ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00209.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe in situ primary production of three common under‐story members of the Rhodophyta in South African west coast kelp beds was determined monthly for a year using dissolved oxygen techniques. Strong seasonal patterns of photosynthesis and respiration were evident in all three species. Net photosynthesis of all three species was greatest in spring (October) and lowest in winter (June). Increasing photosynthesis in late winter coincided with increasing ambient irradiance and photoperiod, whereas decreasing photosynthesis in summer was not explained by changes in the environmental parameters measured. We suggest that this may he due to an innate pattern related to some other seasonal plant activity such as reproduction. Seasonal Pmaxand Ikvalues reveal that the obligate understory species,B. proliferaandE. obtusa,are shade‐adapted whereasG. radula,a low intertidal and shallow subtidal dominant, is sun‐adapted. Low C: X ratios consistent with a high nutrient environment and high rates of productivity were found in all three species. Net photosynthesis to respiration (Pn:R) ratios were fairly constant forB. proliferaandE. obtusa,implying that then photosynthetic processes were governed more by seasonal variations in irradiance than by instantaneous light availability. The Pn: R ratio ofG. radulawas variable, suggesting that this species is more responsive to rapid fluctuations in irradiance and may therefore be adapted for rapid growth during periods of high irrad

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00214.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTChanges in the biochemical composition of sea‐ice microalgae (southeastern Hudson Bay, Canadian Arctic) were used to assess the light and nutrient status of cells growing at the ire‐water interface. These changes allowed us to test the hypothesis that ire algae are limited by light at the beginning of their growth season and become periodically limited by nutrients as the season progresses. During the vernal growth season, three patterns of variation in cellular components were found in response to changes in environmental conditions. 1) Chlorophyllsaandc,ATP, carbohydrate, and carbon followed the seasonal increase in under‐ice irradiance, which was mainly mused by melting of the snow cover. 2) Dissolved and biogenic silicon underwent periodic variations, which were coupled to the fortnightly neap‐spring cycle of tidal mixing. 3) Cellular contents of free amino acids, protein, and total nitrogen remained relatively constant during the season. An early decrease in intracellular chlorophyllsaandcsuggests that ire algae did respond to small changes in solar irradiance by changing the pigment composition of their photosynthetic units. Seasonal increases in ATP, carbohydrate, and total carbon indicate light limitation in April, followed in May by a period of excess irradiance and/or nutrients in short supply. The seasonal increase in ATP and the high values of the ratio free amino acids: protein show that neither phosphorus nor nitrogen limited algal growth at the ire‐water interface. In May, higher values of carbohydrate: protein, carbon: nitrogen, carbon: chlorophylla,and also carbon: silicon and ATP: silicon indicate that the ice algae became silicon‐deficient in their natural environment. Following a period of light limitation, at the beginning of the season, ice‐algal growth became silicon‐limited, when in situ irradiance and the accumulated algal biomass were high and the tidally‐driven nutrient supply was not strong enough to satisfy algal nutr

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00220.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTPhysiological differentiation of the heteromorphic life‐history phases of the red algaMastocarpus papillatus(C. Agardh) Kützing was assessed. Photosynthetic responses to light and temperature of the erect, foliose gametophyte were compared to those of the crustose tetrasporophyte. Plants of both phases were collected from four locations on the Pacific coast of Baja California, Mexico, and California, USA, between 32–4l° N latitude. Within each location, the chlorophyll‐specific, light‐saturated photosynthetic rates of gametophytes were generally five times greater than those of tetrasporophytes. Initial slopes of photosynthesis: irradiance curves were greater for gametophytes than for tetrasporophytes. The crust and the blade from each location were similar with respect to dark respiration rates. For tetrasporophytes from all locations, the photosynthetic temperature optima were between 12–15° C. The photosynthetic temperature optima for gametophytes ranged from 15–17° C for plants from Trinidad Head (41° N) to 22–25° C for plants from Punta Descanso (32° N). Both gametophytes and tetrasporophytes from the northernmost location had significantly higher photosynthetic rates than the same phase from the other three locations. The photosynthetic responses to light support models for the life history in which life history phases have different ecological roles. The gametophyte, thought to be specialized for rapid growth and competition, may allocate more resources to photosynthetic machinery, hence the higher maximum photosynthetic rates. The tetrasporophyte, thought to be specialized for resistance to herbivores, may allocate more resources to structural or chemical defenses in preference to photosynthetic machinery. Consequently, the tetrasporophyte has lower pho

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00232.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTParasitic fungi infected anAsterionella formosaHass. population for 10 months of the year, during which time the population density of the alga was over 100 cells‐L−1. High injection rates of more than 20% of the cells were observed between February and July except on a few occasions such as late April and late June. Mortality of infected diatom cells was temperature dependent in dialysis tube culture experiments; the loss rate of field populations due to fungal injection also was affected by temperature. Loss rates of diatom cells were negligibly small m February even though infection percentages were more than 20%, but increased toward summer with an increase m temperature. High infection percentages and correspondingly high loss rates (e.g. 0.3 d−1) occurred periodically during the summer. The results suggest that this type of host‐parasite interaction is an important control of algal population size in natural

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00239.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe biomassof Cladophora glomerata(L.) Kütz. was estimated at selected sites in the Colorado River between Glen Canyon Dam, Arizona, and River Kilometer 354.C. glomeratabiomass was significantly higher at sites above Lees Ferry (25 km downstream from the Dam) than sites below the Ferry. Biomass and chlorophyllawere significantly reduced whenC. glomeratawas subjected to one‐time exposures to the atmosphere for 12 daylight h in more. Repeated 12/12 h and 24/24 h (exposure/submergence) cycles over a two‐week period also showed a significant reduction in biomass. The adaptations ofC. glomeratato “stranding” during regulated flows are d

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00244.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTChanges in cell size and silica content were examined in response to aluminum additions in cultures of the acidophilic diatomAsterionella ralfsiivar.americanaKörn at pH 6.0. The effects of Al were examined over a range of steady‐state growth rates using silica‐limited semicontinuous cultures (Si:P = 8.0). Additions of ≥ 2.8 μmol · L−1total Al decreased mean cell length, total surface area, and biovolume up to 40–50%. The effects of Al were dependent on growth rate with the magnitude of size reduction increasing at higher growth rates. The proportion of small (approximately 15–20 μm) cell length classes increased relative to large (approximately 50 μm length) cell length classes when total Al exceeded 2.8 μmol · L−1, particularly at higher growth rates. The relationship between cell quota and steady‐state growth rate fit a Droop relationship at 0 and 2.8 μmol·L−1total Al, but this fit was highly variable in the presence of Al. Cell quotas in the 6.22 μmol·L−1total Al treatment were highest at low growth rates; therefore, a Droop relationship was an inappropriate descriptor of growth rate. Cells also became 30–40% more heavily silicified per unit surface area in the presence of Al and at growth rates ≥0.22 day−1. Although the mechanisms responsible for size reductions in response to Al additions are unclear, the relationship between metal concentration and frustule morphology may be useful as an indica

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00250.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTNew strains of the hydrocarbon rich algaBotryococcus brauniiKützing were isolated from water samples collected in three tropical freshwater lakes. These strains synthesize lycopadiene, a tetraterpenoid metabolite, as their sole hydrocarbon. The morphological and ultrastructural characteristics of these algae are similar to those reported for previously described strains which produce either alkadienes or botryococcenes. The pyriform shaped cells are embedded in a colonial matrix formed by layers of closely appressed external walls: this dense matrix is impregnated by the hydrocarbon and some other lipids. We believe the new strains synthesizing lycopadiene form a third chemical race inB. braunii,besides the alkadiene and botryococcene races, rather than a different species.Like the other two types of hydrocarbons, lycopadiene was produced primarily during the exponential and linear growth phases. The major fatty acid in the three races was oleic acid. This fatty acid was predominant in the alkadiene race; palmitic and octacosenoic acid also were present in appreciable amounts in the three races. Cholest‐5‐en‐3β‐ol, 24‐methylcholest‐5‐en‐3β‐ol and 24‐ethylcho‐lest‐5‐en‐3β‐ol occurred in the three races; three unidentified sterols also were detected in the lycopadiene race. Moreover, the presence of very long chain alkenyl‐phenols in the lipids of algae of the alkadiene race was not observed in the botryococcene and lycopadiene races. Of the polysaccharides released in the medium, galactose appeared as a primary component: it predominated in the botryococcene race. The other major constituents were fucose for the alkadiene race and glucose and fucose for the lycopadiene race. Although morphologically similar, some important chemical differences exist

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00258.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTRhodella reticulataDeason, Butler and Rhyne produces copious amounts of a viscous polysaccharide (VP) during growth in batch cultures. The VPs accumulated on the cell surface and in the culture medium once cells ceased growth; starch concurrently accumulated within the cells. Light‐saturated14C‐uptake declined steadily as the cells aged. Net synthesis rates for starch and mucilage were two‐ and four‐fold lower, respectively, in non‐growing cells than in growing cells, while the relative partitioning of newly‐fixed carbon into these materials was not different. These data suggest that total photosynthetic loading, rather than partitioning into one specific pool, controls cellular synthesis rates. No preferential synthesis of VPs occurred during the stationary phase. The findings have important implications for the commercial produc

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00266.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY

摘要:

ABSTRACTThe effects of temperature, ionic composition, and conductivity on growth rates of ten strains ofChaetoceros muelleriLemmerman (mostly var.subsalsumJohan.&Rushf.) were studied. Lipid content of stressed and unstressed cells and fatty acid composition were also determined. Considerable physiological variability was observed in the ten strains, although principal components analysis of physiological data indicated that all strains fell into one of two major groups:C. muelleri(var.muelleriand var.subsalsum)and an undescribedChaetocerosspecies morphologically close toC. muellerivar.subsalsum.A high degree of agreement was found among morphological, physiological, and biochemical data sets, indicating that physiological and biochemical data may be helpful in making taxonomic decisions in diatoms, particularly in taxa with few morphological characters. We also conclude that nonmorphological characters such as those employed in the present study can be used to test phylogenetic hypotheses formulated from traditional morphological data.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1990.00271.x

出版商:Blackwell Science Inc    

年代:1990

数据来源: WILEY