摘要:

ABSTRACTThe uptake of 814C‐labelled dissolved carboxylic acids byAnkistrodesmus falcatus(Corda) Ralfs,Chlamydomonas segnisEttl andChlorellasp. was measured. The acids were acetic, citric, fumaric, glycollic, lactic, malic, pyruvic and succinic acids. For some substrates uptake was active, but for others it was apparently passive. The respiratory loss of substrates ranged from 5.0 to 95.0% of the total amount of C assimilated. The potential ability of these organisms to compete with bacterial populations for such substrates in natural waters was examined. In terms of the kinetics of assimilation it appeared thatA. falcatusmight compete successfully for glycollate, lactate, pyruvate and succinate; C. segnisfor glycollate and lactate andChlorellasp. for lactate, malate and possibly glycollate. Calculated replacement times of the algae on the 8 substrates did, however, indicate that although they might compete successfully for some substrates they were generally unable to grow upon them at the concentrations provide

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02877.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02421.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02878.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTThe ultrastructure of 4 species of the calcareous, siphonaceous algaHalimeda (H. cylindraceaDecaisne,H. discoideaDecaisne,H. macrolobaDecaisne andH. tuna(Ellis&Solander) Lamour) has been studied, and the observed changes during growth and development are related to changes in the degree of calcification. A distinct gradient in the types and quantities of cell organelles exists in a growing apical filament. As these filaments grow, branch, and eventually develop into a mature segment, changes in the organization of organelles such as mitochondria and chloroplasts are observed. Calcification begins when the chloroplasts reach structural maturity and when the peripheral utricles adhere (fuse). This adhesion of the peripheral utricles isolates the intercellular space (ICS) in which calcification occurs from the external seawater. Calcification begins in the outermost (pilose) cell wall layer of the walls facing into the ICS. The cell walls at the thallus exterior undergo extensive changes after utricular fusion; the pilose layer is lost, the cuticles of adjacent utricles fuse forming a ridge at their junction, and multiple cuticles are formed.The aragonite (CaCO3) crystals which are initially precipitated within the pilose wall layer, rapidly increase in size and number, eventually filling much of the ICS. Only the initial nucleation of aragonite is associated with the pilose wall layer, the later precipitation of aragonite is totally independent of the pilose layer. In older segments secondary deposition of CaCO3also occurs around existing aragonite needles.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02879.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTThe envelope and stalk ofColacium mucronatumBourr.&Chad, were examined in living cells with light microscopy and in fixed preparations with scanning electron microscopy using critically point dried (CPD) and freeze dried (FD) preparations. The envelope of palmelloid cells is formed over the entire cell surface by many individual strands attached at right angles to areas of articulation of the pellicular strips. Strands were observed to anastomose on the posterior tip of otherwise naked cells. Stalks of living cells in India ink preparations had an optically dark inner core with a lighter outer sheath. In FD stalks a definite inner core was not evident, whereas CPD stalks had an outer surface composed of thick strands which may be the collapsed and aggregated strands of the FD stalks. In both there was also an amorphous matrix. The stalk forms from the aggregation of many strands from the anterior cell tip back to a point encompassing the cell surface anterior to a cross section of the tip 9 μm diam. The outer surface of the stalk comes from the pellicular surface joining that area and the core from the cell tip in the area of the canal opening. Any possible participation of the inner canal surface in stalk formation could not be determined because of the great density of the mucilage at the cell‐tip/stalk juncti

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02880.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTRed blooms of snow algae consisting almost exclusively of large spherical red cells ofChlamydomonas nivalis(Bauer) Wille are widespread during the summer in the Beartooth Mountains in Montana and Wyoming. Field studies designed to examine the effects of temperature, light, and water potential on algal activity were performed with natural populations using photosynthetic14C‐HCO3‐ or14CO2incorporation as a measure of activity. The algae photo‐synthesized optimally at 5.4 × 104lx, but were not inhibited by increased light intensity up to 8.6 × 104lx, the maximum observed in the field. Photosynthesis was sensitive to a reduction in water potential, and since low water potentials develop in snow at temperatures below 0 C, it is unlikely that significant algal activity occurs at the sub‐0 temperatures which occur throughout winter. Photosynthesis was much lower following melting of the snow, but this was probably due to decreased diffusion of CO2. The optimal temperatures varied considerably among the different algal populations. Most samples photo‐synthesized optimally at 10 or 20 C but retained substantial activity at temperatures as low as 0 or ‐3 C. Exceptional samples photosynthesized optimally at 0 or ‐3 C. It is proposed that the varied temperature responses reflect the presence of different temperature strains. Taken together, the data suggest that development of the snow algae can occur only during th

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02881.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTPart of the cytoplasm, which always contains the plastid, of seta‐bearing cells ofColeochaete scutataBréb. rotates clockwise about the base of the seta. Many golgi bodies, vesicles and much endoplasmic reticulum occupy the bridges between the rotating central core of cytoplasm and the stationary peripheral layer of these cells. The setae, which grow from their base, are devoid of organelles other than vesicles and elongate mitochondria. At irregular intervals along the thin seta wall are annular thickenings containing callose. Microtubules which encircle the base of the seta disappear on treatment with colchicine. This drug had no effect on the speed of rotational streaming or the growth rate of existing hairs but did inhibit the development of new setae. Cytochalasin B slowed, but did not stop, streaming after 3 h exposure. However caffeine, but not EDTA, EGTA or the Ca ionophore A23187, reversibly inhibited cyclosis. The mechanism of cytoplasmic rotation is discussed in the light of these drug treatments and the presence of actin in the al

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02882.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTExtracts of 28 species of marine macroscopic algae collected from various coastal habitats of northern California were examined for antiviral activity against a broad spectrum of mammalian viruses. Ten members of Rhodophyta contained substance(s) which caused greater than a 2 log reduction in the infectivity of herpes simplex virus types 1 and 2. In addition, anti‐Coxsackie Bsvirus activity was detected in extracts ofConstantinea simplexSetchell. The physical and chemical properties of the substance in extracts ofFarlowia mollis(Harvey and Bailey) Farlow and Setchell andC. simplexindicated the active agent was a structural polysaccharid

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02883.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTA c‐type, carbon monoxide‐binding cytochrome was isolated and studied from an endophyticNostocsp. Enzymatic transfer of electrons from NADPH to this cytochrome was demonstrated in cell‐free preparations under dark, anaerobic conditions, probably mediated by NADPH‐cytochrome reductase or ferredoxin‐NADP reductase present in the extracts. This cytochrome, with an α‐peak at 548 nm, had physicochemical properties similar to the low potential c‐type cytochrome, cytochrome c549, previously described by other workers fromAnacystis nidulans.The participation of such c‐cytochromes in dark electron transport, possibly respiratory, of bluegreen algae is st

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02884.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTConcentrations of hot‐water extractable phosphorus from most samples ofCladophora glomerata(L.) Kütz. were relatively high (0.06–0.68%) and correlated closely with total dissolved P in ambient Lake Michigan water.Cladophorawas able to hydrolyze polyphosphates by enzymes found in intracellular, extracellular and cell wall fractions. The intracellular phosphatase activity is pH dependent with the optimal hydrolysis rate at pH 7.8. Secretion of phosphatases is affected by pH, with maximum rate at 7, but affected little by light intensity. Magnesium is the most effective metallic cofactor required for maximal rates of intracellular phosphatase activi

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1977.tb02885.x

出版商:Blackwell Science Inc    

年代:1977

数据来源: WILEY