position near an old transverse wall to a lateral position in the cell. The plastid is oriented with its median constriction precisely intersected by the plane of the preprophase band. When a longitudinal division follows a transverse division, the plastid remains in its position adjacent to an old transverse wall where it is bisected by the plane of the longitudinally oriented preprophase band microtubules.     

The change of pattern in microfibril arrangement on the inner surface of the cell wall of Closterium acerosum during cell growth

Closterium acerosum (Schrank) Ehrenberg cells cultured on cycles of 16 h light and 8 h dark, undergo cell division synchronously in the dark period. After cell division, the symmetry of the daughter semicells is restored by controlled expansion, the time required for this restoration, 3.5–4 h, being relatively constant. The restoration of the symmetry is achieved by highly oriented surface expansion occurring along the entire length of the new semicell. During early semicell expansion, for about 2.5 h, microfibrils are deposited parallel to one another and transversely to the cell axis on the inner surface of the new wall. Wall microtubules running parallel to the transversely oriented microfibrils are observed during this period. About 2.5 h after septum formation, preceding the cessation of cell elongation, bundles of 7–11 microfibrils running in various directions begin to overlay the parallel-arranged microfibrils already deposited. In the fully elongated cells, no wall microtubules are observed.     

Kinetics of the dichroic reorientation of phytochrome during photoconversion inMougeotia

In the green algaMougeotia, the dichroic orientation of the red-absorbing form of phytochrome (P_r) is parallel of the cell surface, whereas the far-red-absorbing form (P_fr) is oriented normal to it. The time course of the change from parallel to normal was investigated by double-flash irradiation with polarized red and far-red light. The results obtained by two different methods indicate that most of the phytochrome intermediates existing in the first 5 ms after the inducing red flash are still oriented parallel to the cell surface, similar to P_r. At increasing intervals between the red and the far-red flashes, more and more phytochrome molecules turn their transition moments to the P_fr orientation. This reaction is finished after approximately 30 ms. We conclude that the change in dichroic orientation of the phytochrome molecules inMougeotia occurs during the last relaxation steps of the intermediates on the way from P_r to P_fr. It cannot be decided yet, whether the first surface-normal phytochrome species is an intermediate or P_fr itself.Abbreviations P_r red-absorbing form of phytochrome - P_fr far-red-absorbing form of phytochrome A preliminary report of this work was presented at the European Symposium on Photomorphogenesis, University of Reading, UK (Kraml et al. 1982)     

Root contraction in hyacinth IV. Orientation of cellulose microfibrils in radial longitudinal and transverse cell walls

Summary Cellulose microfibrils (MFs) were visualized on the inner surface of root cortex cell walls ofHyacinthus orientalis L. using a replica technique. Microfibril orientation was determined in radial longitudinal and transverse cell walls of the root tip, uncontracted, contracting, and fully contracted regions of the root. In longitudinal walls, the innermost MFs were ordered and parallel to one another and were oriented transversely, axially or obliquely, depending upon the developmental stage of the region. In transverse walls MFs in a single layer formed crisscross or ordered parallel arrays, depending upon the region. Parallel arrays were oriented either parallel, perpendicular, or oblique to the radius of the root. Inner walls of certain cells in the contracting region had MFs which appeared interrupted over their lengths. In general, these findings parallel earlier immunofluorescence and electron microscopic observations of changing cortical microtubule (MT) orientation accompanying root contraction. The major exception to MT-MF congruence occurred in cells of the actively contracting region. In middle and outer cell layers, MFs appeared short and partially obscured, while MTs in these cells occurred in conspicuous laterally aggregated strands parallel to one another over the length of the cells or were absent. This alteration in MF-MT parallelism may be related to the reorientation in cell growth occurring in the contractile zone or to the collapse of specific cells during the process of root contraction.Abbreviations MF microfibril - MT microtubule     

Arrangement of cortical microtubules during formation of bordered pit in the tracheids ofTaxus

Summary The arrangement of cortical microtubules during the development of the secondary wall and bordered pits in the tracheids ofTaxus was examined by immunofluorescence and electron microscopy. The cambial region of radial longitudinal sections of developing young shoots (2–3 years old) contains cells at various stages of differentiation from cambial cells to tracheids. At the early stage of formation of bordered pits, circular bands of microtubules were seen to be associated with the inner edge of the border of the developing pit. In other regions than the pit secondary wall of uniform thickness was laid down, and obliquely oriented cortical microtubules ran parallel to one another. These cortical microtubules also covered the surface of the border of the developing pit on the side facing the center of the cell. As the border of the pit developed, a circular band of MTs remained associated with the inner edge of border, suggesting that the MTs were involved in the formation of the rim of the bordered pit, extending the initial border thickening, which consisted of concentrically oriented cellulose microfibrils. After completion of the formation of the bordered pit, helical thickenings became apparent. The obliquely oriented microtubules were organized in bands parallel to one another, being superimposed on the helical thickenings. The involvement of MTs in the formation of bordered pits and helical thickening is discussed.     

A helicoidal cell wall texture in root hairs ofLimnobium stoloniferum

Summary The cell wall of root hairs ofLimnobium stoloniferum is composed of two fibrillar layers: an outer layer with a dispersed texture and an inner layer with a helicoidal texture. In stained oblique sections the helicoidal layer appears as a series of bow-shaped structures. In sections which were shadow-casted after the embedding medium was removed, the following properties of the helicoidal layer can be directly observed. (1) It is build up of superimposed lamellae. (2) Each lamella consists of parallel oriented microfibrils. (3) Going into the helicoidal layer, there is a counter-clockwise discontinuous rotation of the microfibril orientation in successive lamellae. (4) Between adjacent lamellae the average angular displacement of the microfibril orientation is about 23 degrees. The dispersed outer layer is also polylamellated, but with randomly arranged microfibrils in each lamella. Both layers are present in the lateral wall as well as in the apical wall of the root hairs. Observations indicate that in the cell wall of the tip the parallel oriented microfibrils of the outermost helicoidal lamellae become distorted towards a dispersed arrangement. The suggestion is made that the dispersed outer layer is derived from the helicoidal layer.     

Spezielle Mitochondrien in den Leydig-Zellen eines Knochenfisches,Trichogaster leeri (Bleeker)

Zusammenfassung Die Ultrastruktur der interstitiellen Zellen im Hoden von Trichogaster leeri (Anabantoidei, Teleostei) wird beschrieben. In diesen Zellen kommen kleine Mitochondrien, die nur Cristae enthalten, neben großen Mitochondrien (bis zu 3 im Durchmesser) vor, die sowohl Cristae als auch Tubuli besitzen. Die Tubuli sind in parallel verlaufenden gewellten Bündeln angeordnet und können eine regelmäßige zirkuläre Streifung ihrer Wand aufweisen. Verschiedene Differenzierungsstadien dieser Mitochondrien werden mit ähnlich strukturierten Mitochondrien verglichen, wie sie in Steroid produzierenden Zellen anderer endokriner Organe vorkommen.

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Special mitochondria in the leydig-cells of the teleost, Trichogaster leeri (Bleeker)

Summary The ultrastructure of the interstitial cells in the testis of Trichogaster leeri (Anabantoidei, Teleostei) is described. In these cells small mitochondria, containing only cristae, occur by the side of large mitochondria (up to 3 in diameter) which possess cristae as well as tubules. The tubules are oriented in parallel wavy bundles and may show a regular circular striation of their walls. Various stages of differentiation of these mitochondria are compared with mitochondria in steroid producing endocrine organs.

30. Mai 1972.     

Cell hypertrophy in stems ofPinus halepensis infested byMatsucoccus josephi

Summary Structural and ultrastructural changes occurring in the living cells of young plants ofPinus halepensis Mill. artificially infected withMatsucoccus josephi Bodenheimer et Harpaz, were studied. The study revealed that, opposite the places of attachment of the insects to the stem, groups of enlarged cells occurred in the cortex and often also in the phloem and cambial zones. In the enlarged cortical parenchyma cells there was a pronounced increase in the volume of the cytoplasm. The nuclei were large and lobed. The ER appeared in two forms, in very long cisternae arranged in parallel, and in short variously oriented tubules. The plastids were without grana, contained a tubular network and many plastoglobuli. Mitochondria and dictyosomes were relatively numerous. The function of the hypertrophic cells is discussed.     

Effects of colchicine on cell shape and on microfibril arrangement in the cell wall of Closterium acerosum

Cell morphogenesis in Closterium acerosum (Schrank) Ehrenberg was greatly influenced by colchicine. Addition of colchicine to the medium led to production of tadpole-shaped cells, by decreasing the length and increasing the thickness of the new semicells. Transversely oriented wall microtubules and microfibrils, characteristic of normally elongating semicells, were not observed in colchicine-treated semicells, randomly oriented microfibrils being present instead. About 3.5 h after septum formation, the randomly oriented microfibrils began to be overlaid by bundles of microfibrils as seen in normal semicells at the later stage of elongation. When colchicine treatment was terminated 1 h after septum formation, cell elongation was partially restored and microfibrils were deposited parallel to each other and transversely to the cell axis, indicating that the effect of colchicine on microfibril arrangement in growing semicells is reversible.     

Role of the microtubule cytoskeleton in alternating changes in cellulose-microfibril orientation in the coenocytic green alga,Chaetomorpha moniligera

The functions of the microtubule (MT) cytoskeleton in changing the orientation of microfibrils (MFs) in the cell walls of the coenocytic green alga Chaetomorpha moniligera Kjellman were investigated by electron microscopy. The cortical MT cytoskeleton in Chaetomorpha was comprised of longitudinally oriented MTs. Cellulose MFs, however, alternately changed their orientation longitudinally and transversely to form crisscross MF textures. Microtubules were parallel to longitudinally oriented MFs but never to those that were transversely oriented. The average density of MTs during the formation of longitudinally oriented MFs was 216 per 50 m of wall and that of transversely oriented MFs 170/50 m. To determine exactly the MT-density dependency of each MF orientation, changes in MF orientation were examined by changing MT density after treating and removing amiprophos-methyl (APM). Microtubules were reduced in number by a half (100/50 m) after 2 h and by 3/4 (50/50 m) after 3 h of treatment with APM (3 mM). This reduction was caused by the disappearance of alternating MTs. Microtubules retained this density (50/ 50 m) up to 6 h, and then gradually disappeared within 24 h. Microfibril orientation in the innermost cell wall was transverse after treatment with APM for 2 h but was helicoidal after 6 h. Polymerization of MTs occurred in the longitudinal direction following the removal of APM after treatment for 48 h. Microtubule density rose to about 100/50 m and 200/50 m after 6 h and 24 h, respectively. The orientation of MTs changed from helicoidal to transverse and transverse to longitudinal after 6 h and 24 h, respectively. When APM was removed prior to formation of the helicoidal texture, longitudinally oriented MFs appeared within 6 h. There is thus an alternating cycle of formation of longitudinally and transversely oriented MFs within a 12-h period. Formation of transversely oriented MFs as a result of APM treatment started in the middle of a cell as hoops which then extended in the apical and basal directions. Formation of longitudinally oriented MFs as a result of the removal of APM started from the apical end and proceeded toward the base. It follows from these results that: (1) the point of formation of longitudinally oriented MFs differs from that for transversely oriented MFs, (2) MF orientation in each case depends on a separately functioning mechanism, (3) MT density changes rhythmically to trigger a switch for crisscross orientation of MFs.Abbreviations APM amiprophos-methyl - MF microfibril - MT microtubule - TC terminal complex We thank Dr. K. Okuda for making helpful discussion and Miss. T. Matsuki for assistance with replica preparation.     

Structure and assembly of the cortical microtubule cytoskeleton in the green alga,Boodlea coacta

Summary Examination was made of the structure and assembly of the cortical microtubule (MT) cytoskeleton in the coenocytic green algaBoodlea coacta (Dickie) Murray et De Toni by immunofluorescence microscopy. Cortical MTs inBoodlea protoplasts are arranged randomly but some show a meridional arrangement within 6 h after protoplast formation. At 6–9 h such MTs become highly concentrated and parallel to each other in certain areas. At 12 h the concentration is uniformly high throughout the cell, indicating the completion of high density meridional arrangement of cortical MTs. Cortical MTs exhibiting a high density, meridional arrangement show characteristic disassembly by treatment with 10 M amiprophos-methyl (APM) or cold treatment (0 °C). Disassembly occurs by each MT unit at positions skipping 30–40 m in the transverse direction, and neighboring MTs subsequently disassemble to form MT groups. Each group becomes slender and then disappears completely within the following 24 h. The meridional arrangement of cortical MTs is disrupted by N-ethylmaleimide (NEM) accompanied by a remarkable reduction in density. The remaining MTs form groups at 30–40 m intervals from each other, as also occurs with drug or cold treatment, but disruption and density return to normal levels following removal of NEM. It appears that there are meridionally oriented channels, anchor-rich and anchor-poor, in the plasma membrane. The channels could be distributed alternately and anchors could be deposited in a cross-linking manner with cortical MTs to form a stable cortical MT-cytoskeleton. MTs comprising the cortical MT cytoskeleton could be oriented by meridionally oriented channels of anchors which are distributed following establishment of cell polarity.Abbreviations APM amiprophos-methyl - MT microtubule - MTOC microtubule organizing center - NEM N-ethylrnaleimide     

Studies on the morphology,cytology, and distribution ofLeucojum subgenusRuminia

The following is a summary of part of a lecture held on february 13th 1974 at the Pädagogische Hochschule Berlin. A more detailed publication is under preparation.The following note has been based on studies parallel to those ofDamboldt & Phitos (cf. p. 119 of this issue). Results are complementary or corroborate each other. Our understanding of the interesting relationships between MediterraneanLeucojum taxa is thus improved. This justifies the parallel publication of the two articles in one issue of this journal (Editor).     

Interaction of polynuclear aromatic hydrocarbons, 4-nitroquinoline 1-oxides, and various dyes with DNA

By using the flow dichroism method, in vitro interaction of the aromatic polynuclear hydrocarbons with calf thymus DNA was studied. A clear dichroism of the hydrocarbons which interacted with DNA was observed, showing a specific type of interaction. Hydrocarbons were classified into two groups, depending on whether the orientation is parallel or perpendicular to the direction of flow. 3,4-Benzopyrene, pyrene, and phenanthrene belong to the first group, and the second group contains 20-methylcholanthrene, tetracene, pentacene, and coronene. 4-Nitroquinoline 1-oxide (4-NQO) and its derivatives have also been found to be oriented parallel to the planes of bases of DNA, and a distinct parallel was found between the amount of binding and carcinogenicity. Base specificity of binding of 4-NQO with DNA-was studied, and purines were suggested to be active sites of interaction. Actinomycin D, several acridine dyes, and methylene blue etc. were found to be oriented parallel to the planes of DNA bases, and in the cases of acridine dyes this finding does not contradict the intercalation mechanism proposed by Lerman.     

Penetration of chemicals into the Malus leaf cuticle

The adaxial leaf cuticle of Malus pumila was examined by electron microscopy to determine possible avenues for transcuticular movement of foliarly applied chemicals. Cutin-embedded polysaccharide microfibrils originated at the outer epidermal cell wall and occasionally extended to the cuticle surface. Lamellae, ca. 4 nm wide, usually were oriented parallel to the cuticle surface. When oriented perpendicular to the surface, they extended nearly to the subjacent wall layer from the surface. Aqueous solutions of uranyl acetate, silver nitrate and phenyl mercuric acetate applied to the cuticle surface of leaf segments floated on solutions of phosphate salts or thiocarbohydrazide (TCH) reacted within the cuticle to form insoluble electron-opaque deposits indicative of their avenues of transcuticular movement. Uranyl phosphate deposits were observed only in the polysaccharide microfibrils of chloroform: methanolextracted leaves. Silver-TCH deposits were observed in the microfibrils of both extracted and nonextracted leaf cuticles. Phenyl mercuric acetate-TCH deposits were randomly dispersed throughout the extracted cuticle and not associated with the polysaccharide microfibrils.Abbreviations TCH thiocarbohydrazide - PMA phenyl mercuric acetate     

Molecular organization of bacteriochlorophyll in chlorosomes of the green photosynthetic bacteriumChloroflexus aurantiacus: Studies of fluorescence depolarization accompanied by energy transfer processes

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.     

Microtubule arrays in regeneratingMougeotia protoplasts may be oriented by electric fields

Summary Initially non-polar protoplasts of the green algaMougeotia will regenerate to re-establish their original cylindrical cell shape. The orientation of the growth axis of regenerating protoplasts held in agarose was independent of both the direction of incident white light and gravity. Protoplasts elongated parallel to applied DC electric fields of approx. 0.2 Vcm^–1 (1 mV/protoplast) and greater, with an increasing percentage oriented with increasing field strength. At the maximum field strength used (10 mV/cell), 53% of protoplasts were oriented within +- 10° of the 0/180° axis of the field. In untreated controls, the orientation of elongation was random. Protoplast survival was unaffected by field treatment. Some protoplasts (up to 37% in 10 mV/cell fields) formed outgrowths towards the cathode and occasionally towards the anode. Regenerating protoplasts in fields displayed the normal sequence of microtubule reorganization. This means that the positioning of the ordered symmetrical array of microtubules centred on two foci that appears within 3 to 4 h, and the subsequent organization of microtubules by 8 to 12 h into a band that intersects both foci and which is transverse to the axis of elongation (Galway and Hardham 1986), may be controlled by externally applied electric fields. In the region of this microtubule band, the applied field causes the plasma membrane to be stretched parallel to the field (Bryant and Wolfe 1987). We suggest that microtubules may become oriented perpendicular to the direction of field-induced membrane stretching, and that membrane stretching may be one of the orienting mechanisms for membrane-linked microtubules in elongating plant cells.Abbreviations PBS phosphate buffered saline - PMM protoplast maintenance medium - DMM dilute maintenance medium - MES 2(N-morpholino)ethanesulfonic acid - TRIS tris(hydroxymethyl)aminomethane - ANOVA analysis of variance     

Effect of maize plants on colonisation of cowpea plants by bean flower thrips,Megalurothrips sjostedti

The effect of non-host maize plants on colonisation of cowpea byMegalurothrips sjostedti (Trybom) (Thysanoptera; Thripidae) was investigated. There were no differences in population density and activity ofM. sjostedti on sole cowpea crop and mixed cowpea/maize crop during the colonisation phase (i.e. 10–30 days after emergence of the plants. However, subsequentlyM. sjostedti numbers were lower in the mixed than in the sole crop, suggesting that maize did not interfere with colonisation of cowpea crop by thrips. In a choice situation, higher numbers ofM. sjostedti oriented towards, and settled on, sole cowpea plants than on those mixed with maize. Olfactory tests indicated that fewer thrips oriented towards a cowpea/maize mixed odour source. When equal numbers of thrips were introduced into the centre of sole- and mixed-cropped cowpea plots, the thrips became randomly distributed in each plot. Fewer thrips were recovered from the mixture than from the sole crop. It is concluded that, although non-host plant odours do not reduce thrips colonisation they interfere with host plant utilisation.