ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00244.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe cryptophyte algae, or cryptomonads, comprise a small algal group with a unique photosynthetic apparatus. Both a chlorophyll a/c2light‐harvesting complex and a phycobiliprotein antenna (which can be either phycoerythrin or phycocyanin) are present, with the phycobiliprotein playing the major role in harvesting light for photosynthesis. Longstanding circumstantial evidence suggested that, in cryptophytes, the phycobiliprotein is located in the intrathylakoid space (thylakoid lumen) rather than on the outer surface of the thylakoid as part of a phycobilisome as in other algae. We used immunogold labeling to show conclusively that 1) the phycoerythrin (PE) of the cryptophyteRhodomonas lensPascher and Ruttner is located within the intrathylakoid space, 2) the PE is not exclusively bound to the thylakoid membrane but instead is distributed across the thylakoid lumen and 3) a fraction of this PE is tightly associated with the thylakoid membrane. The thylakoids are not everted to compensate for this unusual arrangement. The location of the major light‐harvesting pigment on the “wrong” side of the otherwise very normal photo‐synthetic membrane is unexpected, unique to the cryptophytes, and, remarkably, does not impair the photosynthetic abilities of this organism. A model is presented which incorporates these results ‐with previous information to give a complete structural picture of the cryptophyte light‐harvest

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00245.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTHeavily lichenizedPhysolinum monile(De Wildem.) Printz from damp limestone walls in a dimly lit cave located in Missouri was studied from fresh collections and specimens fixed in situ, and from cultures. The narrow (7‐13 μm wide thallus), profusely branched plant consisted of filaments of the algaP. monileensheathed by clear fungal cells (5‐8 in a single layer) that adhered tightly to each other and completely covered the algal cells. Cells ofP. monilefilaments were uninucleate, each containing a single massive chloroplast with numerous tightly packed thylakoids and lipid droplets and surrounded by a thin layer of cytoplasm. No plasmodesmata occurred in the cellulosic crosswalls between adjacent cells. The ensheathing fungal cells contained concentric bodies, produced haustoria that penetrated the algal cells, and developed hyphae (the tips of which formed clusters of conidia). Ensheathing fungal cells were well situated and constructed to concentrate light on the algal cells. Colonies of blue‐green algae were firmly attached to the surface of the fungal cells. The association was slow growing but frequently produced and released aplanospores from the algal cells. Aplanospores were single (not attached to each other) with smooth walls or united in groups of two or more. Structures resembling lichen soredia, composed of aplanospore‐like cells attached to one or more comdia‐like cells, commonly occurred among the lichenizedPhysolinumfilaments. The single chloroplast that occupies most of the cell's volume, the numerous, tightly packed thylakoids, and light focusing by ensheathing fungus cells may enable the organism to survive in a dimly lit environment. Because the filamentous alga reproduces only by aplanospores, we propose resurrection of the genusPhysolinum.The lichenizedPhysolinumsomewhat resembles the lichensCoenogonium moniliformeTuck. andCystocole

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00246.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe effectr of phosphate starvation and subsequent uptake on distribution and concentration of phosphate metabolic intermediates and metals were studied inHeterosigma akashiwo(Hada) Hada by31P‐NMR spectroscopy, neutron activation analysis and ESR spectroscopy. Excess orthophosphate (4.5 μM Pi, as NaH2PO4) added to a medium with P‐depletedH. akashiwocells was rapidly taken up resulting in an increase in P cell quota (qp)from 68.2 to 99.6 fmol. cell‐1in 2 h and to 156.3 fmol. cell‐1in 6 h. After three days, qpapproached about 190 fmol. cell−1. Polyphosphate (PPi) rapidly increased from 0 to 11.4 fmol· cell−1in 2 h and to 24.7 fmol·cell−1in 6 h. Diel variation of cell quota indicated that cellular Piincrease was synchronized with cellular PPidecrease and vice versa. The average chain length of PPiincreased from ca. 0 to ca. 10.2 phosphate residues in 2 h after addition of Piand one day later, from ca. 9.8 to ca. 12.5.The cell quota of Mn (qMn), and to a lesser extent Co, increased rapidly from 4.87 fg. cell−1in the P‐ starved condition to 50.48 fg·cell−12 h afer addition of Pibut decreased to 8.63 fg. Cell−1by 6 h. Concentrations of Zn, As, Hf, Cu and sometimes Al, Mg, K, and Ca changed in a manner opposite to that of Mn and Co. The excretion of these cations, which was synchronized with the uptake of Mn and Co, may be important for a charge balancing in the cells. The ESR spectra showed that the high cellular Mn observed at 2 h after P addition was Mn2+which was taken up by the cells rather than adsorbed on the cell surface. These data combined with PPidata suggested that the behavior of qMnis synchronized with the behavior of av

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00247.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe dominance ofCorallinathalli in an intertidal algal assemblage was examined by a series of algal removal experiments to test the hypothesis that other tam are competitively excluded from rock substrate. An alternate explanation, that environmental factors seasonally filter out taxa leavingCorallinaas the only alga adapted for year to year survival, was considered. Development of vegetation on patches of naturally exposed bare rock was monitored and compared with manipulated surfaces. Thalli of several species were selectively removed from exposed surfaces and intact turf;. changes in tam occupying primary substrate were recorded over more than three years. No significant differences in mean percent cover forCorallina, Lithothrix,bare rock, or algal crusts were found among treatments. Except for initial growth of colonizing species, abundances of other species dad not increase in the absence ofCorallina.Large amounts of rock remained bare or intermittently covered by transient populations of short‐lived algae. Data from single quad‐rats, where individual clumps ofLithothrixwere followed from month to month, indicated that the continued presence of this co‐occurring and often abundant species depended on turnover of short‐lived thalli rather than persistence of the same clumps. No interactions were found among the several categories of species that appeared after rock substrate was cleared. Most species were the same ones that grew, epiphytically in intact turf at the same time. In control quadratsCorallinamaintained 59‐95% cover while slowly increasing on surfaces earlier exposed. I predict thatCorallinaspecies will regain their dominance in the absence of competitors for primary substrate if the slowly spreading basal crusts remain undisturbed. Morphological and life history characteristics are identified that adaptCorallinato its dominant role in thi

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00248.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTCysts of the Antarctic prasinophytePyramimonas gelidicolaMcFadden were found in water samples from a fjord and a saline lake in the Vestfold Hills, Antarctica Unialgal cultures ofP. gelidicolafrom Ace Lake produced cysts. After ca. five weeks, tile cysts settled and adhered to the bottom of the culture flask. The cyst wall was covered by a scale type not seen on the flagellated cells; however, the base of the cyst scale was similar to the box scales ofP. gelidicolamotile cells. Cyst scales were also found off the continental shelf in Prydz Bay.In a 1.7 m sediment core taken from Ace Lake, both cyst scales and box scales ofP. gelidicolaoccurred at most depths. Differences in the ratio of these two scale types at different depths in the core may indicate past ecological changes in the lake. Upper sediments of the core were dated at 5310 ± 90 yrs B.P., indicating that prasinophyte scales may be recognizably preserved for extended periods.P. gelidicolawas widely distributed in saline lakes of the Vestfold Hills with salinities of 3.2–133% and temperatures ranging from – 5.0 to 10.4°C. This is the first report of encystment ofP. gelidicolaand, to our knowledge, is the first record of a prasinophyte with two distinctly different scale types occurring on cells during different stages of the life hi

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00249.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe seasonal abundance of epilithic algae was correlated with major physico‐chemical parameters in a first‐order, heavily shaded stream in northern Arizona. Diatoms made up over 85%, by numerical abundance, of the epilithon community Light energy, water temperature, and stream discharge were most highly correlated with seasonal abundance of epilithic diatom taxa when analyzed with stepwise multiple regression. None of the chemical variables measured in the study (NO3‐N, O‐PO4, SiO2, including PH) was found to be significantly correlated with the seasonal community structure of epilithic diatoms. Total diatom cell densities showed a significant negative correlation to stream bed light energy. Likewise, total diatom cell densities along a transect in the stream bed showed a negative correlation to current velocity during those months when base flow was low and stable, and current velocity was ≤25 cm·sec‐1. Most diatom taxa had highest cell densities at temperatures<16°C and at daily mean stream bed light levels400 μE·m−2·s−1. Blue‐green algae (cyanobacteria) grew best at the highest recorded water temperatures and daily mean stream bed light energy (16–20°C and 900–1200 μE·m−2·s−1). Abrupt increases in NO3‐N coincided with a brief pulse ofNostoc pruniformecolonies during June, and

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00250.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTThe effect of steady‐state nitrogen limitation on photo‐synthetic characteristics and growth efficiency was examined in the marine haptophyteIsochrysis galbanaGreen. Nitrate limited chemostats were maintained at nine dilution rates, ranging from 0.18‐0.96 d−1, under continuous irradiance levels of 175 μmole quanta·m−2·s−1, an irradiance level which saturated photosynthesis at all growth rates. Nitrogen limitation led to an overall reduction in pigmentation and a decrease in the cellular concentration of reaction centers; however, the optical absorption cross section, normalized to Chl a, increased. Moreover, Chl c/a ratios were higher in nitrogen‐limited cells: the change in Chl c/a ratios were correlated with an increase in the functional size of Photosystem II. Both light saturated photosynthetic rates normalized per cell and specific respiratory losses were positively linearly correlated with growth rate. Light saturated photosynthetic rates normalized to Chl a remained relatively insensitive to the rate of nitrogen supply. The minimum quantum requirement for gross photosynthetic oxygen evolution increased from 12.4 to 17.0 quanta/O2. At the growth irradiance, the quantum requirement increased 88%, from 19.9 to 37.5 quauta/O2Photosynthesis/respiration ratios remained relatively constant at dilution rates greater than 35% of the maximum relative growth rate. Consequently, net growth efficiency, defined as the ratio of the specific growth rate, μ, to specific gross photosynthesis, P, also remained relatively constant over this range of growth rates

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00251.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTUsing spectroscopic, biophysical and immunological techniques, we assayed the relative abundance often chloroplast proteins and protein complexes in the marine haptophyte, Isochrysis galbana Green, grown at nine steady‐state dilution rates in nitrogen‐limited chemostats. The proteins included Photosystem I reaction center (RCI) chlorophyll protein, CP1; Photosystem II reaction center (RC II) protein, D1; two chlorophyll a‐binding apoproteins, CP 43 and CP 47; 33 KDa oxygen evolving protein, OEC 33; α subunit of coupling factor, CF1α; large (LSU) and small subunits (SSU) of ribulose 1,5‐bisphosphate carboxylase, RuBisCO; the chlorophyll a/c/fucoxanthin protein complex, LHCP; and cytochrome b6/f. Seven of the ten protein complexes are encoded in the chloroplast, two are encoded in the nucleus and one shares chloroplast and nuclear genomes. Over the range of dilution rates (0.96‐0.18 d−1) cell N decreased 42% and cellular chlorophyll a decreased 50%; however, the stoichiometric proportion of RC II: cytochrome b6/f: RC I remained constant, averaging 1:3.3:0.8. In contrast, RuBisCO / PS II decreased by 58%. The light harvesting chlorophyll a/c/fucoxanthin protein complex increased relative to RC II; however, as cells became more nitrogen limited the fraction of total cell nitrogen contained in RuBisCO decreased from 21.3 to 6.7%, whereas that of the light harvesting complex remained relatively constant, averaging 6.8%. Our results generally support the hypothesis that in nitrogen limited cells, proteins encoded in the nuclear genome are synthesized preferentially over those encoded in th

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00252.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTA laboratory experiment was conducted for 75 days to examine how irradiance levels and grazing influence algal biomass and community structure. Twelve laboratory streams were used for experimental analyses, with four channels exposed to one of three irradiance levels (15, 100, or 400 μE·m−2·s−1). Three of the four stream at each light level were stocked with the snailJuga silicula(250·m−2), leaving one stream at each light level without snails. Grazed stream exposed to low light levels developed low amounts of algal biomass (<2 g AFDW·m−2) and were dominated by adnately attached diatoms. Mean algal biomass increased over time in the grazed streams exposed to intermediate light; by day 75, these streams were characterized by moderate algal biomasses (30‐40 g AFDW·m−2) and filamentous chlorophytes. Algal assemblages in high light, grazed channels had high levels of biomass at day 43 (70 g AFDW·m−2) that declined to 30 g AFDW·m−2at day 75 and were dominated by chlorophytes. Among ungrazed streams, algal biomass at day 75 was relatively low in the low light streams (<7g AFDW·m−2) and was dominated by adnately attached diatoms. Ungrazed streams exposed to intermediate and high light levels had moderate biomasses (23 and 19 g AFDW·m−2, respectively) and were dominated by chlorophytes and large diatoms. Grazing appeared both to delay and alter successional trajectories of algal assemblages, with alterations most noticeable during early seral stages at intermediate and high light levels. Grazing had the least effect on successio

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1989.tb00253.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY