摘要:

SUMMARYCapitular filaments ofPenicillus capitatuscontain a large central vacuole. The parietal cytoplasm is densely packed, devoid of chloroplasts in the growing tip, and becomes convoluted and sponge‐like as extensions of the vacuole penetrate the cytoplasm in mature portions of the filament. Structure of organelles and their distribution in the filament are described. The vacuole contains a variety of inclusions, such as membranous configurations, spherical bodies, electron dense bodies, and calcium oxalate monohydrate crystals, each of the latter surrounded by a chamber associated with microtubules. Endophytic bacteria are present throughout the vacuole and occasionally in the tip cytoplasm. Some vacuolar components ofP. pyriformisare described for compariso

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02688.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe filamentous green algaKlebsormidium flaccidumwill produce zoospores when cultured on a diurnal regime of 8‐hr light and 16‐hr dark. Zoosporogenesis is inhibited by interruption of the dark period with light of sufficient intensity and duration. The relationship between intensity and maximum time of interruption before total inhibition of zoosporogenesis is nonlin

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02689.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe insecticide Zectran decreased both respiration and photosynthesis inOscillatoria terebriformisandSynechococcus lividusat concentrations between 0.5 and 12.5 ppm, whereasNavicula pelliculosaandScenedesmus quadricaudawere, relatively unaffected by these, same concentrations in the short‐term, manometric experiments. In long‐term growth experiments all 4 species exhibited a toxicity threshold between 1 and 10 ppm Zect

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02690.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe ultrastructure of carposporogenesis forErythrocystis saccatais described. The fusion and gonimoblast cells contain few organelles, and chloroplasts are in a proplastid state, with pit plugs between gonimoblast cells dissolving early in development. Carpospore development may be separated into 3 stages, the first stage being characterized by the appearance of straight‐profiled dictyosomes, fibrous vesicles, and an increase of discoid thylakoids within the chloroplasts. During the second, stage the dictyosomes assume a curved profile and striped vesicles are formed by the endoplasmic reticulum. The third stage is initiated by the disappearance of striped vesicles and the appearance of straight‐profiled dictyosomes secreting vesicles with cores. Mature carpospores consist of many cored vesicles, fibrous vesicles, and floridean starch grains. A single wall layer surrounds each carpospore since the carposporangial wall becomes incorporated into a mucilaginous matrix surrounding the spo

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02691.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYMost vegetative cells ofBulbochaete, and all those ofOedogonium, possess an apical, circular discontinuity in the structure of their secondary wall. Rupture of the wall at this precise site permits expansion of the ring during cell division and release of the zoospore following zoosporogenesis. Certain cells ofBulbochaete(always the apical daughter cell of a division pair) lack this type of discontinuity. Instead, the apical wall is thinned out on one side, so that the cell bulges asymmetrically. In the middle of the bulge is a wall discontinuity which extends only part way around the cell. The wall will rupture here, too, for zoospore release, but if a cell having such a wall, divides, it invariably does so asymmetrically, with one pole of the spindle located in the bulge. Cytokinesis then cuts off a small, colorless daughter cell. The wall ruptures at the discontinuity, and this daughter cell emerges through the slit and differentiates into a hair.The creation of hairs in such cells commences with the deposition of a pad of primary wall lining the bulge. Golgi bodies are involved in its secretion, but not in that of a secondary wall layer which forms next in the premitotic cell and covers the primary wall. The cell becomes polarized; the nucleus migrates toward this region as the chloroplast moves aside. After the asymmetric mitosis, a curved phycoplast cuts off the hair cell nucleus and prevents the chloroplast from moving back into the future hair, whose cytoplasm soon loses much of its affinity for heavy metal stains. Following rupture of the parental wall, the phycoplast moves some distance past the limits of the newly deposited secondary wall layer and then forms a cross wall under the hair.The secondary wall of the hair isnotcontinuous with the secondary wall structure of the parental cell; the circular discontinuity that arises around the base of the bulging parental wall is then perpetuated and accentuated as the hair's secondary wall thickens. This wall weakening becomes the dislocation that will predetermine the site of the ring and consequently the direction of cell expansion in the next normal division of the cell subtending the hair. Abnormal ring formation and the creation of terminal twin hairs have also been examined. The lip of the growing hair contains a characteristic organization of membranes and other components which may be related to the organization of the hair's numerous longitudinally oriented microtubules.These results are discussed in terms of the morphology of the wall in the Oedogionales generally. The creation of the special wall morphology that leads to hair cell formation is considered to be ontogenetically related to a similar wall morphology that is involved in formation of the fertilization pore of the oogonium.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02692.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYDaily patterns of incorporation of carbon dioxide and inorganic phosphate were measured in phytoplankton from Lake George, New York, in January and February 1972. Rates of photosynthesis oscillated in phase for the entire assemblage and for individual cells of the diatomsAsterionella, Tabellaria, andFragilaria.The photosynthetic capacity was maximal in the early afternoon.Daily patterns of phosphate uptake were also rhythmic. At ambient concentrations the assemblage takes up phosphate maximally in the morning while individual cells of the large diatom take it up maximally in the evening.A kinetic analysis of phosphate uptake indicated 2 velocities of uptake for cells ofTabellariaandFragilaria:a hyperbolic function at small and an apparently linear relationship at relatively large concentrations. The large diatoms, in contrast to the total assemblage, functioned maximally at 2 separate times of the day: in the evening at ambient levels and in the morning at 0.4 μM and larger concentrations.Temporal stratification of the nutrient niche may be achieved by several uptake mechanisms in the algal cell that function at different times of the day or with a variable uptake velocity

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02693.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYMembers of the genusChordarepresent the simplest form of sporophyte in the order Laminariales. The present study deals with reproduction inChorda tomentosa, involving the initiation, growth, and structure of the sporangium and the process of zoosporogenesis. The simple tube‐like sporophyte ofChorda tomentosagrows in diameter by means of repeated anticlinal divisions in a superficial meristematic layer known as the meristoderm. The onset of reproduction is marked by the conversion of the meristoderm from contributing cells to the vegetative plant body to producing 2 new cell types: paraphyses and sporangial mother cells. At the time of initiation, sporangial mother cells are crescent shaped and possess a densely staining cytoplasm. Sporangial mother cells increase in size, become ellipsoid, decrease in staining density, and undergo meiosis. After meiosis, sporangia increase in size while their nuclei undergo successive cycles of synchronous mitotic divisions. Sporangia increase to a maximum length of 120 μ;m at which time they possess the characteristic “cap” found in all members of the order studied thus far. At this stage the protoplast of the sporangium is organized into a peripheral layer of nucleus‐chloroplast pairs and a central region of vacuoles. Cleavage furrows begin to form at the cell membrane and are met by furrows developing in the interior of the cytoplasm resulting in the division of the entire protoplast into separate units. Each unit is an individual zoospore. The biflagellate zoospores contain a nucleus, one chloroplast with eyespot, perinuclear Golgi, and several bodies of presumed storage carbohydrate. The occurrence of a small population of early developing sporangia is described. In essential details, the origin, development, and structure of sporangia inChorda tomentosaare identical to all earlier observations in the Lami

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02694.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYUsing a variety of techniques for sampling micro‐layers in freshwater environments, the frequent occurrence of significant and striking differences in algal community structure and densities relative to subsurface water is demonstrate

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02695.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYComparative study, under standard conditions of growth in a variety of media, of 2 unicellular chlorophycean algae living in soil, both of which produce spherical and saccate cells in their development, has resulted in the description of 2 new taxa,Ascochloris multinucleatagen. et sp. nov., Chlorococcaceae, Chlorococcales, andIgnatius tetrasporusgen. et sp. nov. of the Chlorosarcinaceae, Chlorosarcinales.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02696.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY

摘要:

SUMMARYThe ratio of accessory phycobiliproteins to chlorophyllais controlled by light intensity in the marine red algaGriffithsia pacifica.The greatest changes in pigment ratios are observed below 300 ft‐c; above 300 ft‐c the response approaches saturation. Ultrastructural examination of chloroplasts of plants grown at different intensities reveals that the number of phycobilisomes per unit of photosynthetic thylakoid changes in direct proportion to the pigment ratios and in inverse proportion to the light intens

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1974.tb02697.x

出版商:Blackwell Science Inc    

年代:1974

数据来源: WILEY