摘要:

SUMMARYThe halogens—chlorine, bromine and iodine—play an important, role in the biochemical processes of marine red algae. Recent studies show that various species from at least 5 orders of the Rhodophyta possess the unique ability to synthesize organic halogen‐containing compounds which are derived from seawater components. A variety of substances have been reported, with various structures from simple aliphatic halo‐ketones and brominated phenols to more sophisticated mono‐, sesqui‐ and diterpenes. While the biological functions of these compounds are not clearly understood, they appear to provide environmental advantage, probably involving predator avoidance responses and microflora

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02775.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSexual reproduction is induced in the dinoflagelatePeridinium cinctumf.ovoplanumLindemann when exponentially growing cells are inoculated into nitrogen deficient medium. Small, naked vegetative cells, produced by division of the thecate cells, then act as gametes. The zygote remains motile for 12–13 days during which time it enlarges and the theca which it forms becomes warty. Thirteen to 14 day s following plasmogamy the zygote is nonmotile, the protoplast contracts, a large red oil droplet appears, the wall thickens and becomes chitinized. This hypnozygote germinates within 7–8 weeks at 20 c producing 1 post‐zygotic cell retaining the large red oil droplet. The presence of 4 nuclei in these post‐zygotic cells may be demonstrated by staining them with acetocarmine. Two of these nuclei are smaller than the other two and probably abort. One may infer that meiosis occurs immediately prior to or at the germinartion of the hypnozygote. This post‐zygotic cell divides within 24 h into 2 daughter cells each with a promment red oil droplet. These daughter cells divide after 2–3 days into ordinary vegetative cells.Attempts to induce sexual reproduction by changes in temperature or light and by inoculation of cells into media deficient in a number of basic elements were u

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02776.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSexual males ofVolvox carteriStein f.nagariensis Iyengarsecrete a hormone which induces sexual rather than asexual development in the next generation. Male recombinants from the original strains isolated from Japan showed an increase in potency of up to 100 times that of the original male clone, with later descendants showing potencies ranging from 100 times to 1/1000 the potency of this male. Potency is defined as the extent to which the hormone produced in 1 ml of medium by one parental spheroid containing 16 male spheroids can be diluted and retain its capacity to induce sexual differentiation. This is recorded as the percent of female response in the tube of limiting dilution, asexual females of the normal female strain being used as assay inoculum in a 1 in 10 dilution series of samples of male fluid containing the sexual hormone. Investigation of the genetic basis for potency in this species included selection of high and low potency male clones and crossing with sib females or backcrossing with original female. Results of the various crosses are interpreted as multigenic system not linked with sex, with more than one genotypic class per dilution level and with more than one genotypic class per apparent phenotypic class. Possible genic interactions are described in their relevance to the biosynthesis of a glycoprotein molecule, the sexual hormone having been characterized as a glycoprotein by Starr and Jaenicke (18).

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02777.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThe ultrastructure of logarithmic‐growing cells and of resting cells in laboratory cultures ofAmphora coffaeformis(Ag.) Kütz. isolated from deep ocean water was examined using electron and light microscopy. The acid Phosphatase activity, chlorophyll a and lipid content were assessed at weekly intervals of resting cell formation during cold‐dark treatment, simulating deep ocean water. Approximately 4 wk are required to complete resting cell formation. During the first week, the cytoplasm undergoes extensive transformation and lysosomal activity is observed. Large vacules decrease in size and many small ones develop, the mitochondria become fewer and one or more massive mitochondria appear possibly by fusion of smaller ones; the cytoplasm becomes densely granular. During the second and third week, the cytoplasm continues to contract, lipid bodies begin to develop and the plastid becomes densely stained. At the fourth week, the mature resting cell is formed containing one or more massive mitochondria, a well‐formed plastid, and granular cytoplasm containing occasional lipid droplets. There is no change in frustule morphology and the cytoplasm does not produce a protective layer. The variation in chemical constituents correlates with microscopic structure of the cells. The fine structure of cells during growth resumption when exposed to light at 25 c is presented. Previous reports of viable, chlorophyll‐containing cells at great depths in the ocean may be explained by the results reported in th

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02778.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYThere is a need for simple, inexpensive methods to maintain algal clones of constant genotype over long periods of time.Pandorinazygospores survive many environmental rigors which destroy the vegetative cells. The zygospores are the preferable from for storage of the alga and remain viable for at least 15 yr. storage procedures and germination techniques are described for zygospores of 2 species. These are compared with reports in the literature concerning other algal genera. General procedures for storage and maintenance of both vegetative cells and spores are proposed.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02779.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02780.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYAt prophase inPleurastrum,extranuclear spindle microtubules develop from the region of centrioles, which lie lateral to the nucleus midway between the future sites of the metaphase spindle poles. The microtubules then move laterally to overarch the nucleus and finally become incorporated into the spindle. The centrioles do not migrate and therefore lie in the same plane as the chromosomes at metaphase. At telophase, 2, more different systems of microtubules develop from the vicinity of the centrioles—a phycoplast and extensive arrays of microtubules that ensheath the daughter nuclei. Cell division in the filamentousPleurastrumis compared to that in the green flagellate,Platymonas.The similarities between cell division in the 2 algae are interpreted as evidence: (i) that rhizoplasts (which inPlatymonasresemble myofibrils) are somehow homologous to microtubules; and, (ii) that cell division inPleurastrumdiffers from cell division in other examined filamentous chlorophycean genera because Pleurastrum has an independent evolutionary origin from a monad withPlatymonas‐like characterist

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02781.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

摘要:

SUMMARYSamples of 2 populations of the diatom,Achnanthes hauckiana Grun.,collected from Sippewissett Marsh, Massachusetts, were measured. Regression analyses of the measurements were calculated. The length/width ratio of both samples decreased almost linearly with decreasing length. The length/width ratio of the rostrate ends also decreased almost linearly with decreasing length. The number of striae per 10 μm showed a slight tendency to increase with decreasing length. Some of the specimens collected, which fit the descriptions ofA. hauckianavar.ellipticaor ver.rostrata,appear to be morphological variants of the nominate variety. The change in shape with size fits Geitler's rule of proportionally greater decrease in the apical axis than the decrease in the transapical axis.The regression lines of change in shape with size might be used as taxonomic characteristics and contain more information than the usual descriptions of limits of size and shape of a species

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02782.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02783.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

SUMMARYphosphorus‐limited chemostats were used to study the effect of degree of phosphorus deficiency on several aspects of the composition and metabolism ofAnabaena variabilisKütz. andScenedesmus quadricauda(Turp.) Bréb. The changes as a function of the dilution rate could be placed into 3 patterns. Most aspects of the composition showed it progressive change with dilution rate. The carbohydrate content generally increased while cellular P and nitrogen, protein, nucleic acid and chlorophyll contents generally decreased over the entire range of increasing deficiency studied. The changes in metabolism fell into a second pattern, showing great sensitivity to the onset of P deficiency. The ability to take up phosphate and the alkaline phosphatase activity increased most markedly with increasing deficiency at the higher dilution rates. The third pattern was confined to the, lipid content ofS. quadricauda,which increased with deficiency only at the lowest dilution ra

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1975.tb02784.x

出版商:Blackwell Science Inc    

年代:1975

数据来源: WILEY