摘要:

ABSTRACTQuantitative cytological and fatty acid composition was determined for the diatom Cyclotella meneghiniana Kütz, Data from four separate experiments were examined to elucidate changes that may occur with respect to daily photoperiod. Overall, fatty acid composition is similar to that reported for other diatoms with the exception that the C16 fatty acids constitute approximately 70% of all fatty acids. The major fatty acids are C14:0, 16:1, 16:0, 18:0, and 20:5. Fatty acids that are present in minor amounts are iso‐14:0, iso‐15:0, 15:0, 17:0, 18:4, 18:2, 18:1, 19:0, 20:0, 22:0, and 23:0.Cytological composition is similar to that previously reported with the chloroplast and vacuole being the largest compartments within the cell. Changes in both cytological and fatty acid composition were studied with respect to the light / dark cycle. Chloroplast and lipid relative volume are greatest during the early part of the dark period. Nuclear relative volume is lowest in the dark and increases throughout the light period.Total unsaturated fatty acids, including the C20:5 fatty acid, are lowest in the early part of the light period and highest in the dark. The sum of the C16 fatty acids remains constant at 70% of total fatty acids in the cells throughout the light/dark cycle, although percent composition of these two fatty acids shifts.The data suggest that cyclical changes occur in both quantitative morphology and fatty acids composition with respect to daily photoperiod. The cells, although not rigidly synchronized, most likely divide in the latter part of the dark period or in the first hours of the light period. Lipids increase dramatically in the dark. The ecological implications of lipid storage are discussed in relation to lipophilic toxic

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04448.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04150.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTHypoglossum rhizophorumsp. nov. is described from deep coral reef habitats on the southern insular shelf of Puerto Rico and the western insular shelf of Basse Terre, Guadeloupe, occurring from 21 to 85 m in depth. The new species is also known from a single shallow‐water collection in Hawaii. Plants grow from a prostrate nonfoliose rhizome producing simple, delicate erect blades at regular intervals. Reproductive plants were not collected in the field; isolated plants, however, readily reproduced in culture demonstrating a typical“Polysiphonia‐type” life history. Spermatangial sori form coalesced oblique bands which are interrupted by secondary cell rows. Tetrasporangia are produced from both lateral and transverse pericentral cells, adjacent second‐ and third‐order cells as well as cor

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04449.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTA natural assemblage of freshwater phytoplankton was removed from an oligotrophic lake and grown at N:P supply ratios of 5:1, 15:1 and 45:1 (by atoms) in semicontinuous culture. After a minimum of 31 days at an average daily growth rate of 0.5 d−1, experiments were conducted examining the time‐course of saturated ammonium uptake rates. Cultures grown under the two lowest N:P supply ratios demonstrated greatly elevated initial, specific uptake rates for ammonium and were able to sequester between 7 and 21% of their daily N requirement in less than 5 min. The initial rates declined rapidly but were followed by a subsequent increase and decrease over a 120 min per

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04450.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTThe potent neurotoxin saxitoxin, and possibly several of its derivatives, are localized in two types of sites within the marine dinoflagellateGonyaulax tamarensisLebour. Immunocytochemical techniques using a polyclonal antibody and epifluorescence microscopy demonstrate toxin localization within the nucleus as well as on the periphery of small granules thought to be starch grains. In the nuclear region, the labelling occurred on or close to the permanently‐condensed chromosomes as well as in an area within the two arms of the nucleus in the vicinity of the nucleous. No binding was observed in a closely‐related, non‐toxic dinoflagellate. Different binding affinities were observed between the nucleus and the grains at high and low antibody dilutions. This may relate to the polyclonal nature of the antiserum and to the presence of multiple toxins within theG. tamarensisisolate studied. Mechanistic interpretations of these labelling patterns remain speculative, especially the localization of the antigen at the outer edge of starch grains, but the distinct labelling in the nuclear region suggests that saxitoxin, with its two positively charged guanidinium groups, may bind to nucleic acids or nuclear proteins in a manner analogous to the polyamines and other cations. The labelling patterns reported here suggest that the saxitoxins may not simply be secondary metabolites but instead could be important compounds involved in the structure and function of theG. tamarensisg

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04451.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTDiel vertical migration byHeterosigma akashiwo(Hada) Hada (Raphidophyceae) was monitored in a 1.5 in tall microcosm. Vertical stratification, with low salinity and low orthophosphate (Pi) concentration in the upper layer and high salinity and high Piconcentration in the lower layer, was simulated in the tank, analogous to summer stratification in the Seto Inland Sea. The phosphate metabolism of H.akashiwo during this vertical migration was studied using31P‐NMR spectroscopy. At night this species migrated to the lower phosphate‐rich layer and took up inorganic phosphate (Pi) which then was accumulated as polyphosphate (PPi) by an increase in the chain length of PPiDuring the daytime this species migrated to the phosphate‐depleted surface water and utilized the accumulated PPifor photophosphorylation by decreasing the chain length of PPiDuring the first night after the phosphorus was introduced to the previously impoverished waters, the cells took up inorganic phosphate, accumulating the new phosphorus nutrient internally as PiBut the cells did not convert Pito PPipresumably due to their lack of ATP. After the second day of the experiment, conversion of Pito PPiat night was much more rapid than on the first day, presumably due to increased ATP availability. Then the cycle continued, with uptake of Piand conversion to PPiat night at the bottom and its utilization during the day at the surface. These data suggest that the role of PPiin the metabolism of this species appears to be as a phosphate pool which regulates the level of Piand ATP in the cell. Diel vertical migration allows this red tide species to shuttle between the phosphate‐rich lower layer and the photic upper layer in stratified waters.31P‐NMR is shown to be a valuable tool in studying the phosphorus metabolism in migrating

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04452.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04151.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTValve morphogenesis in two Surirellae (S. ovalis Brebisson and S. robusta Ehrenberg) is described. Mitosis takes place at the broad end of the cell. After cleavage, a new Microtubule Center (MC) arises near each spindle pole and moves to the adjacent plasmalemma. Soon, a specific group of microtubules (MTs) extends from very near the MC around the periphery of the cell. Concurrently, the new tubular Silica Deposition Vesicle (SDV) grows around the periphery of the cell close to these MTs. A double rib of silica is rapidly formed inside the SDV; the space between the ribs becomes the raphe. Mitochondria line up along the MTs, and the SDV may be molded around these to create the canal raphe. Soon, the SDV expands in two directions to create the face and the mantle of the new valve. Meanwhile, each daughter nucleus, accompanied by the MC, moves to its interphase position at the center of the cell; this movement is colchicine‐sensitive. As in several other pennate diatoms, an interruption in the raphe of the mature valve coincides with the initial position of the MC. The canal raphe thickens rapidly around the mitochondria; a rudimentary raphe fiber may be associated with the creation of a tiny curvature at the inner raphe fissure. As the SDV expands in the large S. robusta, the daughter cell protoplasts slowly shrink by plasmolysis, thereby creating the complex curved surface of the new valve surmounted by the arching canal raphes which are now quite rigid. In S. ovalis, the daughter cell protoplasts remain appressed and therefore the new valve surface is basically flat.The symmetry of Surirella is quite different from that of other pennate diatoms. However, the cytoplasmic events accompanying valve morphogenesis are similar in all important respects to those described in other raphid pennate diatoms, and clearly supports a naviculoid origin for this genu

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04454.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTPrimary production rates of edaphic algae associated with the sediments beneath four monospecific canopies of vascular plants were determined over an annual cycle in a Mississippi salt marsh. The edaphic algal flora was dominated by small, motile pennate diatoms. Algal production (as measured by14C uptake) was generally highest in spring‐early summer and lowest in fall. Hourly rates ranged from a low of 1.4 mg C/m2in Juncus roemerianus Scheele to a high of 163 mg C/m2beneath the Scirpus olneyi gray canopy. Stepwise multiple regressions identified a soil moisture index and chlorophyll a as the best environmental predictors of hourly production; light energy reaching the marsh surface and sediment and air temperature proved of little value. Adding the relative abundances of 33 diatom taxa to the set of independent variables only slightly increased R2; however, virtually all variables selected were diatom taxa. R2was only 0.38 for the Spartina alterniflora Loisel. habitat but ranged from 0.70 to 0.87 for the remaining three vascular plant zones. Annual rates of algal production (g C/m2) were estimated as follows: Juncus (28), Spartina (57), Distichlis spicata (L.) Greene (88), and Scirpus (151). The ratio of annual edaphic algal production to vascular plant net aerial production (EAP / VPP) was 10–12% for the first three habitats and 61% for Scirpus. Chlorophyll a concentrations, annual algal production rates, and EAP / VPP values were comparable to those determined in Texas, Delaware, and Massachusetts salt marshes but lower than those reported for Georgia and particularly California mars

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04455.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

ABSTRACTAn axenic clonal culture of Chattonella antiqua (Hada) Ono was grown on a 12: 12 h LD cycle in a laboratory culture tank containing 1 m3of f/2 medium. Diel changes in mean cell volume, cellular carbon (carbon content per cell), C/N ratio, cellular Chl a, Chl a/c ratio and carotenoid composition were observed. Mean cell volume and cellular C, N and pigments increased during the light period as a result of photosynthesis and decreased with increase of cell concentration by phased cell division during the dark period. These changes indicated that carbon assimilation and pigment synthesis occurred together during the light period. However, the patterns of increase were not the same since different diel patterns were also found in the ratios of C/N and chl a/c. Photosynthetic pigments were analyzed by reversed‐phase high‐performance liquid chromatography with ion‐pairing solution. This analysis showed that the dominant carotenoids in C. antiqua were fucoxanthin, violaxanthin and β‐carotene. Diel patterns of Chls a and c were similar to that of fucoxanthin but different from those of violaxanthin and β‐carotene. The cellular contents of Chl a, fucoxanthin and carbon increased in a parallel manner during the light period. On the other hand, the increase of violaxanthin was restricted to only a few hours at the beginning of the light period during cell divi

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1988.tb04456.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY