Showing papers in "Journal of Phycology in 1974"

Nitrogen assimilation of an oceanic diatom in nitrogen-limited continuous culture1

Abstract: SUMMARY The oceanic diatom Thalassiosira pseudonana Hasle and Heimdal (formerly Cyclotella nana) was grown with 12L:12D illumination cycles in nitrogen-limited continuous culture with a mixture of ammonium and nitrate as the N source Measurements included, at 3 different growth rates (degrees of N limitation), cell concentration, cell carbon, nitrogen, and chlorophyll a contents, cell volume, photosynthetic carbon assimilation vs irradiance, short-term uptake of ammonium and nitrate vs their ambient concentrations, and in vitro activities of the assimilatory enzymes nitrate reductase and glutamic dehydrogenase The various parameters showed either an increase (pattern a) or a decrease (pattern b) with increasing N limitation Those following pattern a were nitrate reductase activity and the capacity to assimilate nitrate and ammonium Those following pattern b were glutamic dehydrogenase activity, photosynthetic rate, nitrogen:carbon and chlorophyll a:carbon composition ratios Results are discussed in terms of the interpretation such measurement for natural phytoplankton and effects of circadian periodicity

Phosphate uptake under nitrate limitation by scenedesmus sp. and its ecological implications1

Abstract: SUMMARY Under nitrogen limitation the phosphate content of Scenedesmus sp. shows little variation regardless of growth rate and the N/P atomic ratio of the medium. P uptake therefore can be calculated as the product of P content and N-dependent growth rate. The maximum rate of P uptake in N limitation is lower by a factor of about 8 than the rate in P limitation. As reported earlier, P uptake by this alga under P limitation is described by the kinetics resembling non-competitive enzyme inhibition, with one or several intracellular P fractions as inhibitors. These fractions include surplus P (water extractable) and inorganic polyphosphate fractions A (acid soluble) and B, C, and D (acid insoluble). In N limitation, the ratios of fractions A, B, C, and D are quite different from the ratios of P limitation at comparable growth rates. The concentrations of polyphosphate fraction A in N-limited cells are much, higher than the levels in P-limited cells, and this fraction becomes more predominant at low growth rates in N limitation. This fraction, if introduced as the inhibitor into the noncompetitive scheme, explains the uptake kinetics in both N- and P-limited cells and the low maximum uptake rate in N limitation. This finding may have two significant ecological implications: (1) A nutrient imbalance which brings about changes in the internal, level or the metabolism, of fraction A would affect P uptake. (2) Nitrogen sufficiency would cause a competitive advantage in P uptake. This advantage would be shared by N2 fixers and algae with low optimum N/P ratios. In Scenedesmus sp. P limitation switches to N limitation and vice versa when the cell N/P atomic ratio is about 30.

Growth of vitamin b12‐requiring marine diatoms in mixed laboratory cultures with vitamin b12‐producing marine bacteria12

Abstract: SUMMARY The vitamin B12 requirement of several marine diatoms can be satisfied in B12−limited laboratory cultures by heterotrophic marine bacteria isolated from the same waters and from sediments. The bacteria can utilize diatom excretory products, or the remains of dead diatom cells, in the production of the vitamin. The growth of 12 B121− requiring diatoms (7 genera) in mixed cultures with 14 different bacteria (without added B12) was compared to the growth of those same diatoms in axenic cultures with excess added B12. Diatom growth was generally rapid in the first few days, followed by sustained, slower growth. The diatom yields in mixed cultures ranged from 0.8 to 84% of the yields in axenic cultures with added B12. In a detailed study of one mixed culture, increases in diatom densities were paralleled by increases in cell densities of the bacterium during the first few days of exponential diatom growth. During the period of slow diatom growth, when diatom densities oscillated but steadily increased, the decreases in diatom densities were associated with increased bacterial growth. This suggests that death of a fraction of the B12-limited diatom population releases sufficient organic matter to stimulate growth of the bacteria and their subsequent excretion of B12; this B12 in turn stimulates further growth of the diatoms. Diatom-bacteria interactions leading to the production of B12 may be important in maintaining viable populations of B12-requiring diatoms in nutrient-poor waters during periods between blooms, when conditions are unfavorable for rapid growth.

