摘要:

SUMMARYThe ultrastructure of the reservoir region ofPhacus pleuronectesis described. Thin sections, ruthenium red staining, and shadow‐cast preparations elucidate relationships and structural details of the flagella and flagellar hairs or mastigonemes. A heretofore undescribed structure inPhacus, the multitubular structure (MTS), with associated fibrillar projections, is reported. The MTS is located in the cytoplasm at the distal region of the reservoir near the contractile vacuole. A coordinated function of the MTS and adjacent fibrillar projections is suggested. The occurrence of mastigonemes along the entire length of the emergent flagellum is suggested, in contrast to earlier reports of their presence only on that portion of the flagellum distal to the cytostome. The present investigation postulates also that the mastigonemes are bipartite, the thicker fibrous bases becoming modified distally into the classically described, mastigoneme

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02759.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe population dynamics and the sequences of statospore development and germination ofDinobryon divergensfrom a shallow subarctic lake were examined.D. divergensshowed a sharp increase in the vegetative cell population between June 19 and July 3, 1973, followed by a rapid formation of statospores from June 26 to July 3. Shortly after spore production, this species decreased sharply to an insignificant level in the phytoplankton. Statospore formation to as initialed by migration of the monad cell to the lorica mouth and proceeded by rounding up of the cytoplasm. There was then an unequal cleavage, silica wall formation around the larger portion of the cytoplasm including the nucleus and disintegration of the extracystic cytoplasm after development of the plug. The statospore was uninucleate throughout its development, and it was concluded that spore formation occurred asexually. Germination of statospores was observed in periphyton samples at depths of 20 and 80 cm on July 20–21, 1973 and in the sediments earlier the following year. During germination a cellulose chamber was produced from the pore of the statospore, followed, by cleavage of the cytoplasm within the spore and migration of approximately 4 daughter protoplasts into the cellulose chamber from which they eventually escaped. The present study proposes that chrysophycean statospores arising asexually and endogenously should be recognized as separate entities from those formed isogamously and autogamously but not necessarily endogenously. The latter statospores resulting from the sexual process have been given the term zygospor

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02760.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYMutants ofChlorella vulgarisinduced byN‐methyl‐N′‐nitro‐N‐nitrosoguanidine (NG), and, selected for the resistance to either ethionine or 6‐methylpurine, were tested for the relative rate of incorporation into protein of3H‐methionine and14C‐leucine. A highly significant, correlation between the3H‐to‐14C ratio in the protein and its methionine content was found. 6‐Methylpurine proved to be more effective than ethionine as a screening agent for high methionine strains. Screening for 6‐methylpurine resistance, followed by a second screening for the highest methionine‐to‐leucine incorporation ratio, led to isolation of the mutants with a content up to 45% higher in methionine and up to 3 times higher in cysteine wi

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02761.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYInvestigations were conducted into the effect of 3 marine bacteria,Vibrio anguillarum #19264,V. anguillarum #19109, andEscherichia coli, on the growth of 10 phytoplakters. A disc method on agar plates was used to evaluate growth responses. Growth enhancement of all algae in the presence ofV. anguillarum #19264 occurred on an enriched agar medium; the other bacteria yielded variable responses. Evidence available is consistent with the hypothesis that growth enhancement of algae is related to the release of stimulating substances through bacterial hydrolysis of the agar.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02762.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYA new species ofHymenomonas (H. coronata)has been isolated from the Texas coast, grown in axenic culture, and examined by both light and electron microscopy. Certain cultural and ultrastructural observations are presented. This alga has several haptophycean characteristics, although a definite haptonema has not been observed. Similarities to other members of the genus are evident, such us type and shape of coccoliths and pyrenoid‐chloroplast morpholog

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02763.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe intracellular concentrations of carbon, nitrogen, phosphorus and chlorophyllaof phytoplankton and zooplankton in Lake Kinneret were determined from 1969 to 1973. The ratios C:P, C:N, chlorophyll a:P, chlorophylla:N of the algae showed fluctuations which could be related to the nutrient conditions that influence the annual pattern of phytoplankton development, especially in respect to the dinoflagellate bloom ofPeridinium cinctum(OFM) Ehr. f.westii(Lemm.) Lef. Relatively high intracellurar P values at the start of the bloom indicated adequate availability of this nutrient and luxury consumption over a short period of time. Later,Peridiniumcontinued to grow despite unusually high C:P ratios (>300:1). In most years, phosphorus may have eventually limited growth, however, in 1970, the bloom censed despite comparatively high intracellular P concentrations. These observations, together with supplementary evidence from nutrient addition experiments and determinations of specific alkaline phosphatase levels, indicated that, for most of the growth phase of the bloom,Peridiniumcells were not directly limited by P. The decline of the bloom usually, but not always (e.g., in 1970), was marked by very high C:P ratios. Thus, a shortage of P may often be a contributory factor to the cessation of thePeridiniumbloom and may be limiting phytoplankton growth in the fall. Over the years 1969–73, possibly due to an overall drop in salinity, there appears to be a trend to lower levels of biologically bound phosphorus in Lake Kinneret, without a concomitant decrease in carbon biomas

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02764.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe ultrastructure of the wall layers and ornamentative features ofScenedesmus pannonicusandS. longusare described using carefully correlated freeze‐etched replicas, thin sections and scanning electron micrographs. The two species arc enclosed by different types of ornamented layers,S. pannonicusby the tightly filling, “warty” layer andS. longusby the loosely fitting, “reticulate” layer, held off the coenobium by 2 types of tubular propping spikelets and rosettes. The reticulate layer has an intricate substructure, especially when studied with freeze‐etching. Its inner and outer surfaces appear different, as is its attachment to the 2 types of spikelets. Whole cells ofS. longussubjected to acetolysis lack the cellulose wall and cytoplasm, but all other surface features survive, including the Trilaminar Sheath (TLS); this ornamentation cannot be “pectic.” The cellulose wall and ornamentation is unaffected by boiling water alone. Boiling in 6nNaOH removes the surface ornamentation, but the TLS and wall remain; the possibility that these features contain silica is discussed.The terminal spines of both species consist of closely packed spikelets enclosed within a skin of hexagonally‐packed subunits. Similar subunits are seen in the propping spikelets of S. longus, and in the rows or “combs” of laterally fused spikelets ofS. pannonicus.The warty layer ofS. pannonicusis tightly appressed to the TLS except close to where the cells are joined, where it is suspended free. It is composed of a layer of globular subunits, and small indentations form the warts. Single, evenly distributed warts characterize the freely suspended sections of the warty layer, and the layer that encloses young coenobia soon after they have been formed: in contrast, the warts are clumped over the surface of older and larger colonies. Some of the single warts form characteristic double rows, but these latter remain single even on older cells. The surface structure of the warty layer, TLS, and plasmalemma are revealed by the f

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02765.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYCell division in Scenedesmus is fairly typical of other chlorococcalean genera. The closed spindle has centrioles at polar fenestrae and apparently a series of nuclear divisions precedes cytokinesis. The phycoplast system of cytokinetic microtubules predicts the path of cleavage furrows whose mode of formation is obscure. Before and during cell division, the endoplasmic reticulum invariably accumulates granular material which later, during cytokinesis, appears to he secreted via the golgi bodies. Similar dense granular material then at accumulates outside the forming daughter cells but inside the parental wall, as the latter begins eroding away. By the end of colony formation, the cellulosic parental wall has disappeared, leaving its outer sheath and attached ornamentative features (spines, combs, reticulate or warty layer, etc.) intact as a “ghost.”The spines and combs of new colonies appear to condense out of the extracellular aggregate; their precise mode of formation is obscure. As they form, the daughter cells, having become rearranged within the parental wall, stick to one another apparently at specific sites on their outer surface. A trilaminar (sporopollenin‐containing) layer arises first in each cell at these adhesive sites and immediately afterwards, dense material aggregates between the adjacent layers to give rise to the coenobial adhesive. Plaques of the trilaminar layer later appear over the rest of the cell's surface; they grow and fuse so that eventually each cell is enclosed by one continuous Trilaminar Sheath (TLS). While the plaques are forming, another dense layer materializes around the whole coenobium. Depending on the species, this layer turns into either the warty layer, in which instance it is applied directly on to the surface of the TLS except near the coenobial adhesive, or else it becomes the reticulate layer, in which instance it remains entirely separate from the TLS, soon acquiring the complex system of propping spikelets which suspend it from the coenobial surface.When fully farmed, the daughter coenobium is tightly compressed within the parental TLS, with its spines folded lengthwise along the daughter cells. Release of the colony follows a quite explosive rupturing of the parental TLS, and immediately upon release, the daughter colony flattens out and erects its s

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02766.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe present investigation on the axial nodes of 32 taxa belonging to the generaChara, Lamprothamnium, Nitellopsis, NitellaandTolypellaconfirms previous reports that within a given taxonomic group the structure of the main axial nodal complex is highly consistent. Besides the generaNitellaandTolypellaof the tribe Nitelleae,Lamprothamniumof the tribe Chareae is the only genus in which the central cells of the main axial nodal complex subdivide. This anatomical feature of the main axial nodal complex thus clearly separates the genusLamprothamniumfrom the other genera of the tribe chareae. In 2 controversial species of the genusChara, C. hornemanniiandC. buckellii, the present study reveals that the central cells of their main axial nodal complexes do not subdivide. The transfer of these two species to the genusLamprothamniumby Daily (1) may not be appropriate.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02767.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe protein content of the filamentousCladophora glomerata(L.) Kz.,Ulothrix zonata(Web,&Mohr) Kz. andSpirogyrasp., collected from natural populations for 1 year, averaged 8.0–12.4% of the total dry weight; whereas, the corresponding levels of lipid, cellulose and ash were 11.9–16.1%, 10.0–17.8% and 14.6–24.0%, respectively. Mean values for carbohydrates, estimated by difference, ranged from 32.8 to 56.0%. The colonialScenedesmus dimorphus(Turp.) Kz. and the unicellularCosmarium laeveRab., on the other hand, contained more protein, lipid and carbohydrate (estimated by difference) averaging 13–15.0%, 22.5–25.9% and 415–46.8%, respectively, and less cellulose (7.5–9.8%) and ash (8.2–9.8%). A consistent pattern of seasonal variation in the proximate composition was not normally evident for any species, reflecting the influence of several environmental parameters on the algae.Cladophoracontained the greatest amount of phospholipid averaging; 10% by weight of total lipid with the smallest quantity (5%) inScenedesmus.The predominant phospholipid fatty acid in all species was C18:1followed by C18:2, C18:3and C16:1inCladophora, UlothrixandSpirogyra, and C16:1, C18:2and C16:0inScenedesmusandCosmarium.Oleic (C18:1) and hexadecanoic (C16:1) acids were predominant in the neutral lipids of all the algae, followed by C16:0, C18:2and C18:3. The concentration of the different fatty acids of each Species varied considerably during the year with the proportion of C16:0and C16:1, usually rising and that of C18:1failing during

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02768.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY