摘要:

ABSTRACTEpilithic and epiphytic diatoms were collected monthly from 18 June 1979 through 19 May 1980 from both shaded and unshaded sites of Sessums Creek, a shallow, oligotrophic and strongly alkaline stream in northeastern Mississippi. The dominant macroalgae were filamentous green algae belonging to the non‐mucilage producing generaCladophoraandRhizoclonium.Ninety taxa were identified withNavicula minimaGrun. andNitzschia dissipata(Kütz.) Grun. accounting for 50% of all valves counted. Other important taxa wereNavicula menisculusvar.upsaliensis(Grun.) Grun.,N. cryptocephalavar.veneta(Kütz.) Rabh.,Achnanthes minutissimaKütz. andCymbella turgida(Greg.) Cl. With few exceptions, the more dominant taxa were equally abundant in the shaded and unshaded sites and also in the epilithon and epiphyton. Species diversity (H') and the number of taxa in a sample in all four habitats showed an identical pattern, being lowest in winter and highest in fall. No one pair of habitats was more structurally similar than any‐other pair when compared by a similarity index (SIMI). Apparently, differences in light intensity and substrate type had little effect on diatom distribution in Sessums Creek and it was concluded that the locality sampled supported a single, nearly homogeneous diatom com

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00123.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTA new species of endolithic cyanophyte,Hyella gigasLukas and Golubic (Order: Pleurocapsales), differs from other species ofHyellaby its larger cell and filament dimensions and its laminated, often pigmented sheath. It bores into mollusk shells and other marine carbonate substrates on the east coast of North America, the Bahama Islands and the Northern Mediterranean Sea, where it is found from near mean low water down to 25 m depth. This comparatively shallow maximum depth is probably due to the limited capacity ofHyella gigasto adapt to changing light quality and intensity. We reject the suppression of the genusHyellaas proposed by Drouet and Daily.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00129.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTChromosome number and morphology as well as reproductive seasonally were examined inBangiapopulations collected from 88 sites along the British Columbia coasts. Sexual filaments were recorded at 35 sites and asexual filaments at 58. Four different types ofBangiawere determined. These were characterized by reproductive state and chromosome number, as well as by their seasonally and range of distribution. A summer‐fall three‐chromosome sexual type occurred from approximately 50° N northward and a winter‐spring four‐chromosome sexual type had a northerly limit of approximately 54° N, extending to the southernmost areas of British Columbia. Two asexual types occurred, exhibiting little seasonally, six‐chromosome populations throughout the coast and three‐chromosome populations at three southerly sites only. Karyograms were prepared for the four chromosomal types, assigning tentative centromere locations. Somatic chromosome pairing was reported for the first time in t

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00136.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe in situ productivity ofBotryocladia pseudodichotoma(Farl.) Kyl. andRhodymenia californicavar.californicaKyl., two common understory macrophytes inMacrocystis pyrifera(L.) C. Ag. forests, was determined once per month for one year. Gross productivity forB. pseudodichotomawas highest in October (1.23 mgC · g dry wt.−1· h−1), but rates were generally greater in spring and lower in summer. Respiration was variable throughout the year, especially in proportion to gross productivity. Gross productivity forR. californicavar.californicawas also highest in October (4.62 mgC · g dry wt.−1· h−1), and lowest in summer. Respiration was highly variable throughout the year. Deep (11 m) populationso/B. pseudodichotomahad 50% higher productivity than shallow (3 m) populations when incubated in shallow water, and 45% higher productivity when incubated in deep water. Populations ofB. pseudodichotomagrowing in shade at 3 m had 77% higher productivity than populations growing in sun at the same depth when incubated in a sun exposed location at 3 m. Respiration of the shade‐adapted plants was only one‐half that of the sun‐adapted plants. In comparison with similar studies in other sub‐tidal communities, net productivity of these two understory red algae is somewhat lower. Lack of strong seasonal productivity patterns and the highly variable underwater light regime suggests that understory algae may be adapted for rapid growth during short periods of high light, regardless

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00146.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe flagellar apparatuses of the quadriflagellate zoo‐spores and biflagellate female gametes of the marine chaetophoracean algaEntocladia viridisReinke are significantly different from those of algae belonging to Chaetophoraceae sensu stricto, but closely resemble those of ulvacean genera. These differences permit the taxonomic reassignment of certain marine chaetophoracean genera and an evaluation of the flagellar apparatus features used to characterize the class Ulvophyceae. Critical features of the zoospore include arrangement of the four basal bodies into an upper and a lower pair with the proximal ends of the upper basal bodies overlapping, terminal caps, proximal sheaths connected to one another by striated bands, and a cruciate microtubular rootlet system having a3‐2–3‐2alternation pattern and striated microtubule‐associated components that accompany the two‐membered rootlets. An indistinct distal fiber occurs just anterior to the basal bodies, and is closely associated with the insertion into the flagellar apparatus of the three‐membered rootlets. The flagellar apparatus demonstrates 180° rotational symmetry, and its components show counterclockwise absolute orientation when viewed from above. Newly described features include the prominently bilobed structure of the terminal caps on the upper basal body pair, and the presence of both a granular zone and an additional single microtubule anterior to each of the four rootlets, an arrangement termed the “stacked rootlet configuration.” Rhizoplasts were not observed and are presumed to be absent. The gamete is identical, except for the absence of the lower basal body pair and the presence of an electron‐dense membrane associated structure that resembles the mating structure found inUlvagametes. These findings, correlated with life history data, sporangial and gametangial structure and developmental patterns, chloroplast pigment arrays, and vegetative cell ultrastructural features, compel the removal ofEntocladia viridisand similar members of the marine Chaetophoraceae to a separate family, the Ulvellaceae. The latter is referred to the order Ulvales of the Ulvophyceae. The counterclockwise absolute orientation of components, and terminal caps, may be the most consistent flagellar apparatus features of ulvophycean green algae, while variations in other features previously considered diagnostic for the Ulvophyceae may serve instead to identify discrete lineag