Studies on the autecology of the marine diatom thalassiosira nordenskiöldii cleve. 1. the influence of daylength, light intensity, and temperature on growth1

Abstract: SUMMARY The marine diatom Thalassiosira nordenskioldii Clave was grown at 48 different combinations of daylength (9:15, 12:12, 15:9 LD), light intensity (0.011, 0.027, 0.066, 0.100 ly/min [g cal/cm2/min]), and temperature (0, 5, 10, 15 C). Growth occurred at all combinations of light and temperature except at 15 C at the highest light level. Maximum growth (K = 1.8 doublings/day) occurred at 10 C under the 15:9 LD cycle. At 15 C the maximum rate was 1.7 doublings/day but occurred at the shortest day-length (9:15 LD). The maxima at 5 and 0 C were 1.32 and 0.67 doubling/day, respectively. At 0 C growth was similar over a wide range of light intensities (K = 0.6–0.65), with, maximum growth being attained at a much lower light intensity than at 5 C. Above 5 C there was a decrease in the light intensity at which maximum growth occurred and excessive light became inhibitory to growth. At 15 C the light intensity at which maximum growth occurred was greater with shorter day-lengths. The temperature optimum was 10 C at 15:9 and 15 C at 9:15 LD. The chlorophyll a content of the cells was greatest under low light intensities and short daylengths, while temperature had a variable effect. The response of Thalassiosira in the laboratory contrasts with, its apparent preference for low temperatures in nature (0–5 C). The experiments suggest that the termination of the bloom of Thalassiosira in Narragansett Bay and elsewhere is not solely temperature dependent.

An improved method for obtaining axenic clones of planktonic blue‐green algae1,2

Abstract: SUMMARY Axenic clones from 5 isolates of Anabaena flosaquae, 1 isolate of Microcystis acruginosa, and 1 isolate of Aphanizomenon flos-aquae were obtained by a combination of steps that provided a 1000-fold reduction in the bacteria-algae ratio and permitted bacteria-free filaments or cells to be isolated and grown from agar pour plates. The first step consisted of the addition of phenol to a dark-treated culture to selectively reduce the numbers of actively growing bacteria while leaving the resting algal cells viable. The next steps involved washing the treated algal suspension on a Millipore filter pad or membrane followed by plating in washed agar containing buffered mineral medium plus vitamins and soil extract. The final steps consisted of incubating the agar pour plates, coring bacteria-free filaments or cells, culturing the agar cores in a buffered mineral medium, and rigorously testing the resulting cultures for bacteriological contamination. Between 50 and 90% of the cores grew, and of these about 50% were judged axenic. The method, with appropriate adaptations, should be suitable for obtaining axenic clones of other freshwater and marine algae.

Two species of the chlorophyte genus ostreobium from skeletons of atlantic and caribbean reef corals1,2

Abstract: SUMMARY Two species of the siphonaceous chlorophyte Ostreobium inhabiting the aragonite skeletons of Atlantic and Caribbean reef corals were studied. Ostreobium quekettii Bornet & Flahault has been previously reported from these locations, but the species is here amended to include filament forms previously described under the name O. reineckei Bornet. Ostreobium constrictum sp. n. is described here for the first time. The 2 sympatric species are distinguished on the basis of filament morphology and chloroplast form.

