摘要:

SUMMARYThe marine diatomNitzschia ovalispossesses at, least 3 amino acid uptake systems, specific for transport of acidic, polybasic, and, neutral amino acids. Maximum uptake velocity (Vmax) for each, site is inversely related to the nitrogen content of the cell, and to the nitrogen available in the culture medium. Transport, of polybasic amino acids occurs throughout the course of growth in batch, culture, but theVmaxincreases dramatically as the culture ages and nitrogen/cell reaches a low value.Ksdoes not, change significantly. Acidic and neutral amino acids are taken up only by cells harvested from nitrogen‐poor culture. It appears that amino acid transport is repressed by high concentrations of nitrogen in the medium. Under natural conditions, where nitrogen concentrations are low, the contribution of amino acid uptake to the nitrogen economy ofNitzschiapopulations may be significan

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04003.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThis investigation describes the cytology of the ulotrichalean generaUlothrixandStigeoclonium.Cellular organization is similar to the degree that interphase cells of the 2 genera cannot be distinguished with certainly. InStigeoclonium, the nuclear envelope becomes disrupted at the end of prophase, and centrioles enter the nucleoplasm. At metaphase the nuclear envelope is again intact, and some of the spindle tubules appear to be contiguous with the nuclear envelope. The spindle inUlothrixis essentially open with, no attachment of spindle tubules to the nuclear envelope and with, centrioles on the spindle‐cytoplasm interface at the spindle poles. Spindle poles are blunt inStigeocloniumand pointed inUlothrix.Cytokinesis is by cell plate formation in both genera, but there is no phragmoplas

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04004.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYUltrastructure and acid phosphatase activity of aged calls ofEuglena granulataare reported. Cells are spherical, quiescent, and nonflagellated. The most conspicuous attribute of aged cells is the accumulation of cyloplasmic vacuoles and lysosome‐like structures containing heavily stained, pigmented bodies and membrane fragments. In chloroplasts, portions of whorled lamellae arc abscised and subsequently incorporated into lysosome‐like structures; osmiophilic granules increase in number. Membranes surrounding eyespot granules disappear and the granules themselves become diffuse; the usual association with microtubules is not seen in aged cells. Acid phosphatase precipitation accumulates largely at the maturing face of dictyosomes and associated vesicles; there is also activity in multivesicular and lysosome‐like vac

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04005.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYCalcification inBossiella orbigniana(Corallinaceae) is characterized by a series of features which, vary according to the age of the segment (intergeniculum). From the youngest segment at the branch tip to older, more basal segments: (1) weight and degree of mineralization increase, while rate of weight gain decreases; (2) rate and stability of calcium‐45 labeling decrease; (3) effect of light on calcium‐45 labeling rate decreases, while effect of light on stability of label increases; however, for all segments, calcium‐45 labeling is more rapid and more stable in the light than in the dark; (4) rate of calcium‐45 labeling in killed controls decreases. Comparative studies with the tropical coralline algaAmphiroayielded similar results. Characteristics of the gradients in calcification and effect of light in these coralline algae are very similar to those found, in a reef‐building coral containing symbiotic algae, and the data suggest that organic products of photosynthesis may be of general importance to calc

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04006.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYThe unicellular red algaPorphyridium aerugineumwas shown to be encapsulated by an amorphous, water‐soluble, polyanionic polysaccharide of high molecular weight. The encapsulating polysaccharide is qualitatively identical with polysaccharide found dissolved in large quantity in the culture medium. The kinetics of extracellular polysaccharide production as a function of cell age was studied. Rates of production (on a per cell basis) of both encapsulating and dissolved polysaccharides are greatest in stationary phase light‐grown cultures.Dissolved polysaccharide was quantitatively isolated by precipitation with cetyl pyridinium chloride, conversion to the calcium salt, and reprecipitation with ethanol. The procedure yields a spectrally pure product, which is composed of glucose, galactose, xylose, and 2 undetermined, sugar components, and has a sulfate content of 7.6% by weight.Electron microscopy ofPorphyridiumrevealed that Golgi vesicles transport, polymerized polysaccharides to and through the cell membrane. Similar vesicles were observed in the multicellularPseudogloiophloea, indicating that the Golgi complex plays a crucial role in the production of extracellular polysaccharides by the red algae.H14CO3‐pulse‐label experiments resulted in labeled extracellular polysaccharide in which all the constituent components contained14C. Rates of excretion of polysaccharide were found, to follow a cyclic pattern, correlated generally with the division cycle, of t

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04007.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYOn the upper surface of some specimens of the lichenLobariacf.crosa(Eschw.) Nyl. there are shrub‐like growths which have a morphology similar to that of a free‐living fruticose lichen,Polychidium umhausense(Auersw.) Henss., and contain a cyanophyte phycobiont,Nostoc.A few growths also contain scattered colonies of a chlorophyte phycobiont, in which case the lichen tissue locally assumes the foliose form characteristic of the parentLobariathallus. The differentiation of dorsiventral lichen cortices and the formation of a lax medulla and distinct algal layer are correlated with the presence of the green phycobiont. The lichen substances atranorin, gyrophoric acid, and 4‐0‐methylgyrophoric acid occur in both, the folioseL. erosathallus and the fruticose tissue. It is suggested that the fruticose structures are erumpent cephalodia which are derived from the outgrowth of internal, cephalodia and should not be considered, to be epiphytic colonies of the lichenPoly

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04008.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYPorterinema fluviatile(Porter) Waern has been found, as a microscopic filament on a culm ofSpartinafrom a tidal marsh on the Atlantic coast of Virginia. This represents the first report forPorterinemafrom a marine site in North, America.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04009.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYFive new species ofChlamydomonas, C. isabeliensis, C. pallidostigmatica, C. fottii, C. pseudomicrosphaera, andC. texensisare described. Supplementary attributes of these organisms are considered as possible taxonomic aids.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04010.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYPolyhedral viruslike particles 170 nm in diameter were found in 3‐day‐old spores of the brown algaChorda tomentosaLyngbye grown in unsterilized seawater. In sterile seawater, spores of the same species were free of these particles and cell wall development around naked settled, zoospores and subsequent spore germination proceeded, normally. Spores containing the putative virus particles did not develop cell walls or show signs of germination. Severe lysis of cell organelles always accompanied, the presence of these partic

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04011.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY

摘要:

SUMMARYDichotomosiphon tuberosusoccurs abundantly in the outflows, pools, and streams of at least 5 hard, freshwater springs of north central Florida. This tubular alga produces extensive bright green mats which harbor epiphytes, unicellular algae, ciliates, and amphipods. Within the spring, most tubes remain in the vegetative condition. After 12–15 days under certain laboratory conditions, the tubes produce highly characteristic, sex organs and akinete

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1972.tb04012.x

出版商:Blackwell Science Inc    

年代:1972

数据来源: WILEY