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00153.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTA new species in the Liagoraceae (Nemaliales) having vegetative and male reproductive characteristics usually associated with the genusHelminthorais assigned toHelminthocladia(asHelminthocladia andersoniiSearles&Lewis) on the basis of the shape of the conical carpogonial protoplast, three‐celled carpogonial filament, development of the carposporophyte from both cells formed by division of the zygote and development of the involucre without the formation of a bridge around the zygote or formation of rhizoids from the involucre. All of these are consistent characteristics ofHelminthocladiaand distinguish its species from those ofHelminthor

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00164.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe effect of light quantity (irradiance) on the photosynthetic physiology of seven seaweed species was distinguished from the effect of light quality (color). Plants were grown in outdoor, continuous‐flow tanks, at irradiances saturating and limiting to growth, and in spectral distributions that were either broadband (white) or narrowband (green). The green light field complemented the absorptance spectrum of phycoerythrin and approximated the spectral distribution of a submarine light field in turbid coastal water near the compensation depth. Physiological measurements, made after 6–15 days growth, included light‐harvesting pigment densities, instantaneous photosynthesis‐light relationships and growth rate. In all experiments, these photosynthetic properties were independent of spectral distribution (color) and in most experiments were dependent on irradiance. These data do not conform to the predictions of the theory of complementary chromatic adaptation for s

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00173.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTThe effects of N2, nitrate and ammonia as N sources were investigated in P‐limited and nutrient‐sufficient cultures ofAnabaena flos‐aquae(Lyngb.) Bréb. The maximum growth rate (μm) was highest at 1.34 d−1with ammonia, compared to 1.18 with nitrate and 0.95 d−1with N2. There was no difference in P requirement between N2and nitrate cultures. Under P‐limited conditions, the increase in cell P with growth rate (μ) was identical. With N2as the N source, cell‐N concentrations in P‐limited cells increased with μ as did cell P, and the cellular N:P ratio remained the same (14) within the range of μ examined. With nitrate, however, cell N concentrations were high and independent of n, except at a low μ. It appears that this organism fixes atmospheric N2only at the minimum concentration required to maintain a μ. The acetylene reduction rate increased with μ in both N2‐and nitrate‐grown cells, but the rate was lower in nitrate. Under P‐limitation, there was no difference in net C‐fixation rate per cell between N2and nitrate cultures at a given μ. However, the rate per unit of chlorophylla(chla) was higher in N2than in nitrate cultures, and the rate was independent of μ with N2but was a linear function of nitrate supplied. The maximum C‐fixation rate in nutrient sufficient cells was highest with ammonia, followed by nitrate and N2. The cellular chlaconcentration was correlated with the total cell‐N concentration

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00179.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTChlamydomonas reinhardiiDangeard was grown in continuous culture under P limitation at a range of dilution rates. Carbon uptake measurements were performed using double isotope (12C/14C) techniques and the fluxes of carbon in the light and dark were analysed over the range of growth rates.14C uptake was shown to be equal to gross photosynthesis only at maximum relative growth rates; at low relative growth rates14C uptake approximated net photosynthesis. The altered pattern of C uptake was found to be due to the suppression of dark respiration in the light and the release of14C02from respiratory pathways at low relative growth rates. Metabolic channelling of14C from photosynthetic pathways to respiratory pathways occurred at low growth rates as the specific activity of the respired CO2reached 45% of the input gas mixture. These data are discussed in the light of the controversy concerning the measurement of gross and net photosynthesis in natural populations and in the light of models of14C uptake in single celled algae. Existing models are shown to be adequate for high relative growth rates but not for low relative growth rates under P limitation.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00185.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

ABSTRACTAkinetes ofPithophora oedogonia(Mont.) Wittrock, formed in stationary phase cultures, were induced to germinate by transfer to fresh media. Changes in various physiological parameters were monitored during the first 20 d of germination. Ungerminated akinetes contained a greater percentage of lipid, starch, and dry matter and exhibited lower photosynthetic rates than did vegetative cells. Germination consisted of four phases. Phase I (day‐0 to day‐1) was marked by a rapid increase in respiratory rates. Phase II (day‐2 to day‐6) involved protrusion of the germination tube and was insensitive to cyanide, a respiratory inhibitor, and simazine, a photosynthetic inhibitor. Phase III (day‐7 to day‐14) was marked by rapid elongation of the germination tube, increasing photosynthetic rate, increasing chlorophyll and water content and declining levels of lipid and starch. Germination tube elongation during phase III was not inhibited by simazine, but was cyanide sensitive. Phase IV (day‐15 to day‐20) was characterized by a reduction in respiratory rate and an abrupt increase in the ratio of photosynthesis to respiration. Germination tube elongation during phase IV was inhibited by simazine. The data indicate that germination inPithophora oedogoniaakinetes consists of an extensive period (phases I, II and III) during which reserve materials are respired. Utilization of internal food reserves apparently permits akinetes to germinate and supports the initial growth of the germination tube in light limited mi

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1983.00193.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY