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A comparative analysis of wild and laboratory grown Laminaria abyssalis (Phaeophyta) using modulated fluorescence (1993)

Rodrigues, M. A. ; Yoneshigue-Valentin, Y. ; Santos, C. P.

Springer

Hydrobiologia 260-261 (1993), S. 463-469

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ISSN: 1573-5117

Keywords: Laminaria ; modulated fluorescence ; chlorophyll ; blue light ; light adaptation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Laminaria abyssalis fronds were either collected at the Brazilian costal area - 40 meters below sea level - or grown in the laboratory. The photochemical yield as defined by the Fv/Fm and the Fo - the dark fluorescence level when all PSII centers are open - varied with the distance from the stipe to the tip of the blade in wild grown fronds while it stayed constant in the laboratory grown plants. The chlorophyll a/c ratio levels decreased in the wild fronds from 12 (near the stipe) to 6 near the top. The chlorophyll c content increased from 0.8 to near 1.7 mg cm−2 in the wild fronds. The laboratory fronds did not show variations in their chlorophyll contents. The wild fronds pattern changed after 2 months kept in the laboratory, producing similar results to those grown in the laboratory. The results indicate that the levels of the antenna complex in the wild fronds increase from the stipe to the top of the blade, in a fashion similar of the sun/shade leaves. Also, results show, that this alga is able to adapt itself to new light conditions, possibly increasing its level of antenna complex and photosynthetic units.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00049057

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Use of an internal reference in 13C chemical shift measurements (1990)

de Kowalewski, D. G. ; de Los Santos, C. ; Marceca, E.

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 28 (1990), S. 1-4

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ISSN: 0749-1581

Keywords: Internal reference ; 13C chemical shift measurement ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The use of the nominal value of the chemical shift of the solvent to calibrate the spectrometer in 13C NMR spectroscopy was found to introduce errors due to the effect which the solute has on the solvent. In addition, hexamethyldisiloxane (HM) is proposed as an internal standard; owing to its high boiling point it is easier to manipulate than tetramethylsilane (TMS) and it is therefore possible to prepare solutions of known concentrations. In order to convert the data obtained with this standard to the TMS scale, the chemical shift of HM was determined in 16 solvents using cyclohexane as external standard in a spherical cell (5% w/w concentration of HM) as a function of the solvent factor g2. Comparing these results with a similar plot obtained previously for TMS by other workers, it is possible to convert one type of data to the other by a simple linear expression.

Additional Material: 2 Ill.