ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1985.tb04544.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1985.tb04545.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTCell division and semicell expansion in the filamentous desmidBambusina brebissoniiKütz. were investigated using transmission and scanning electron microscopy. Interphase cells are typical of desmids, containing a full complement of organelles and a cell wall penetrated by complex pores, but the cells lack a well‐defined median constriction. Cell division involves an open spindle and the centripetal growth of a primary septum formed by the fusion of small, dark‐staining vesicles probably derived from dictyosomes. Telophase nuclei are separated by a system of interzonal microtubules and numerous large, lighter‐staining vesicles also derived from the dictyosomes. Following cell division, an elaborate replicate cross wall is formed which consists of both primary and secondary wall layers. During semicell expansion, a portion of the primary wall splits apart as the new semicells evaginate and expand to their full size. The primary wall stops splitting at a thick ring of secondary wall material leaving the cells united by the remaining common layer of primary wall. When semicell expansion is completed, the primary wall is not shed from the lateral walls of the new semicells, and pores through both primary and secondary wall layers begin to produce sheath material. However, pores in the end walls of cells do not function unless the filament is broken. The intact primary wall between cells and the absence of sheath production between cells comprise the mechanism serving to hold the cells ofBambusina brebissoniitogether in long fil

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00016.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTCell division in most eukaryotic algae grown on alternating periods of light and dark (LD) is synchronized or phased so that cell division occurs only during a restricted portion of the LD cycle. However, the phase angle of the cell division gate, the time of division relative to the beginning of the light period, is known to be affected by growth conditions such as nutrient status and temperature. In this study, it is shown that the phase angle of cell division in a diatom,Cylindrotheca fusiformisReimann and Lewin, is affected by the N‐limited growth rate; cell division occurred later in the dark period (12:12 h LD cycle) when the growth rate was infradian (D = 0.42 d−1) than when it was ultradian (D = 1.0 d−1). Nitrogen‐pulses did not affect the phase angle of the division gate, but could shift the time of peak cell division activity within the division gate. The effects, if any, of N‐pulses were dependent upon the growth rate and the time of day that the pulses were administered. These responses indicate that the timing of cell division in this diatom is not determined solely by the zeitgeber from the LD cycle, but rather that a LD cycle control mechanism and a N‐mediated control mechanism are both involved and are somewhat interdependent. In addition, an increase in protein was observed immediately after administering a N‐pulse toC. fusiformisin the ultradian growth mode indicating that the accumulation of protein can be uncoupled from the cell d

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00025.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1985.tb04546.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTRadioactive bicarbonate was pulse fed to bladesof Macrocystis pyrifera(L.) C. A. Ag. and the movement of the11C‐labelled photoassimilates was monitored in vivo using an externally mounted array of Geiger‐Müller detectors. Results of experiments conducted in August 1982 and February 1983 showed kinetic transport profiles composed of short pulses of11C (periods of two to three minutes and six to eight minutes) and a mass flow component travelling with a speed of 6–22 cm · h−1. The pulse‐like movement of11C‐photoassimilates, revealed for the first time in a kelp, may be driven by an energy‐assisted transport mechanism. Light microscopy revealed a putative symplastic transport pathway from the photo synthetic meristoderm to the medullary sieve cells in theM. pyriferablade. Of particular importance were the connections between the inner cortical cells and thin‐walled medullary sieve cells. Electron microscopy showed sieve plate pore diameters ranging between 35–60 nm in the cortex and ca. 40 nm in the end walls of the thin

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00035.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTLaboratory studies have indicated that Na+, K+(together with Cl−the presumed counter‐ion to these cations), NO3−and mannitol represent the major cellular osmotica inLaminaria digitata(Huds.) Lamour. The cellular content of NO3−(together with a fraction of the K+pool which acts as the counter‐ion to NO3−) was found to be inversely proportional to that of mannitol, suggesting thatL. digitatamaintains a constant turgor by means of an isotonic substitution between these compounds. An analysis of the seasonal changes in solute content in an Arbroath (Scotland) population ofL. digitataconfirmed this hypothesis and indicated that the total pool of stored photosynthate was partitioned between the interconvertible carbohydrates mannitol and laminaran (which has a much lower osmotic potential than mannitol) depending on the size of the cellular p

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00041.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTThe structural organization of DNA in the plastids of two anomalously pigmented dinoflagellates,Glenodinium foliaceumStein andGyrodinium aureolumHulburt, was determined using the DNA‐specific fluorochrome DAPI and correlated with TEM observations. The plastids ofG. foliaceumwere found to possess both a peripheral DNA ring and isolated point nucleoids. This arrangement was shown to be similar to that of the diatomAsterionella formosaHass. and may be characteristic of the Bacillariophyceae.G. aureolumexhibited a novel distribution of plastid. DNA as one or two beaded bands, whereas the plastids of the similarly pigmented haptophyte,Emiliania huxleyi(Lohm.) Hay&Mohler, possessed scattered point nucleoids. These findings support the idea thatG. foliaceumharbours an endosymbiotic diatom, but suggest that the plastids ofG. aureolumandE. huxleyiare unrelated. The use of plastid DNA configuration as a phylogenetic marker is considere

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00050.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTCystodinium batavienseKlebs is the first dinoflagellate observed to exhibit specialized zoospore behavior which results in colonization of the epineuston. The zoospore: (1) is strongly phototactic; (2) changes shape rapidly upon release; (3) possesses at least two types of swimming behavior, including a “stop mechanism”; and, (4) sheds its theca as the new cell wall asymmetrically elongates into the immobile vegetative stage. These features working in concert facilitate the entrance ofCystodiniuminto the epineuston. Detailed observations of zoospore morphology and analysis of its behavior are used as new characters to further delimit C.bataviense.Since vegetative morphology has proven unsatisfactory in circumscribing otherCystodiniumspecies, the study of variation in zoospore characters will help to clarify taxonomic units within the ge

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00056.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY

摘要:

ABSTRACTMotileSymbiodinium microadriaticum(Freudenthal 1962) were attracted to a variety of nitrogen‐containing compounds, including ammonium, nitrate, urea and some amino acids. No chemosensory response to phosphate, sulphate, vitamins, trace metals or sugars was evident. Motile algae responded to concentrations of ammonium, nitrate, and urea at least as low as 10−6M. High concentrations (≥ 10−2M) of ammonium appeared to inhibit attraction of motile algae. Calculations using ammonium release rates from various aposymbiotic hosts suggest that motileS. microadriaticumcan respond to released ammonium ca. 1 cm from the source.Cultured algae were not attracted to combined nitrogen cues for at least 2 days after inoculation into seawater with dissolved combined low nitrogen. Algae freshly isolated from starved animals were normally motile the day following isolation and attracted to ammonium and nitrate when maintained in seawater containing<1 μM ammonium and nitrate. The algae lost their ability to orient to nitrogen attractants the day after incubation into culture medium containing high levels of ammonium and nitrate. These results suggest that chemosensory behavior is suppressed when nutrients are present in the ambient medium or are stored by the alga.There were few differences in chemosensory abilities in different strains ofS. microadriaticumto the attractants assayed, suggesting that selection for a particular strain by a host species may not be due to differential chemosensory ability or cues. However, the absence of chemical attraction of motileS. microadriaticumto infected hosts may act to preserve strain selection occurring at other steps in the infection process of aposymbiot

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1985.00062.x

出版商:Blackwell Science Inc    

年代:1985

数据来源: WILEY