GROWTH OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) IN A CYCLOSTAT: COMPARISON OF DIURNALLY CONSTANT AND FLUCTUATING LIGHT INTENSITIES.
Item
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Title
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GROWTH OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) IN A CYCLOSTAT: COMPARISON OF DIURNALLY CONSTANT AND FLUCTUATING LIGHT INTENSITIES.
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Identifier
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AAI8112346
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identifier
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8112346
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Creator
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COSPER, ELIZABETH MAHER.
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Contributor
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Prof. Thomas C. Malone
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Date
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1981
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Oceanography
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Abstract
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The effects of variations in light intensity on the photodaptive characteristics and efficiency of growth of Skeletonema costatum (Grev.) Cleve were evaluated. The relative importance of changes in carbon specific rates of respiration and organic release to the efficiency of growth was determined. Light intensity was either constant during the light period at levels from 1500 - 15 (mu)Einstein(.)m('-2)(.)s('-1) or fluctuated throughout the light period from 500 to 10 (mu)Einstein(.)m('-2)(.)s('-1.).;Carbon specific particulate production rates were a saturating function of incident light intensity. Particulate carbon production rates per unit chlorophyll a were a linear function of light intensity up to 650 (mu)Einstein(.)m('-2)(.)s('-1). Full sunlight condition, 1500 (mu)Einstein(.)m('-2)(.)s('-1), did not induce photoinhibition of growth or gross production. Daily rates of growth remained uniform at approximately 1.00 day('-1) under comparable constant and fluctuating light regimes.;Under the diurnally constant light regimes the effects of variations in light intensity on cellular biomass characteristics were dominated by changes in the pigment content of cells. Chlorophyll a cell('-1) decreased from a maximal value at the lowest light intensity to a minimum at 650 (mu)Einstein(.)m('-2)(.)s('-1). Cell size as daily mean carbon cell('-1), nitrogen cell('-1), and cellular volume was unvarying under diurnally constant light conditions from 38 - 1500 (mu)Einstein(.)m('-2)(.)s('-1). In contrast, under diurnally varying light cell size decreased whereas daily mean chlorophyll a cell('-1) was unaffected.;Periodicity in cell division was observed only at light intensities of 130 (mu)Einstein(.)m('-2)(.)s('-1) or greater and was decreased under diurnally varying light. Under all light conditions carbon and pigment growth were maximal during the light period but relatively well coupled throughout the 24 hr period. Carbon production during the dark period varied from 19 to 34% of total daily production and was a linear function of growth rate.;Net growth efficiency varied from 0.69 to 0.38 and was maximal at 130 (mu)Einstein(.)m('-2)(.)s('-1). Variations in light reduced net growth efficiency from this optimal level mainly as a consequence of relative changes in respiratory activity. Total daily respiration was a positive linear function of growth rate except at the highest light intensity and under fluctuating light when respiration was greatly enhanced. A disparity between respiratory loss and total respiration increased with light intensity and the refixation of respired carbon was proposed as the process which could account for the observed conservation of carbon within the cell. Organic carbon release increased with light intensity and under fluctuating light but remained less than 10% of gross production under all light conditions. When carbon production and division were most in phase, efficiency was maximized. Cellular chemical fractionation indicated that under high or variable light conditions, when growth efficiency was reduced, fixed carbon was stored during the light period for subsequent synthesis of protein and pigments, and division at night.(' ).
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Biology