Chloroplast structure and pigment composition in the red alga griffithsia pacifica: regulation by light intensity1

Abstract: SUMMARY The ratio of accessory phycobiliproteins to chlorophyll a is controlled by light intensity in the marine red alga Griffithsia pacifica The greatest changes in pigment ratios are observed below 300 ft-c; above 300 ft-c the response approaches saturation Ultrastructural examination of chloroplasts of plants grown at different intensities reveals that the number of phycobilisomes per unit of photosynthetic thylakoid changes in direct proportion to the pigment ratios and in inverse proportion to the light intensity

Algal excretion and bacterial assimilation in hot spring algal mats1

Abstract: SUMMARY Benthic algal-bacterial mats are present in the effluents of alkaline hot springs at temperatures between 50 and 73 C. The thin surface layer is composed of the unicellular blue-green alga Synechococcus lividus. Also present in the surface layer and forming thick, orange mats beneath it, are filamentous, phototrophic, gliding bacteria of the genus Chloroflexis, also capable of heterotrophic growth. The very low species diversity and the constancy of the hot spring environment, make these mats a good ecosystem for studying the transfer of nutrients from the algae to the bacteria. To determine whether the alga might supply organic materials to the bacterium, excretion by natural populations of S. lividus was studied in the field by means of short-term radioisotope experiments. Under optimal conditions for photosynthesis, between 3 and 12% of the total 14C fixed was excreted as 14C-labeled organic compounds. Variations in cell density at concentrations of S. lividus approximating those found in the mat had no effect on the percentage excretion. However, at cell densities below a threshold, level, the percentage excretion increased with diminishing cell density. Except at very low light intensities the percentage of fixed carbon excreted, was very similar for all light intensities tested. Excretion at temperatures approaching the upper limit for growth was not significantly different from the percentage excretion values observed at lower temperatures. 14C-labeled organic compounds excreted during algal photosynthesis could be subsequently assimilated by natural populations of the bacteria present in the mat.

Mitosis and cytokinesis in platymonas subcordiformis, a scaly green monad1

Abstract: SUMMARY Scaly green monads are often placed in a separate class, Prasinophyceae, and have been considered to be among the most, primitive of green algae. Platymonas possesses rhizoplasts which resemble sarcomeric structures. At prophase, extranuclear spindle micro-tubules emanate from a granular region which appears to arise through dissolution or dispersion of the rhizoplasts. It is probable that the rhizoplasts are largely consumed during the formation of the spindle and only small fragments are left at metaphase. The rhizoplasts can be seen again at telophase but are short at this stage. The basal bodies are not at the spindle poles but remain at their interphase position. The interzonal spindle collapses early at telophase, and shortly thereafter cleavage microtubules appear. These microtubules extend from the region of the basal bodies to the posterior of the cell. The events of cell division are compared with these events in other green algae and in Ochromonas. The functional and phylogenetic significance of the observations is discussed.

Cell division in chlamydomonas moewusii1

Abstract: SUMMARY Cell division in Chlamydomonas moewusii is described. The cells become immobile with flagellar abscission prior to mitosis. The basal bodies migrate toward the nucleus and become intimately associated with the nuclear membrane which is devoid, of ribosomes where adjacent to the basal bodies. The basal bodies replicate at preprophase. The nucleolus fragments at this stage. By prophase the basal body pairs have migrated, to the nuclear poles. Spindle fibers become prominent in the nucleus. The nuclear membrane does not fragment. The nucleus assumes a crescent-form by metaphase. Polar fenestrae are absent. Kinetochores appear at anaphase. An interzonal spindle elongates as the chromosomes move to the nuclear poles. Daughter nuclei become abscised by an ingrowth of nuclear membrane, leaving behind a separated, degenerating interzonal spindle. Ribosomes reappear on the outer nuclear membrane at late telophase. Nucleoli reform early in cytokinesis. The cleavage furrow, associated microtubules, and endoplasmic reticulum comprise the phycoplast. Cytokinesis proceeds rapidly after the completion of telophase. The basal body-nucleus relationship becomes reorganized into the typical interphase condition late in cytokinesis. Specific and predictable organelle rearrangements during mitosis have been described. Cell division in C. moewusii is compared with other algae, especially C. reinhardi.

Growth of two facultatively heterotrophic marine centric diatoms1,2

Abstract: SUMMARY The facultative, heterotrophs Cyclotella cryptica (sclone WT-1-8) and Coscinodiscus sp. were selectively isolated from coastal waters by dark incubation of organically enriched solid medium. C. cryptica grows in the dark with glucose and galactose, and Coscinodiscus sp. with glucose. Clone WT-1-8 of C. cryptica grows about twice as fast with glucose as a previously studied clone (0-3A). In the dark with, 5 × 10−6 M glucose C. cryptica divides every 3 days, while with 5 × 10−5 M glucose Coscinodiscus sp. divides every 10 days. Heterotrophic growth of either diatom for 1 year does not cause a major reduction in carbon, nitrogen, chlorophyll a, and chlorophyll c contents, or in photosynthetic ability, compared to light-grown cells. It is possible that facultative heterotrophy is of ecological benefit to these diatoms, probably for slow growth and survival during extended periods of dim light or darkness.

Fine structure of capitular filaments in the coenocytic green alga penicillus1,2,3

Abstract: SUMMARY Capitular filaments of Penicillus capitatus contain a large central vacuole. The parietal cytoplasm is densely packed, devoid of chloroplasts in the growing tip, and becomes convoluted and sponge-like as extensions of the vacuole penetrate the cytoplasm in mature portions of the filament. Structure of organelles and their distribution in the filament are described. The vacuole contains a variety of inclusions, such as membranous configurations, spherical bodies, electron dense bodies, and calcium oxalate monohydrate crystals, each of the latter surrounded by a chamber associated with microtubules. Endophytic bacteria are present throughout the vacuole and occasionally in the tip cytoplasm. Some vacuolar components of P. pyriformis are described for comparison.

Endocytosis of microcystis aeruginosa by ochromonas danica1

Abstract: SUMMARY Ochromonas danica Prings., a chrysomonad alga which demonstrates a high degree of nutritional versatility, is capable of feeding on the toxic blue-green alga Microcystis aeruginosa Kuetz. In this paper light microscopic, electron microscopic, and cytochemical examinations of endocytosis in O. danica are reported, with particular emphasis on the vicissitudes of endocytic and lysosomal activities during intra-cellular digestion. An interpretation of the function of organelles associated with endocytosis is presented.

Nutrient uptake kinetics in phytoplankton: a basis for niche separation1

Abstract: SUMMARY Daily patterns of incorporation of carbon dioxide and inorganic phosphate were measured in phytoplankton from Lake George, New York, in January and February 1972. Rates of photosynthesis oscillated in phase for the entire assemblage and for individual cells of the diatoms Asterionella, Tabellaria, and Fragilaria. The photosynthetic capacity was maximal in the early afternoon. Daily patterns of phosphate uptake were also rhythmic. At ambient concentrations the assemblage takes up phosphate maximally in the morning while individual cells of the large diatom take it up maximally in the evening. A kinetic analysis of phosphate uptake indicated 2 velocities of uptake for cells of Tabellaria and Fragilaria: a hyperbolic function at small and an apparently linear relationship at relatively large concentrations. The large diatoms, in contrast to the total assemblage, functioned maximally at 2 separate times of the day: in the evening at ambient levels and in the morning at 0.4 μM and larger concentrations. Temporal stratification of the nutrient niche may be achieved by several uptake mechanisms in the algal cell that function at different times of the day or with a variable uptake velocity.

The ultrastructure of carposporogenesis in the marine hemiparasitic red alga erythrocystis saccata1

Abstract: SUMMARY The ultrastructure of carposporogenesis for Erythrocystis saccata is described. The fusion and gonimoblast cells contain few organelles, and chloroplasts are in a proplastid state, with pit plugs between gonimoblast cells dissolving early in development. Carpospore development may be separated into 3 stages, the first stage being characterized by the appearance of straight-profiled dictyosomes, fibrous vesicles, and an increase of discoid thylakoids within the chloroplasts. During the second, stage the dictyosomes assume a curved profile and striped vesicles are formed by the endoplasmic reticulum. The third stage is initiated by the disappearance of striped vesicles and the appearance of straight-profiled dictyosomes secreting vesicles with cores. Mature carpospores consist of many cored vesicles, fibrous vesicles, and floridean starch grains. A single wall layer surrounds each carpospore since the carposporangial wall becomes incorporated into a mucilaginous matrix surrounding the spores.

Structure of the periplast of cryptomonas ovata var. palustris1,2

Abstract: SUMMARY The periplast of Cryptomonas ovata var. palustris is composed of polygonal plates which are delineated by shallow ridges. A small ejectosome is located at each corner of the plate area. The plate areas vary in size; they are smallest at the anterior and posterior ends and are largest in the middle of the cell with an average length of 0.5 μ and of width 0.4 μ. In cross section a plate area is composed of 2 distinct layers, an outer plasma membrane layer with a fine particulate, appearance, and an inner layer consisting of two sheets. The sheets of the inner layer have a striated lattice pattern with a periodicity of about 20 nm. In negatively stained preparations one lattice appears to underlie another at certain angles. Protease digestion removed polygonal shaped inner layer.

The significance of reproductive and spore germination characteristics to the systematic of the corallinaceae: nonarticulated coralline algae12

Abstract: SUMMARY This paper deals with reproductive and spore germination characteristics to the systematics of the nonarticulated coralline algae. As can the articulated coralline algae, the nonarticulated coralline algae may also he divided into 2 groups on the basis of their yearly reproductive cycles, spore dimensions, and spore germination characteristics: the Lithophyllum group and the Lithothamnium group. These 2 groups are basically identical with the Amphiroa and Corallina groups of the articulated coralline algae, respectively, so far as these 3 characters are concerned. The grouping of these representatives of the Corallinaceae into 2 groups—Amphiroa—Lithophyllum and Corallina–Lithothamnium—coincides with a grouping based on the manner of connection between cells of adjacent filaments.

Physiological investigations on alaria esculenta (l.) grev. (laminariales). i. elongation of the blade1,2,3

Abstract: SUMMARY A seasonal rhythm in blade elongation rate was observed in Alaria esculenta. Maximum (3.0–3.6 cm/week) and minimum (0.5–1.0 cm/week) rates were recorded in June and September, respectively. Translocation of growth-promoting metabolites occurs within the main blade and between the sporophylls and blade. Bidirectional flow of growth-promoting metabolities within the stipe was demonstrated. Seasonal effects of nutrients (NO3- and PO43-) and photoperiod on blade elongation were shown in long-term laboratory experiments. Control of seasonal blade growth by exogenous and endogenous factors is discussed.

Sporangial structure and zoosporogenesis in chorda tomentosa (laminariales)1,2,3

Abstract: SUMMARY Members of the genus Chorda represent the simplest form of sporophyte in the order Laminariales. The present study deals with reproduction in Chorda tomentosa, involving the initiation, growth, and structure of the sporangium and the process of zoosporogenesis. The simple tube-like sporophyte of Chorda tomentosa grows in diameter by means of repeated anticlinal divisions in a superficial meristematic layer known as the meristoderm. The onset of reproduction is marked by the conversion of the meristoderm from contributing cells to the vegetative plant body to producing 2 new cell types: paraphyses and sporangial mother cells. At the time of initiation, sporangial mother cells are crescent shaped and possess a densely staining cytoplasm. Sporangial mother cells increase in size, become ellipsoid, decrease in staining density, and undergo meiosis. After meiosis, sporangia increase in size while their nuclei undergo successive cycles of synchronous mitotic divisions. Sporangia increase to a maximum length of 120 μ;m at which time they possess the characteristic “cap” found in all members of the order studied thus far. At this stage the protoplast of the sporangium is organized into a peripheral layer of nucleus-chloroplast pairs and a central region of vacuoles. Cleavage furrows begin to form at the cell membrane and are met by furrows developing in the interior of the cytoplasm resulting in the division of the entire protoplast into separate units. Each unit is an individual zoospore. The biflagellate zoospores contain a nucleus, one chloroplast with eyespot, perinuclear Golgi, and several bodies of presumed storage carbohydrate. The occurrence of a small population of early developing sporangia is described. In essential details, the origin, development, and structure of sporangia in Chorda tomentosa are identical to all earlier observations in the Laminariales.

Mitosis, cytokinesis, and colony formation in the green alga sorastrum1

Abstract: SUMMARY Synchronous mitotic divisions produce multi-nucleate cells of Sorastrum. Perinuclear envelopes of endoplasmic reticulum and a virtually intact nuclear envelope enclose mitotic nuclei. Cytoplasmic cleavage, which shirts before the last round of Synchronous mitoses, gives rise to uninucleate fragments which differentiate to form zoospores. These zoospores are released into a spherical vesicle, presumably derived from the inner layer of the parental cell wall, in which they swarm actively before aggregating as a spherical colony. The roughly conical shaped zoospores apparently adhere laterally before withdrawing their flagella and extending horns and a stipe, which, following wall deposition, interconnects the cells at the center of the colony. The probable role of the microtubules, which underlie the plasmalemma of aggregating cells, in determining the shape of both the cells and the colony itself is discussed.

Growth of vitamin b12‐limited cultures: thalassiosira pseudonana, monochrysis lutheri, and isochrysis galbana1,2

Abstract: SUMMARY The growth rates of 3 species of phytoplankton were found to be dependent on the vitamin B12 concentrations in the media In batch cultures, the vitamin B12 half-saturation constants and standard errors were 039 ± 0042 μμg/ml for Thalassiosira pseudonana (clone 3H), 169 ± 024 μμg/ml for Isochrysis galbana, and 277 ± 165 μμg/ml for Monochrysis lutheri A chemostat was used to grow T pseudonana with vitamin B12 as the controlling factor In the chemostat the yield and standard deviation, 102 ± 21 × 104 cells/μμg vitamin B12, was the same as in the batch culture, 126 ± 13 ± 104 cells/μμg The chemostat half-saturation constant, 026 ± 0068 μμg/ml vitamin B12, and maximum growth rate were in agreement with those obtained in batch cultures Vitamin concentrations for maximum growth, rates were greater than those calculated necessary from yield data to give observed population densities similar to those in natural waters In the sea the effect of vitamin B12 concentration on growth rates may be complicated by low concentrations of other nutrients or the presence of inhibitors

The benthic algae of southern baffin island. i. epipelic communities in rivers1

Abstract: SUMMARY The epipelic algae found in 9 rivers of southern Baffin Island were investigated during the 1972 growing season. The overall assemblage consisted of 240 taxa, of which 200 belonged to the Bacillariophyta and, only 17 to the Chlorophyta. Members of the Bacillariophyta accounted for S7–100% by numbers and 44–100% by volume of the algae at most localities. The dominant taxa were Achnanthes kriegeri Krasske, A. marginulata Grun., and Tabellaria flocculosa (Roth.) Kutz. The Chlorophyta comprised. 0–7% by numbers and 0–30% by volume of the algae, with Cosmarium tinctum Ralfs, Cylindrocystis spp., and Mougeotia sp. being most common. The standing crop in the different rivers commonly exceeded 8 × 106 cells/cm2 (8 × 109μ3/cm2), and a maximum growth rate of 3.2 × 105 cells/cm2/day (3.2 × 108μ/cm2/day) was observed. Temperature and light are considered important, factors in the regulation of algal numbers, while nutrient supply in the overlying water, grazing by herbivores, wave action, and flooding appeared to have little effect.

Benthic algae of southern baffin island. iii. epilithic and epiphytic communities1

Abstract: SUMMARY Blue-green algae–mainly Aphanocapsa pulchra (Kz.) Rabh., Oscillatoria tenuis Ag., Schizothrix muelleri Naeg., and Lyngbyn spp.—were predominant, in the epilithic communities of Baffin Island rivers and lakes during 1972, usually accounting for more than 90% by numbers and volume of the total flora. Diatoms were only important early in the growing season (June) with Achnanthes marginulata Grun., A. kriegeri Krasske, and Tabellaria flocculosa (Roth) Kz. being most common. Standing crop in one river increased from near 0 in June to 6.0 × 104 cells/cm2 (2.2 × 108μ3/cm2) in July and back to near 0 again by October. Low levels of nitrate nitrogen probably limited algal numbers, while flooding, light, and grazing by herbivores appeared to have little effect. Changes in algal standing crop in the lakes followed much the same pattern as outlined above. However, the maximum amount of algae was considerably greater than that recorded from the rivers, reflecting the greater availability of nutrients. Lyngbya nana Tild. was the main algal species attached, to filaments of Mougeotia sp., reaching greatest development (5.0 × 104 filaments/cm2) during September. On the other hand, diatoms–mainly Ceratoneis arcus Kz. and varieties, Fragilaria spp., and Synedra spp.–were predominant in the community floating among the filaments with maximum standing crop (64.48 × 106 cells/g dry weight of Mougeotia) occurring in July. The small diameter of the Mougeotia filaments was probably the main factor limiting the size of both the attached and free-floating communities.

Micromorphology of a small dinoflagellate prorocentrum mariae-lebouriae (parke & ballatine) comb. nov.1,2,3

Abstract: SUMMARY The surface structures of the bivalvate dinoflagellate Prorocentrum mariae-lebouriae are described in detail. It has an almost spheroidal shape in face-view, a compressed saucer-shape in side view, with a distinct striated band at the edge of the cell. Its surface is covered with small spines in a regular pattern, with 450 nm distance between pairs. The spines are 100–120 nm wide and 200–300 nm long. There are 600–700 spines on each valve. At the anterior cell end, one of the values has a V-shaped depression which contains a specialized structure accommodating the 2 flagellar pores. The flagellar pores are-enclosed by 8 small, thick plates held together and to the values by sutures. The flagellar pore area consists of 2 distinct structures: an apical collar possessing a curved forked plate and a larger structure composed of an unbranched, plate. There are 2 flagellar canals located between the flagellar pore plates. Beneath each flagellar canal lies a row of 11 microtubules. A row of microtubules forming a microtubular cylinder is situated adjacent to the oblong flagellar canal near a simple pusule. The microtubular cylinder encircles electron dense bodies. The bases of the longitudinal and transverse flagella appear to lie at an angle to each other. The above features are illustrated with transmission and scanning electron micrographs.

A comparative study of cell division in trichosarcina polymorpha and pseudendoclonium basiliense (chlorophyceae)1

Abstract: SUMMARY Pseudendoclonium basiliense and Trichosarcina polymorpha are essentially identical with regard to the fine structural details of cell division even though one was previously classified in the Chaetophorales and the other in the Ulvales. Cell division in the 2 genera is also shown to be like that in Ulva, as previously suggested might be the case. The combination of mitotic and cytokinetic characteristics common to the 3 genera is distinctive: (1) precocious development of a thick cleavage furrow, (2) centrioles distinctly lateral to polar fenestrae, (3) collapse of the interzonal spindle at telophase, and. (4) a cleavage furrow not associated with microtubules. It is suggested that features of vegetative cell division presently provide the best, characteristics for defining the Ulvaceae and that the use of growth habit should be abandoned. Despite the fact that a phycoplast is not present, in these algae, it is concluded that their affinities lie with genera that do possess a phycoplast.

Morphology and nutrition of pandorina unicocca sp. nov.1,2

Abstract: SUMMARY Eleven strains of Pandorina unicocca sp. nov. were studied for morphological characterization. The species was delimited by having cells which contain a single basal pyrenoid and by colonies which have cells separate from each other in the colonial envelope. A defined medium was developed for 4 strains of P. unicocca and the nutritional requirements of these strains were examined. All 4 strains were capable of completely autotrophic growth and they could utilize nitrate, ammonium, or urea as nitrogen sources. Optimum growth was nuts attained at pH 8.0.

Isolation, growth, and physiology of acidophilic chlamydomonads1,2

Abstract: SUMMARY A buffered, chelated, defined medium was developed for isolation and growth of acid-bog flagellates and for physiological studies of bog chlamydomonads. Hydrogen ion tolerances of Chlamydomonas acidophila, C. sphagnophila 121 A, C. sphagnophila IU293, and, C. reinhardi were determined. Only C. acidophila grew at pH 2.0. It did not grow at pH 7.0 or 8.0 as did the other chlamydomonads tested. Liver fraction “L” and Fe permitted growth of C. acidophila at pH 2.0 equal to control growth at pH 5.0. Neither C. sphagnopliila 121A nor C. reinhardi grew at pH 2.0 with these additions. Hydrogen ion seems to be excluded from the cell interior of acid-tolerant species. They remained green (ie, pheophytinization did not occur) when cultured below pH 5.0. C. acidophila grew in the dark with glucose as sole source of carbon and energy. Acetate, glycolate, and glyoxylate were assimilated in the dark if glucose was also present. C. sphagnophila 121A did not grow in the dark on any of the 51 organic carbon compounds tested. C. acidophila and C. sphagnophila 121A seem promising tools for determining biochemical mechanisms responsible for differences in H+ tolerances. Presumably specialized cell walls or membranes are involved.

The effect of daylength and light intensity on the growth rate of the marine diatom detonula confervacea (cleve) gran1

Abstract: SUMMARY The influence of 40 combinations of temperature (2, 7 C), light intensity (50, 200, 600, 1200, 1800 ft-c), and photoperiod (24, 15:9, 12:12, and 8:16 LD) at 30% salinity on the rate of cell division of the Narragansett Bay clone of Detonula confervacea (Det-1) was examined following appropriate preconditioning. At 2 C Detonula is a long day species (24 L) and prefers low light intensities (200–600 ft-c); poorest growth occurred at 12:12 and 8:16 LD, and the compensation intensity was about 10 ft-c. Increasing temperature to 7 C increased the mean growth rate, reduced the optimal daylength (15:9 LD), even though Detonula remained a long day species and increased the optimal light intensity (600–800 ft-c). The compensation intensity varied with daylength and ranged from about 10–50 ft-c. Photoperiods of 12:12 and 8:16 LD were least favorable for growth at both temperatures; light limitation and inhibition were observed at 50 and 1800 ft-c. respectively; inhibition was less pronounced at 7 C. There is some indication that the conditions of growth that the stock cultures were exposed to prior to preconditioning for use in the experiments may have sometimes influenced response. Detonula produced resting spores without nutrient depletion at 2 and 7 C at all light intensities when the photoperiod was lengthened. Auxospore formation was also observed. Although short daylengths (9:15 LD) limit Detonula's growth during the early stages of the winter bloom, it competes successfully against Skeletonema costatum initially. This results from its higher rates of growth and of photosynthesis at the prevailing temperature and light conditions and a lower compensation intensity than reported for Skeletonema. The main causes of Detonula's growth inception and termination in Narragansett Bay differ.

Enrichment of surface freshwater microlayers with algae1

Abstract: SUMMARY Using a variety of techniques for sampling micro-layers in freshwater environments, the frequent occurrence of significant and striking differences in algal community structure and densities relative to subsurface water is demonstrated.

Uptake of organic, compounds by two facultatively heterotrophic marine centric diatoms1,2

Abstract: SUMMARY Glucose and galactose uptake ability in Cyclotella cryptica (clone WT-1-8) and glucose uptake ability in Coscinodiscus sp. develop rapidly in the dark. Induction of sugar uptake ability in the dark does not require the presence of sugar in the medium. The sugars are taken up by carrier-mediated systems. In C. cryptica glucose and galactose are probably taken up by the same system. The capacity of glucose uptake in this recently isolated clone of C. cryptica is nearly 5 times that of a previously studied clone (0-3A). Other organic compounds, which by themselves do not support heterotrophic growth, can be taken up and respired by both diatoms at considerable rates compared, to glucose and galactose. Therefore, in nature, these diatoms may be able to utilize a variety of dissolved organic compounds as sources of intermediary metabolites and as respiratory substrates.