摘要:

SUMMARYResults from the present study suggest thatChara brauniiencompasses a complex of geographical races or incipient species that although morphologically similar, are isolated to varying degrees ranging from partial interfertility to complete reproductive incompatibility. Most of the 6 clones studied were interfertile to the extent that fertilization was followed by the development of black oospores, but subsequent germination tests disclosed that many of these either failed to germinate or gave rise to offspring that were partially or completely sterile. No support was encountered for the suggestion thatC. brauniiis of recent development or that it has been distributed rapidly throughout the world.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02401.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYThe development of the carposporophyte inKallymenia reniformisinvolves an elaborate series of interactions between reproductive and vegetative tissues. Following fertilization, the inner cells of the carpogonial branches form processes that unite with the supporting cell and with each other, giving rise to a large fusion cell. A number of medullary filaments are enveloped and incorporated within the developing fusion cell. Secondary filaments may be produced from medullary cells outside the fusion cell after connecting filaments have been initiated.Connecting filaments are nonseptale and wind their way through the medulla. The presence of a connecting filament in the vicinity of an auxiliary cell appears to initiate a complex sequence of responses. Vegetative filaments are produced in the medulla and inner cortex that grow centripetally toward the auxiliary cell and fuse with one another, forming a network of secondary tissue. One of the vegetative cells may penetrate the auxiliary cell, while others intrude into subsidiary cells connecting them with the network. An ostiolate pericarp is initiated in the cortex above the auxiliary cell. The connecting filament fuses with the auxiliary cell and also with some of the surrounding vegetative cells, forming an irregular lobed structure. Gonimoblast is initiated in scattered pockets from vegetative cells in the vicinity of the auxiliary cell apparatus.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02402.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYThe influence of 113 combinations of temperature (9, 12, 18, 25, 30 C), salinity (5–35 ‰ at 5 ‰ intervals), and light (4 levels) on the mean daily cell division rate (K) of the Narragansett Bay clone ofRhizosolenia fragilissimawas examined following appropriate preconditioning. Growth did not occur below 9 C, but was excellent (K =∼1.2) under certain combinations of light and salinity at 12, 18, and 25 C. The optimal salinity of 20–25 ‰ was temperature independent. Growth was not measurable at 5 ‰, although survival occurred. At 20 ‰ and 1200 ft‐c,Kincreased approximately 1.8‐fold from 0.65 to ∼1.2 between 9 and 18–25 C.The optimal light intensity was generally 600 ft‐c, although several light‐temperature‐salinity trends were found. At 10 ‰ at all temperatures, the mean daily division rate decreased with increasing light above 600 ft‐c, a response found at all salinities at 12 C, but not at other temperatures. Between 15 and 25 ‰, at 18 and 25 C, mean growth was independent of light intensity; at 30–35 ‰ a direct relationship with light may be present with maximum growth occurring at 1200–1800 ft‐c.Thein situandin vitroresponses ofRhiz. fragilissimato salinity and the optimum and upper temperature levels are in general agreement. However, growth failure below 9 Cin vitrois at odds with reports that natural populations occur even at −1.11 C. The questions of to what extent this discrepancy reflects the occurrence of thermal clones, different taxa, and/or experimental artifacts are briefly discussed. It is suggested that naturally occurring populations found below 9 C might be designated asRhiz. fragilissimaf.faeröensis, and thatRhiz. fragilissimaf.bergoniibe used for populations growing at higher temperatures, until this matter is resolved.Obs

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02403.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYUsing gamma spectroscopy, measurements were made of the uptake of cobalt and vitamin B12by a number of species of tropical macroalgae, particularlyLaurencia corallopsisandEnteromorpha lingulata.Data were gathered on the manner in which uptake rates are influenced by illumination and how they change with time during incubation and with substrate concentration. Some information is included on uptake rates when cobalt and vitamin B12were provided separately and together.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02404.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYApparentKmvalues for nitrite reductase, glutamic dehydrogenase, and nitrate reductase are of the order 10−4molar for nitrite, ammonia, and nitrate, respectively while half‐saturation constants for the corresponding uptake mechanisms approximate 10−6molar. Ammonium and nitrate are accumulated in the vacuolated cells of the diatom (about 10 and 40 mmoles/liter cell volume, respectively) and these intracellular pools serve as substrate for the assimilatory enzymes. Nitrite is either not accumulated or is concentrated, in a very small cellular compartment.Ammonium and nitrate in the external medium exert modifying effects on uptake and assimilatory mechanisms which can be distinguished from effects of the ions accumulated within the cells. Several of these effects are described and fitted into a general scheme of nitrogen assimilation byD. brightw

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02405.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYSome ecologically important phytoplankters released vitamins into culture medium during growth.Skeletonema costatumandStephanopyxis turris(vitamin B12‐requirers) produced both thiamine (vitamin B1) and biotin when growing with either 12 or 2 ng vitamin B12/liter.Gonyaulax polyedra(vitamin B12‐requirer) produced thiamine with 12 ng vitamin B12/liter, andCoccolithus huxleyi(thiamine‐requirer) produced vitamin B12and biotin with 120 ng thiamine/liter, but only biotin with 10 ng thiamine/liter. The amount of vitamin produced by an alga and rate at which it was produced varied with the phytoplankter, the concentration of the required vitamin, and incubation time. Vitamins produced during early and exponential growth were due to excretions, and those produced at stationary growth resulted from excretion and release due to cell lysis.Uptake of the required vitamin by all phytoplankters was greatest during the first few days of incubation. On continued incubation the rate of uptake/cell decreased.In the sea phytoplankters may contribute a major portion of the amount of dissolved vit

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02406.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYNutrient enrichment experiments were conducted with a Narragansett Bay clone ofRhizosolenia fragilissimato examine the potential influence of nutrients in regulating its seasonal cycle in this embayment, and their contribution to its coastal tendencies. Growth rates were measured at 18 C and 1000 ft‐c continuous illumination in surface waters enriched in 15 different ways. Narragansett Bay was sampled in March, May, September, and December. Six stations on a transect from this Bay to the Sargasso Sea were sampled during late summer.The data and our previous autecological observations are consistent with the idea that the annual cycle of this species in Narragansett Bay is associated with temperature, chemical “water quality,” and unknown factors. Its absence during late fall and winter may reflect low temperatures and a trace metal (Co, Mo) inadequacy. In early spring, low temperature appears to be the limiting factor, whereas in late spring and early summer trace metals again appear to prevent active growth. A late summer‐early autumn bloom occurs periodically during optimal temperature conditions; this can terminate independently of grazing pressure, and in spite of seemingly adequate light‐temperature‐salinity and phosphate

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02407.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYGrowth and chlorophyll synthesis by the green algaGolenkiniacease after approximately 60‐hr incubation in 0.01Msodium acetate. These effects are immediately preceded by a rapid rise of the pH of the medium to 8.6–8.8 due to acetate uptake. The pH kinetics are due to a gradual loss of the phosphate buffer, not to the induction or activation of acetate assimilatory enzymes. However, neither high pH nor sodium acetate alone is sufficient to inhibit cell division and bleach the algae; both must be present. Additional experiments support the hypothesis that acetate alters the cells so that they become sensitive to high concentrations of OH

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02408.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYAlthough most sexually reproducing strains ofRhodochorton purpureumare dioecious, an isolate from Chile is monoecious. The tetrasporophyte of the monoecious strain differentiates directly from the fertilized carpogonium as in the dioecious strains but it differs slightly in its development.

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02409.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY

摘要:

SUMMARYThe pH of the main body of thermal water and of the outlet of Waimangu Cauldron (Frying Pan Lake) is 3.8, whereas hot springs flowing into this lake are alkaline, pH 8.2–8.7. Where these waters meet there are pH gradients, and it is possible to find a series of habitats differing in pH but having approximately the same temperature (54–56 C). Where the pH is above 4.8 the blue‐green algaMastigocladus laminosusis present, and where the pH is below this value the eucaryotic algaCyanidium caldariumis the sole photosynthetic microorganism at temperatures less than 55 C. Rocks resting on the bottom of Waimangu Cauldron surrounded by water of pH 3.8 haveMastigocladus laminosusgrowing on them, but measurements of pH directly in these algal mats showed that the microenvironment of the alga was actually above pH 4.8. A simple experiment showed that it is probably the rock,per se, that initiates a tiny island of alkalinity in the acid lake, permittingM. laminosusto become established. The outlet of Waimangu Cauldron is a hot acid stream which becomes progressively alkaline as it descends through Waimangu Valley, due to inflow of alkaline water from springs and a cold stream. Blue‐green algae were found in this stream when the pH was greater than 5.0 andC. caldariumwhen the pH was less than 4.0. In one region where the pH was between 4.0 and 5.0, both blue‐green algae andC. caldariumwere seen, although in moribund state. These data, provide further information on the lowest pH values at which blue‐green algae are a

ISSN:0022-3646    

DOI:10.1111/j.1529-8817.1970.tb02410.x

出版商:Blackwell Science Inc    

年代:1970

数据来源: WILEY