Effects of N‐source, light intensity and temperature on nitrogen metabolism of bahiagrass

1985 ◽  
Vol 8 (10) ◽  
pp. 945-963 ◽  
Author(s):  
M.S. Fernandes ◽  
R.O.P. Rossiello ◽  
M.E.S. Bendix
Keyword(s):  
Light Intensity ◽  
Nitrogen Metabolism ◽  
N Source

Highly Specialized Nitrogen Metabolism in a Freshwater Phytoplankter, Chrysochromulina breviturrita

1987 ◽  
Vol 44 (4) ◽  
pp. 736-742 ◽  
Author(s):  
John D. Wehr ◽  
Lewis M. Brown ◽  
Kathryn O'Grady
Keyword(s):  
Nitrogen Metabolism ◽  
Laboratory Culture ◽  
Organic N ◽  
Acidic Precipitation ◽  
Inorganic N ◽  
Culture Study ◽  
N Source ◽  
Softwater Lakes ◽  
N Metabolism ◽  
N Compounds

A field and laboratory culture study was carried out on the nitrogen metabolism of isolates of the freshwater phytoplankter Chrysochromulina breviturrita Nich. (Prymnesiophyceae). These were isolated from two different softwater lakes, one believed to be influenced by acidic precipitation (Cinder Lake) and another which was experimentally acidified with H2SO4 (Lake 302-South). The alga was able to utilize only NH4+ as an inorganic N source. A range of irradiances and molybdenum concentrations failed to induce NO3− utilization. Among 17 organic N compounds including amino acids, purines, and other amines, only urea plus Ni2+ as a cofactor would serve as the sole N source for this species. Nonetheless, growth rates in media supplied with urea were significantly less than with NH4+. Field data from Lake 302-S indicate that a predominance of NH4+ versus NO3− as the major inorganic N species may have favored the development of a Chrysochromulina-dominated community during August 1984. A detailed depth profile also indicated that a metalimnetic peak (> 20 × 106 cells/L) of this alga coincided with a distinct NH4+ depletion, which occurred at no other time during the year. Experiments with isolates of C. breviturrita and a Nannochloris sp. (Chlorophyceae) (~ 1 μm in diameter) from this community indicated that the former alga possessed a highly specialized N metabolism much like the Cinder Lake isolate. The Nannochloris sp. from the same environment grew on NO3− and NH4+ equally well. It is suggested that the specialized NH4+ utilization by C. breviturrita may itself influence the pH regime of poorly buffered waters through selective NH4+ uptake and H+ generation.

Climate, nitrogen and grass. 3. Some effects of light intensity on nitrogen metabolism.

1971 ◽  
Vol 19 (3) ◽  
pp. 184-188
Author(s):  
B. Deinum
Keyword(s):  
Light Intensity ◽  
Nitrogen Metabolism ◽  
Perennial Ryegrass ◽  
High Light Intensity ◽  
High Light ◽  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Nitrate Content ◽  
Light Intensities ◽  
Water Soluble Carbohydrates

Between 18 May and 29 June 1966, a 2-year-old sward of perennial ryegrass was grown at normal (390), low (88) or high (711 cal/cm2 day) light intensity and given 20-160, 40-320 and 80-360 kg N/ha at the 3 light intensities, respectively. At low rates of N, high light intensity exhausted the nitrate reserves of perennial ryegrass, diminished the CP content, but greatly increased the percentage of water-soluble carbohydrates. With high N, high light intensity decreased nitrate content but increased both CP and water-soluble-carbohhdrate content. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

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