摘要:

ABSTRACTThe three‐dimensional structure of the flagellar apparatus ofUroglena americanaCalkins(Uroglenopsis americana[Calkins] Lemmerman) was determined using serial section reconstruction. The three microtubular rootlet systems (R2, R3, and R4) follow the general pattern found in other chrysophytes. The R2rootlet originates between the basal bodies of the mastigoneme‐bearing long flagellum (F1) and the short smooth flagellum (F2) and is attached to the former by a fibrous connection. The R3rootlet system originates as a trough‐shaped band of six microtubules spanning the distance between the proximal ends of the F1and F2basal bodies. The six‐membered rootlet splits into two parts (designated R3and R3) which circle the depression from which the F2flagellum emerges in counter‐clockwise direction. These two rootlets pass beneath the F2basal body and descend into the cell alongside the chloroplast. The R4rootlet originates in fibrous material which passes diagonally over the F2basal body, forms a clockwise loop about three‐quarters of the way around the depression, and ends in the cytoplasm.In place of a typical chrysophyte R1rootlet,U. americanahas a different array of microtubules attached to the F1basal body which we have designated the descending rootlet (DR). This rootlet is a hairpin‐shaped structure lying just below the surface of the cell; its longitudinal axis is predominantly parallel to the longitudinal axis of the cell. The DR resembles the bypassing rootlet which occurs in phaeophyte zoospores. Other chrysophytes may possess rootlets which are similar to the DR fou

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00142.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe absolute configuration of the flagellar apparatus of biflagellate zoospores ofEnteromorpha flexuosa(Wulfen ex Roth.) J. Agardh ssp.pilifera(Kütz.) Bliding was determined. Viewed from the anterior of the cell, the flagellar apparatus shows 180° rotational symmetry with a counter‐clockwise absolute orientation of its components. In longitudinal sections, the posteriorly directed basal bodies form an angle of about 170°–180° to one another. A reduced striated distal fiber connects the two basal bodies. The cruciate microtubular rootlet system has a 4–2–4–2 alternation pattern. Striated microtubule‐associated components (SMACs or system I‐fibers) and rhizoplasts (or system II fibers) accompany the two‐membered rootlets. Striated bands connect the proximal sheaths with the four‐Membered rootlets. The bilobate terminal caps do not completely cover the proximal ends of the basal bodies. This is the first ultrastructural study of biflagellate zoospores in a

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00149.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTIce diatom assemblages in the Canadian Arctic are dominated by the Naviculaceae, a family which includes the genusStenoneisCleve. A taxonomic history ofS. inconspicuavar.baculus(Cleve) Cleve (including type material ofNavicula baculusCleve) is presented with morphological data including the first SEM views of the genus.Stenoneis inconspicuavar.baculuswas compared withS. obtuserostrata(Hustedt) comb. nov. (basionym:Navicula obtuserostrataHustedt). In the SEM, external, short, flattened siliceous ridges were revealed beside the proximal parts of the raphe branches and central pores. This may be a significant taxonomic feature of the genus. Valves ofS. inconspicuavar.baculusranged from 40–103 μm in length, 7–11 μm in width and had 17–20 striae in 10 μm, whereas valves ofS. obtuserostratawere shorter (27–53 μm), narrower (6–7.5 μm) and more finely striated (24–30 in 10 μm). Both taxa have a circumpolar Ar

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00156.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe sexual life cycle ofGloeodinium montanumKlebs was examined with light and scanning electron microscopy. In unialgal culturesG. montanumdivided predominantly by simple division, giving rise to two nonmotile cells. When placed in fresh medium, 2–4 biflagellated swarmers were formed from the vegetative cells. Swarmers developed directly into vegetative cells or acted as gametes. Both isogamy and anisogamy were observed.Gloeodinium montanumis homothallic. Fusion occurred in the non‐motile state producing a large aplanozygote, which germinated after approximately two months to a year or more. Zygote germination liberated four aplanospores. Budding of the zygote, resulting from unequal division of the protoplast and multiple fusion attempts also were obser

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00167.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTA systematic investigation of the genusSphaeropleawas conducted using cladistic analyses of both structural and isozyme characters for the same set of taxa. The structural data were not able to fully resolve some of the taxa while the isozyme data did produce a tree in which all nodes were supported by data. The structural characters were relatively consistent with one another, whereas the isozyme characters were much less internally consistent. Results from independent, cladistic analyses of both data sets support the concept that among thoseSphaeropleaspecies investigated,S. fragilisBuchheim et Hoffman had an early divergence. The two data sets differed primarily in that the structural data support monophyly of the genusSphaeropleaand the isozyme data do not. The greater relative consistency of the structural data suggests better support for trees inferred from its analysis. Furthermore, searches for character congruence between the two data sets revealed isozyme data which support monophyly of the genusSphaeroplea, but had been overwhelmed by conflicting isozyme characters.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00173.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe small subunit ribosomal RNA (rRNA) sequence ofGracilaria lemaneiformisBory Weber‐van Bosse was inferred from analysis of rRNA coding regions that were amplified by the polymerase chain reaction method. Comparison of theG. lemaneiformissmall subunit rRNA to homologous genes of diverse eukaryotes demonstrated that the red algal divergence was nearly simultaneous with the separation of plants, fungi, animals and many other protist lineages. This result conflicts with those of5SrRNA sequence and plastid based phytogenies which suggest that red algae represent an early divergence in the eukaryotic line of descent. Further, algae appear to be of polyphyletic origin and red algae are unrelated to higher fung

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00181.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTPhotosystem II light‐harvesting complexes were isolated from a number of ulvophycean algae. Some of these light‐harvesting complexes displayed unusual features, most notably a high apparent molecular weight (ca. 58,000) when isolated by lithium doderyl sulfate polyarrylamide gel electrophoresis. Other ulvophycean light‐harvesting complexes had a low‐molecular weight (ca. 30,000). The distribution of the high‐molecular weight complex was limited to certain members of the Caulerpales andBlastophysa rhizopus(Siphanocladales). Within the Caulerpales, there were also spectral differences between the high‐molecular weight and low‐molecular weight light‐harvesting complex types. The differences in light‐harvesting complexes in the Ulvophyceae suggest that there are two lines of evolution in the Caulerpales and thatBlastophysamay be an intermediate between the Siphon‐ocladales

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00186.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTHomozygousmt−/mt−diploid clones of theClosterium ehrenbergiiMenegh. ex Ralfs species complex were obtained by hypertonic treatment from minus vegetative cells, and mating type segregation ratios in the F1progeny of “triploid” zygospores between wild typemt+haploid andmt−/mt−homozygous diploui were analyzed. The ratio of plus to minus individuals was 1:4.8, and the ratio of the pairs of opposite mating types to those of minus mating type was 1:2.1. The results clearly show thatmt−isdominant tomt+and that the mating type inheritance in these zygospores follows the triploid‐like pattern. The validity of our assumption that the two mating types are determined by one genetic factor(mt−allele dominant) was confirmed in B1progeny analyses as well. The results suggest that this sex determining mechanism is working effectively in theC. ehrenbergiispecies complex, in which several biological species have evolved through

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00195.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTDCMU–enhanced fluorescence and extracted chlorophyllawere simultaneously measured in Narragansett Bay, Rhode Island and the MERL (Marine Ecosystems Research Laboratory) mesocosms during the 1985 brown tide bloom. Marked differences in the relationship between these variables were observed as the phytoplankton community shifted from dominance by picoalgae to diatoms. The fluorescence to chlorophyllaratio was significantly(P<0.05) higher in the mesocosms and the bay when the brown tide species(Aureococcus anophagefferensHargraves et Sieburth) dominated the phytoplankton community compared with other taxa. Although several factors could have affected the relationship we believe the high ratios are related to the pigment composition and/or small size of the brown tide organis

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00202.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTA vegetative clone of the chlorophyte macroalgaUlva rotundataBlid. was maintained in an outdoor continuous flow system and subjected to a large decrease in irradiance.Specific growth rates based on changes in fresh (μFW) and dry weight (μDW) and surface area (μSA) were determined using precut disks over the 24 h following a post‐sunset transfer from full sunlight (100% I0) to 9% I0All three measures of growth rate were approximately equivalent for untransferred control plants at either limiting (9%) or saturating (100%)I0. Transferred disks exhibited μFWand μSAwhich were slightly lower than 100%I0controls and much higher than 9% I0controls; μDWwas nearly identical for transferred disks and 9% I0controls. Cell size was unchanged following transfer, indicating that surface area changes reflected a proportional increase in cell number. Cell division therefore continued at a high rate for one day following transfer ofU. rotundatato irradiances which are subsaturating for photosynthesis (indicated by μDw). Starch reserves were largely depleted, and the C/N ratio decreased during thi

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00206.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY