摘要:

ABSTRACTMore than 1000 spores from 11 species of red algae were collected; their differences in size and sinking rates were measured using a new micro‐video technique. A relationship between size and sinking rate was shown with larger spores generally sinking faster than smaller ones. Variability in spore size, or lack thereof, is a species characteristic.Cryptopleura violacea(J. G. Ag.) Kylin andNeoagardhiella baileyi(Kutz.) Wynne and Taylor were found to produce a wide range of spore sizes. Such variability in size may be related to differences in spore formation. Centrifugation was used to separate the contents of spores to show differences in them. The ecological implications of these observations are considere

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00828.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTContinuous cultures ofMerismopedia tenuissimaLemmerman, limited by phosphorus, nitrogen, sulfur, or carbon, were compared to non limited batch cultures by two methods. The cellular content of photosynthetic pigments (chlorophyll and phycocyanin) was found to decrease in all nutrient limited cultures, except for the carbon limited culture. The ratio of carbohydrate to protein was 4‐ to 7‐fold higher in P, N or S limited cultures than in non‐limited or C limited cultures. The macromolecular products of photosynthesis were determined in samples to which NaH14CO3was added. Relative incorporation into protein decreased in P or N limited cultures, increased accumulation of low molecular weight compounds was found in S and P limited cultures, and little change was noted in C limited cultures as compared to non‐limited cultures. Although relative incorporation into protein was significantly greater at 20μEin·m−2·s−1light intensity than at 180 μEin·m−2.s−1in non‐limited cultures, this effect was abolished in all nutrient limited cultures. These results suggest that measurement of the cellular carbohydrate to protein ratio and the products of photosynthesis would be useful in the analysis of algal populat

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00829.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTA “planted core” system was developed to test the effect of short term (1–2 weeks) experimental manipulation of environmental parameters on edaphic microalgae under field conditions. A large number of small cores (surface area = 7 cm2) were collected, randomized and replanted in the marsh in fiddler crab exclosures with appropriate experimental treatments. Daily enrichment of the cores with NH4+resulted in significant increases in edaphic primary productivity and levels of chlorophyllain both summer and winter seasons in the short‐Spartinamarsh. Enrichment with a complete nutrient solution caused no further increases. Nutrient enrichment of creekbank sediments was much less stimulatory to the resident algal assemblage. In both sites, but especially in the creekbank, the removal of fiddler crab grazers resulted in significant increases in chlorophyllaand productivity. Experimental manipulation of light intensity showed that the average light intensity reaching the sediment surface was saturating for chlorophyll production in the short‐Spartinamarsh. A reciprocal transplant experiment involving unfertilized cores from the short‐Spartinamarsh and creekbank marsh demonstrated that NH4+inputs occurring in the creekbank site rapidly alleviated nitrogen limitation of edaphic algae from short‐Spartinamarsh. Algae in creekbank cores incubated in the short‐Spartinamarsh were unable to sustain high productivity once the original standing stock

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00830.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe production and extracellular release of cyclic adenosine 3′: 5′‐monophosphate (cAMP) by the blue‐green algaAnabaena flos‐aquae(Lyngb.) Breb. varied greatly within and between active growth phase and stationary phase and under differing nutrient regimes. Enhanced cellular cAMP production was found in actively growingAnabaenainoculated into media deficient in nitrate or phosphate, or into fresh media containing non‐limiting nutrient concentrations. In stationary phaseAnabaena, but not actively growing cells, the concentrations of intra‐cellular cAMP present in cells grown under a variety of nutrient regimes could be significantly correlated to [14C]‐bicarbonate uptake by an exponenti

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00831.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTChlorella emersoniiShihira et Krauss var.emersoniiexhibits ‘C4‐like’ gas exchange characteristics when grown at air levels of CO2, but is ‘C3‐like’ when grown with extra CO2. The total inorganic carbon concentration, and the free CO2concentration, averaged over the cell interior are higher in air‐adapted cells than can be accounted for by passive CO2equilibration from the medium and the mean intracellular pH value. The ‘extra’ inorganic C in the air‐grown cells probably cannot all be accounted for in terms of binding to proteins and requires an active transport process to account for it. The electrical potential of the cell interior becomes more negative when the ‘CO2concentrating mechanism’ is operative; this is most readily explained if the active step in inorganic C accumulation is primary active uniport of HCO3−. Since the ‘CO2concentrating mechanism’ can operate when CO2is the species crossing the outer permeation barrier, it is suggested that the site of active HCO3−transport inChlorella(and other eukaryotes) is the chloroplast envelope, and the plasmalemma in cyanobacteria. This scheme explains the obligatory role of the de‐repressed carbonic anhydrase in C4‐like photosynthesis in algae, but some other data support an explanation of C4‐like photosynthesis in terms of special properties of carbonic anhydrase as a carbo

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00832.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTDeveloping and released spermatia of the red alga,Tiffaniella snyderae(Farl.) Abb. were studied. Spermatia were observed under hydrodynamically defined conditions and found to be released from the exposed spermatangial heads in a spermatium‐plus‐strand unit that remained connected to the spermatangial head. Interactions of single‐spermatial strands resulted in the formation of multi‐spermatial strands as long as 600 μm with as many as 47 spermatia along their length; however, most were 100–200 μm with 8–21 spermatia. Strand length and number of spermatia were correlated. Spermatial strands contracted or extended and rotated as the water velocity past the plant was changed, and in still water the strands retracted into a clump on the spermatangial head surface. Each strand type exhibited a characteristic threshold water velocity at which it reached maximum length, and above which it broke and was carried away. Fluorescence microscopy showed that the strands did not contain nucleic acid (DNA) and could thus be differentiated from filamentous blue‐green algal and bacterial epiphytes. Histochemical staining indicated that the strands and spermatial vesicles contained an acidic, sulfated polysaccharide. Chelation of Ca2+with EGTA resulted in strand breakdown suggesting that this divalent cation may be involved in strand integrity.Scanning electron microscopy revealed that release from the spermatangia occurred through tears in the cuticle covering the spermatangial head if it was still present, or from exposed spermatangia. Individual spermatia were attached tangentially to a well‐defined strand 0.64 μm in diameter in the contracted state to 0.2 μm in the extended state. Transmission electron microscopy of spermatangial heads showed that immature spermatangia were characterized by a centrally positioned nucleus and abundant ER cisternae filled with a moderately electron dense granular material. Later in development the spermatangia acquire two spermatial vesicles containing highly convoluted fibrillar contents. The cell becomes polarized with the nucleus displaced apically and the spermatial vesicles occupying the basal half of the spermatangium. At maturity one of the vesicles is released basally. Liberated spermatia contain a membrane‐bound nucleus and mitochondria and are associated with an oblong accumulation of fibrous material similar in size and position to the strand observed with the SEM. These strands are discussed in relation to red algal fertilization and other phases of the r

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00833.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe major components of the internal flagellar apparatus ofChilomonas parameciumEhr. are two large microtubular roots and a striated root paralleled by three microtubules. The two microtubular roots overlap at the basal bodies. One microtubular root follows a curved path in the anterior of the cell, and the other extends straight to the posterior passing through a groove in the nucleus. The striated root extends laterally from the basal bodies. Except that it is smaller, the posteriorly directed root bears a strong resemblance to the axostyle of oxymonads. The overall arrangement and structure of the flagellar roots is similar to the pelta, axostyle and costa of trichomonads and the pelta and axostyle of oxymonads, groups of mitochondrion‐less, largely parasitic or symbiotic protozoans. An affinity between cryptomonads and oxymonads or trichomonads would have many phylogenetic implications, some of which are discusse

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00834.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTPithophora oedogonia(Mont.) Wittr. biomass in Surrey Lake, Indiana was greater in the littoral than in the pelagial region. Although mean soluble reactive phosphorus concentrations did not differ between the two areas, nitrate concentrations were almost six times higher in the cove than in the open water. Using laboratory cultures ofPithophora, the half saturation constant (Ksat 20° C relating filament growth to external concentrations of nitrate‐nitrogen was determined to be 1.23 mg L−1(=88 μM)and for phosphate‐phosphorus, 0.1 mg L−1(=3.22 μM). These values were used to calculate a NO3‐N/PO4‐P atomic ratio of 27.6. Comparison of this value with NO3‐N/PO4‐P ratios in Surrey Lake showed that nitrogen limiting conditions were prevalent in the open water section of the lake. Alkaline phosphatase and dark ammonia uptake analyses on field collected filaments from the shallow and deep water sections confirmed the hypothesis that nitrate is the major factor limiting growth ofPithop

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTThe development and ultrastructure of the male gamete ofSphaeroplea annulina(Roth) Agardh have been investigated. Multiple mitoses each associated with phycoplast microtubules occur as a result of nitrogen deficiency in the culture medium. A regular cleavage of the cytoplasm delineated by microtubules then occurs, resulting in many young male gametes. During maturation the gametes are retained within a vacuolar envelope. Maturation entails reduction in nuclear size and chromatin condensation, loss of chloroplast thylakoids, endoplasmic reticulum and Golgi apparatus. The apical region where the two flagella are inserted consists of an apical cone and fibrous connections which lie distal to the basal bodies. The study supports the suggestion put forward in a previous paper: namely that the genusSphaeropleabe retained in a separate order the Sphaeropleales.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

ABSTRACTIn extremely oligotrophic Lac Matamec (Quebec, Canada) the ultraplankton (<15 μm) represented 47% of total phytoplankton biomass but accounted for 71% of the primary production and was 2.5 times more photosynthetically efficient than larger phytoplankton. Cell surface area was a good predictor of efficiency, while cell numbers and bio‐mass were not. High surface:volume ratios may explain the high efficiency of the ultraplankt

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1981.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY