Gametogenesis inCoelomomyces dodgei Couch (Blastocladiales,Chytridiomycetes)

Summary The ultrastructure of gametogenesis was studied inCoelomomyces dodgei Couch (Blastocladiales, Chytridiomycetes), an obligate parasite of anopheline mosquito larvae and the copepod,Acanthocyclops vernalis. In infected copepods reared under a 16/8 hours light/dark photoperiod at 25 +2 °C., the gametophyte develops over a period of approximately seven days, and gametogenesis is triggered by the onset of the dark period during the last day of development. The initial step of gametogenesis is the elongation of the centriole to form the kinetosome, and measuring time from the onset of the final dark period (0 hours), this occurs prior to the beginning of the light period (8 hours). Subsequently, small vesicles that appear to originate from elements of the rough endoplasmic reticulum (rER) fuse at the distal end of the kinetosome forming the flagellar vesicle into which the axonemal microtubules elongate to form the flagellum (8–12 hours). Similar small vesicles apparently also derived from rER align in planes and fuse to form cleavage furrows which delineate the gamete initials (12–14 hours). As the gamete initials begin forming, the mitochondria within each initial fuse to form a single mitochondrion that associates with the lipid globules and microbodies forming the microbody-lipid globule complex (12–16 hours). The time elapsed between the formation of the flagellar vesicle to the release of mature gametes from the copepod host is about 8.5 hours. No differences were observed in the processes or timing of gametogenesis in male and female gametophytes.     

Light- and electron-microscopic studies of growth and reproduction inCutleria (Phaeophyta)

Summary Differentiation of the female gametangium inCutleria bancockii Dawson is described. Four series of mitoses result in a 16-locule structure (four tiers of four cells each). The organelles in each locule become polarized after partitioning is complete, with the mitochondria lying near the longitudinal axis of the gametangium. The nucleus and plastids are centrally located, with abundant osmiophilic material present in the cytoplasm subjacent to the gametangial surface. Both electron density and Toluidine Blue 0 staining of the material increase. Two flagella are then produced: one becomes tightly appressed to the plasmalemma near its base, and the other is free. A prominent eyespot forms in the plastid nearest the developing flagella. Golgi and endoplasmic reticulum vesicles are prolific in this region and seem to be involved with mastigoneme production and deposition on the free flagellum. Immediately beneath the plasmalemma, flagellar rootlet tubules emanate from amorphous masses near the basal bodies. Some of these tubules are associated with the eyespot. Most of the osmiophilic material is then secreted into the extracytoplasmic spaces while the gametes are rounding up. Granular-cored vesicles may be involved with pore formation and gamete release.     

Improved mating efficiency inAcetabularia acetabulum: recovery of 48–100% of the expected zygotes

Summary We have improved zygote recovery 11–1,000 fold by optimizing the physiology of gamete release and mating inAcetabularia acetabulum. Gamete release was affected by agar purity, concentration, and volume/gametangial pair. Cold pre-treatment of gametangia (14–30 d at 10°C in the dark) synchronized subsequent gamete release at 21°C in the light. Cold pre-treatment was nearly twice as effective in synchronizing subsequent gamete release when intact, gametangia-bearing caps rather than isolated gametangia were pretreated. Synchronizing gamete release doubled mating efficiency. In a wild-type laboratory strain ofA. acetabulum, there were 1,561±207 gametes/gametangium which had half-lives of 14.5 d in 0.1% seawater-agar. We recovered 48–93% of the expected numbers of zygotes from a mass mating of 8 to 1,226 gametangia and 11–128% of the expected numbers of zygotes from mating single gametangial pairs: the large range in the calculated mating efficiency may be attributable to the variation in the numbers of gametes made per gametangium. Zygote recovery from single gametangial pairs was highly dependent on the volume of mating matrix. In addition, most zygotes recovered were unattached to any other zygotes in the subsequent generation (> 95% single cells from matings of 1–500 gametangial pairs). Our improvements in mating conditions and zygote recovery (1) have facilitated cell manipulation and culture ofA. acetabulum in the laboratory; and (2) have made controlled crosses for selection and genetic analysis of mutants feasible. These advances have removed a major barrier to genetic analysis of development inAcetabularia.Abbreviations LB Luria-Bertani bacteriological broth - SE standard error of the mean - T_g agar gelling temperatures - DAPI 4,6-diamidino-2-phenylindole     

THE ULTRASTRUCTURE OF DERBESIA TENUISSIMA (DE NOTARIS) CROUAN. I. ORGANIZATION OF THE GAMETOPHYTE PROTOPLAST,GAMETANGIUM, AND GAMETANGIAL PORE1,2,3

The fine structure of vegetative and reproductive gametophytes of Derbesia tenuissima is described. Development of the gametangium and release of the gametes progress as follows: (1) In initial stages of gametangium formation, prior to 24 hr before gamete release, there is an accumulation and proliferation of nuclei, chloroplasts, and other organelles. (2) This is followed by separation of the gametangium from the rest of the plant by a gametangial membrane; segregation of organelles into gametes has begun by 12 hr before release and the process is completed by 2.5 hr before release. (3) Enzymatic wall dissolution of the pore area occurs between 2.5 and, 12 hr before normal lights-on time. (4) The release mechanism appears to be an instantaneous light-induced increase in lurgor pressure rupturing the weakened pore area, of the wall and causing a forcible expulsion of the gametes. (5) Following release, the pore is sealed by organellar debris and the gametangial membrane. Additional wall layers are presumed to be laid down internal to the plugged pore by the vegetative protoplasm which migrates into the area.     

The ultrastructure of cell wall formation and of gamma particles during encystment of Allomyces macrogynus zoospores

Structural changes during cell wall formation by populations of semisynchronously germinating zoospores were studied in the water mold Allomyces macrogynus. Fluorescence microscopy using Calcofluor white ST (which binds to -1,4-linked glycans) demonstrated that Calcofluor-specific material was deposited around most cells between 2–10 min after the induction of encystment (beginning when a wall-less zoospore retracts its flagellum and rounds up). During the first 15 min of encystment there was a progressive increase in fluorescence intensity. Ultrastructural analysis of encysting cells showed that within 2–10 min after the induction of encystment small vesicles 35–70 nm diameter were present near the spore surface, and some were in the process of fusing with the plasma membrane. The fusion of vesicles with the zoospore membrane was concomitant with the appearance of electron-opaque fibrillar material outside the plasma membrane. Vesicles similar to those near the spore surface were found within the gamma () particles of encysting cells. These particles had a crystalline inclusion within the electron-opaque matrix. During the period of initial cyst cell wall formation numerous vesicles appeared to arise at the crystal-matrix interface. Approximately 15–20 min was required for the cell wall to be formed. We suggest that the initial response of the zoospore to induction of encystment is the formation of a cell wall mediated by the fusion of cytoplasmic vesicles with the plasma membrane.Non-Standard Abbreviations GlcNac N-Acetylglucosamine - DS sterile dilute salts solution - PYG peptone-yeast extract-glucose broth     

The endomembrane system and mechanism of membrane flow in the green alga,Gloeomonas kupfferi (Volvocales,Chlorophyta) I. An ultrastructural analysis

Summary The endomembrane system of the chlamydomonad flagellate,Gloeomonas kupfferi (Chlorophyta), is complex. It consists of a proliferating ER network, a perinuclear complex of 14–18 dictyosomes and 8–12 vacuoles and an anterior contractile vacuole complex. The ER network extends from the nuclear envelope outwards, ensheafhs a dictyosome, extends out through a lobe of the chloroplast and terminates in the thin zone of peripheral cytoplasm between the chloroplast and plasmamembrane. The individual dictyosome is polar with distinct cis- and trans-faces. The cis-face is closely associated with transition vesicles emerging from the adjacent ER. Large vesicles emerge from peripheral swellings of terminal cisternae. The dictyosome-associated ER is connected to the peripheral vacuolar system. During cell division and cytokinesis, changes in the endomembrane system occur. Dictyosomes divide and quickly separate to form perinuclear complexes around the daughter nuclei. Each dictyosome undergoes morphological changes during this wall precursor-producing stage. ER lines the furrow zone and is closely associated with phycoplast microtubules. A discussion of the endomembrane system in membrane flow mechanics is provided.Abbreviations ER endoplasmic reticulum - OsFeCN Osmium ferricyanide     

The role of microtubules during the cytokinetic events of cell wall ontogenesis and papilla development inCarteria crucifera

Summary An ultrastructural study of cytokinesis, cell wall ontogenesis, and papilla development/form inCarteria crucifera Korsh. andChloromonas rosae Ettl was undertaken. After typical phycoplast-mediated cytokinesis, wall ontogenesis begins at the level of Golgi apparatus activation and secretion to the outside of the daughter cells of fibrillar wall precursors which self assemble into the typical chlamydomonad wall (sensuRoberts 1974). As wall ontogenesis approaches the flagellar region of the cell, several precisely timed events occur: flagellar apparatus formation, flagellar emergence, protoplasmic extension in the future papilla area underlined by series of parallel aligned microtubules, wall formation (at least the W₂–W₆ layers), retraction of the protoplasmic extension and loss of underlying microtubules, and final wall modification (gap filling by W₁ material) to yield the characteristic wall papilla. The transient cytoplasmic extensions mimic the shape of the future wall papilla and are maintained, at least inCarteria, by underlying microtubules. Structural and developmental properties of the papilla are characterized and phylogenetic implications are discussed.This research was supported by National Science Foundation Grant DEB 78-0554.     

Induction of abnormal male gametes and androgenesis in the aquatic PhycomyceteAllomyces

Summary Induction of cleavage of the cytoplasm in the gametangium of a predominantly male strain of the aquatic PhycomyceteAllomyces under conditions of oxygen starvation, in the presence of dilute lactic acid, or dilute phosphate buffer, pH 7.0, resulted in multinucleate-multi-flagellate gametes. Under certain conditions the frequency for such abnormal gametes approached 70%. Phosphate buffer pH 7.0, at a concentration of 5 × 10^–3-1×10^–2 M and an incubation time of 90 minutes was found to be most effective in inducing multi-flagellate-multinucleate gametes. Nuclear fusion and multiple nuclear fusions were observed in these abnormal gametes as they developed into sporophytic thalli on dilute nutrient agar (YpSS/10). Multinuclear gamete development and nuclear fusion was analysed by electron microscopy. The reported observations reveal the occurrence of androgenesis from multinuclear male gametes inAllomyces.     

MALE GAMETES OF ATRACTOMORPHA ECHINATA HOFFMAN (CHLOROPHYCEAE)1

Many naked gametes are produced in each fusiform, male gametangium of Atractomorpha echinata Hoffman and are liberated through irregularly shaped pores in the gametangial wall. They are typically biflagellate, pyriform or fusiform in shape, 6-11 μm long, and only a few micrometers wide. A mature male gamete is characterized by: (i) a nucleus with condensed chromatin and no nucleoli, (ii) a reduced, starch filled chloroplast occupying a posterior position, and (iii) a cup shaped eyespot consisting of a single layer of plastoglobuli. The flagellar apparatus includes two types of flagellar roots alternating in a cruciate pattern. One type consists of two microtubules, while the other consists of microtubules of varying number, usually eight or nine, but rarely as many as eleven. The paired basal bodies are connected anteriorly by a broad, striated distal fiber; there is no dense apical cap as reported in Sphaeroplea sperm. A unique structure, consisting of three layers of small subunits (6–8 nm diameter) arranged in a paracrystalline array, is positioned beneath each basal body. Based on the structure of its male gametes, Atractomorpha clearly demonstrates affinity with the chlorophycean rather than the ulvaphycean line of evolution. Moreover, if phylogenetic affinities for the Sphaeropleaceae are to be sought among other groups of green algae, the Chlorococcales appears the most promising candidate.     

OBSERVATIONS ON THE ULTRASTRUCTURE OF THE MALI GAMETES OF BIDDULPHIA LEVIS EHR.1

The marine centric diatom Biddulphia levis produced uniflagellate fusiform male gametes completely within the parent cell frustule. These gametes lacked both a central pair of microtubules in the flagellar axoneme and chloroplasts but did contain a cone of microtubules which passed posteriorly from the base of the kinetosome along the nuclear envelope. The gametes were released through a specialized pore in the girdle band leaving behind a cytoplasmic mass which contained chloroplasts and other cytoplasmic components. Tubules which resembled the flimmer hairs on the gamete flagellum occurred in cisternae of the cytoplasmic reticulum in the residual cytoplasm and in the nuclear envelope of the gametes. Gametogenesis in B. levis is compared with similar processes in other centric diatoms.     

Complex interspecific hybridization in barley (Hordeum vulgare L.) and the possible occurrence of apomixis

Summary Several complex hybrids were produced from the combination [(Hordeum lechleri, 6x xH. procerum, 6 x) × H. vulgare, 2 x]. Crosses with six diploid barley lines resulted in triple hybrids, most of which had a full complement of barley chromosomes (no. 1–7), but were mixoploid with respect to alien chromosomes (19–22). In one combination, chromosome no. 7 was duplicated. Meiosis in triple hybrids showed low, but variable pairing (1.3–5.5 chiasmata per cell). The syndesis probably did not include the barley chromosomes. Direct back-crosses to di- and tetraploid barley lines were unsuccessful. Chromosome doubling of the triple hybrid based on cv Pallas resulted in a plant with 2n = 53–56, which had an increased fertility. Backcrosses to one di- and one tetraploid barley line resulted in offspring. The cross made with the tetraploid line (Haisa II), produced a 28-chromosomic plant in which the male parental genome was absent. We suspect that this plant may have arisen through parthenogenetic development of a reduced female gamete. The other cross with a diploid line (9208/9) resulted in plant with 2n = 51–53. The most likely explanation for this second plant is that an unreduced gamete from the amphiploid was fertilized by a normal gamete from the backcross parent, and during early embryo development, some chromosomes were eliminated.     

An autolysin dissolves the inner cell wall layer of the algaPediastrum (Hydrodictyaceae)

Summary An autolysin produced by young colonies ofPediastrum frees them from the vesicle in which they are formed within 12 hours of release of zoospores from the parent cell. The polysaccharide vesicle is derived from the inner wall layer of the parent cell. Refrigeration delays vesicle disintegration; boiling stops it completely. A purified, lyophilized extract of the vesicle fluid added to boiled vesicled colonies removes the vesicle in 2 hours with the release of reducing sugars and polysaccharides.Biogel P2 and P10 chromatography of the products following incubation of the enzyme preparation and wall showed no more than 1% oligosaccharides; the remaining carbohydrates had a molecular weight of several thousand daltons. Analyses of isolated vesicle wall material (70–85% of the dry weight) showed mannose accounting for approximately 50% of the dry weight, with none of the other neutral sugars present (fucose, xylose, galactose and glucose) representing more than 3%. Uronic acids account for 20–25% of the wall weight, and proteins less than 2%. Pediastrum colonies are thus freed from the vesicles in which they are formed by the action of an autolysin they produce. The autolysin acts on the vesicle wall material to generate reducing sugars and cause it to disintegrate into its constituent polysaccharides.     

Developmental features of protophloem sieve elements in roots of wheat (Triticum aestivum L.)

Summary Protophloem sieve elements (PSEs) in roots of wheat (Triticum aestivum L.) are arranged in single vertical files. The number of PSEs within the files increases by symmetrical divisions, which take place after the completion of asymmetrical (formative) divisions and before the initiation of differentiation. The divisions are preceded by well defined pre-prophase bands (PPB) of microtubules, which surround the nucleus in an equatorial position. In the cytoplasmic region between the nuclear surface and the PPB, perinuclear and endoplasmic microtubules were observed. The perinuclear microtubules are considered as part of the developing spindle, while the endoplasmic ones interlink the perinuclear microtubules with the PPB. Dividing cells do not show any signs of incipient differentiation. The first and most reliable indication of a commencing differentiation is provided by the sieve-element plastids that begin to accumulate dense crystalloid inclusions in the very young PSEs. In mature PSEs plastids contain two kinds of crystalloid inclusions, dense and thin, in a translucent stroma. Depending on the plastid-inclusions criterion it was shown that: (a) the PSEs of a given root do not initiate differentiation at exactly the same stage, (b) the developmental sequence extends to a span of 7–9 actively differentiating PSEs arranged in a single vertical file, and (c) each PSE needs about 16–21 h to pass through the whole developmental sequence. In the last two differentiating PSEs of a file, mitochondria were found to be enveloped by single cisternae of ER. The association is temporary as it is lost in the first PSEs with an autolysed lumen. During differentiation, Golgi bodies were abundant and active in producing vesicles involved in cell wall development. Golgi vesicles were also found among the microtubules of the PPB, but no local thickening was observed. Golgi bodies disorganize in the last stages of autolysis and disappear in mature sieve elements.Abbreviations ER endoplasmic reticulum - MSE metaphloem sieve element - PPB pre-prophase band - PSE protophloem sieve element Dedicated to Prof. Dr. Dr. h.c. Eberhard Schnepf on the occasion of his retirement     

Wall appositions induced by ionophore A 23187, CaCl2, LaCl3, and nifedipine in characean cells

Summary The formation of wall appositions (plugs) by ionophore A 23187, CaCl₂, LaCl₃, and nifedipine was studied in mature internodal cells of characeaen algae. CaCl₂ at concentrations above 10^–2M induces thick fibrillar plugs without callose inNitella flexilis. InChara corallina andNitella flexilis ionophore A 23187 (1.25×10^–5 to 5×10^–5M) and LaCl₃ (7.5×10^–5 to 2.5×10^–4M) cause flat appositions which contain callose and have a more granular structure. Plug formation by ionophore A 23187, CaCl₂, and LaCl₃ is pH-dependent and occurs beneath the alkaline regions of the cell. Nifedipine (10^–4 to 10^–5M) induces plugs inNitella flexilis after previous injury. These callose-containing wall appositions consist of a heterogeneous granular core which is covered by a fibrillar layer. The results of this work are compared with previous studies on wound wall formation and chlortetracycline (CTC)-induced plug formation which reveal that abundant coated vesicles occur only when a thick fibrillar wall layer is formed. Neither LaCl₃ nor nifedipine inhibit the formation of CaCl₂- or CTC-plugs. The unusual effects of these substances, which normally act as Ca²⁺ antagonists and therefore should prevent and not induce plug formation, are discussed. It is suggested that La³⁺ mimicks the effects of calcium and that nifedipine binding to the Ca²⁺ channels is altered in the alkaline regions of characean internodes and allows an influx of Ca²⁺.Abbreviations AFW artificial fresh water - CTC chlortetracycline - DCMU dichlorphenyldimethylurea - DMSO dimethylsulfoxide - EGTA ethyleneglycoltetraacetic acid - MES 2-(N-morpholino) ethanesulfonic acid - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - TAPS N-tris[hydroxymethyl]methyl-3-aminopropanesulfonic acid     

Dinoflagellate cyst production in one-liter containers

Methods for the production of dinoflagellate cysts in two types of 1 L containers have been developed. Using these methods, dinoflagellate cysts can be produced in amounts large enough for shellfish grazing experiments or whenever large amounts of cysts are needed. The species used were Scrippsiella lachrymosa (B-10) and toxic Alexandrium fundyense (CB501 and GTM25). Cultures of S. lachrymosa yielded 628 ± 74 cysts mL^–1 and A. fundyense cultures yielded 350 ± 98 cysts mL^–1. Findings suggest that aspects of the boundary layer between the media and the wall of the container are important for gamete mating; especially, the slope of the container wall appears to be relevant, which offers some explanation of previous observations that the shape of the container is important in the formation of dinoflagellate resting cysts. These observations may support the theory that physical interfaces in nature facilitate dinoflagellate encystment.     

Microtubules and the flagellar apparatus in zoospores and cysts of the fungusPhytophthora cinnamomi

Summary A correlated immunofluorescence and ultrastructural study of the microtubular cytoskeleton has been made in zoospores and young cysts ofPhytophthora cinnamomi. Labelling of microtubules using antibodies directed towards tubulin has revealed new details of the arrangement of the flagellar rootlets in these cells, and of the variability that occurs from cell to cell. Most of the variation exists at the distal ends of the rootlets, and may be correlated with differences in cell shape in these regions. The rootlets have the same right and left configuration in all zoospores. The arrangement of the rootlet microtubules at the anterior end of the zoospores raises the possibility that the microtubules on the left hand side of the groove may not comprise an independent rootlet which arises at the basal bodies.The absolute configuration of the flagellar apparatus has been determined from ultrastructural observations of serial sections. In the vicinity of the basal bodies, there is little, if any, variation between individuals, and the structure of the flagellar apparatus is similar to that described for related species of fungi. Two ribbon-like coils surround the central pair of microtubules at the distal tip of the whiplash flagellum, and clusters of intramembranous particles, similar to ciliary plaques, have been found at the bases of both flagella. There are two arrays of microtubules associated with the nucleus in the zoospores. One array lies next to the outer surface of the nuclear envelope, and probably functions in the shaping and positioning of the apex of the nucleus. The nuclear pores in this region are aligned in rows alongside these microtubules. The second array is formed by kinetochore microtubules which extend into a collar-like arrangement of chromatin material around the narrow end of the (interphase) nucleus. During encystment, all flagellar rootlets are internalized when the flagella are detached at the terminal plate. The rootlets arrays are no longer recognizable 5–10 minutes after the commencement of encystment.     

The fine structure of the carapace integument of Daphnia magna straus (Crustacea branchiopoda)

Summary The structure of the two integumental layers comprising the carapace of female D. magna was examined at several points through the molt cycle. The epicuticle and procuticle are simple in organisation; pore canals are absent but intracuticular fibres are present, forming complexes with invaginations of the epidermal plasma membrane similar to such complexes described in the literature for other arthropods. The epidermis consists almost entirely of cuticle-secreting cells. Secretion of the new cuticle begins when 50–67% of the instar has elapsed by which time the epidermal cells have increased in height and their nuclei have become more rounded. However, other presumed secretory phenomena observed viz. the formation of dense core vesicles by Golgi bodies, and the occurrence of these and coated vesicles near the apical plasma membrane are not restricted to any particular period during the molt cycle. This suggests that the mechanisms of cuticle secretion do not undergo marked changes in activity as they do in decapods; presumably this relative continuity is related to the much shorter molt cycle of cladocerans.The technical assistance of G.A. Bance, and the financial support provided by the National Research Council of Canada are gratefully acknowledged     

Observations on the ultrastructure ofFrankia sp. in root nodules ofDatisca cannabina L.

Summary The fine structures of the microsymbiont inside the root nodules ofDatisca cannabina have been studied by light, by transmission- and by scanning-electron microscopy. The endophyte is prokaryotic and actinomycetal in nature. The hyphae are septate and branched, diameter 0.3–0.5 m. The tips of hyphae are swollen to form electron-dense, clubshaped to filamentous vesicles, ranging in diameter: 0.4–1.4 m. The endophyte penetrates through walls of the cortial cells. The infected zone is kidney shaped and confined to one side of the acentric stele. The orientation of infection is reversed from other actinorhizae exceptCoriaria. The hyphae are near the host cell wall and vesicles are directed towards the central vacuole. Vesicles are aseptate and no collapsing of the vesicle cell wall (void area) has been observed. Vesicle clusters structures are globular with an opening at one side of the cluster. The host cell is multinucleate or contains a lobed nucleus. Groups of mitochondria are located in between the hyphae, suggesting a strong association between the host and the endophyte for energy supply and amino acid production. The consequences of the inability to separate the mitochondria from the vesicle clusters in nodule homogenates in physiological studies have been discussed.Isolated vesicles clusters showed dehydrogenase activity, indicated by the presence of formazan crystals, after incubation with NADH and NBT. Strongest reducing activity was found within the vesicles. The possible role of filamentous vesicles in nitrogen fixation has been discussed.     

Membrane glycoproteins of Chlamydomonas eugametos flagella

The flagellar glycoproteins exposed on Chlamydomonas eugametos gametes were labeled by means of lactoperoxidase, diiodosulfanilic acid and chloramine T, and characterised in SDS-electrophoresis gels. The medium from gamete cultures contains particles (isoagglutinins) that agglutinate gametes of the opposite mating type. When crude preparations of these particles were subjected to isopycnic centrifugation in a caesium chloride gradient, two bands of particles were found. The lighter, active band consisted of membrane vesicles. The denser, inactive band consisted of cell wall material. The active band had the same glycoprotein composition as membrane vesicles artificially made from isolated flagella. Preparations of glagella were also separated on a caesium chloride cushion into pure flagella and cell wall material. The flagella, but not the cell wall material, isoagglutinated opposite gametes. Again the glycoprotein composition of pure flagella was similar to that of pure isoagglutinin vesicles. No difference was detected between the protein and glycoprotein compositions of flagella and isoagglutinins from both mating types.Abbreviations LPO lactoperoxidase - PB phosphate buffer - DISA diazotized ¹²⁵I-iodo-sulfanilic acid - SDS sodium dodecyl sulphate - CBD coomassie Brilliant Blue - PAS periodic acid Schiff     

Vischeria stellata (Eustigmatophyceae): ultrastructure of the zoospores,with special reference to the flagellar apparatus

Summary Ultrastructure of the zoospores ofVischeria stellata (R. Chodat ex Poulton) Pascher is investigated, with particular reference to the system of flagellar roots. Microtubular roots and a rhizoplast are present and a model showing their distribution is proposed. Four microtubular roots attach to the basal bodies in a system basically similar to that displayed by the heterokont algae and fungi. The rhizoplast is also similar to that of other heterokont algae. We conclude from these observations that the class Eustigmatophyceae should be placed within the division Heterokontophyta.Abbreviations C chloroplast - B basal body of the emergent flagellum - B' second basal body - E eyespot - F emergent flagellum - FS flagellar swelling - LV lamellate vesicle - M mastigonemes - MTs microtubules - N nucleus - R 1–R 4 microtubular roots - Rh rhizoplast - SB striated band - SV spiral vesicle