Biomedical subjects

E L Kruger

Publications and source records attributed to E L Kruger.

4 recordsLinked to original sources

PubMed2001

Light-mediated constraints on leaf function correlate with leaf structure among deciduous and evergreen tree species.

Leaf structure has been shown to be an important determinant of leaf photosynthetic characteristics, yet the nature of this relationship remains ambiguous. It has been suggested that intra-leaf shading of chloroplasts may explain the negative influence of increasing leaf thickness/density on mass-based photosynthesis. To explore further the importance of light-mediated functional limitations conferred by leaf structure, we examined photosynthetic responses to high unidirectional and bidirectional irradiances among broad- and needle-leaves ranging widely in mass per area (LMA). Except for leaves with the lowest LMA (< 40 g m-2), photosynthesis increased in bidirectional irradiance, and the ratio of unidirectional to bidirectional photosynthesis (Au/Ab) was strongly and negatively related to LMA, approaching 0.5 for the thickest/densest leaves. Bidirectional illumination also increased stomatal conductance, but the magnitude of stomatal response was modest and uncorrelated with LMA. Consequently, the ratio of intercellular CO2 partial pressures during unidirectional versus bidirectional irradiation was positively related to LMA. Hence, it appears that many C3 leaves may not be "light saturated" under high unidirectional illumination. The negative, exponential Au/Ab-LMA relationship in this study supports the notion that, as LMA increases, an increasing fraction of leaf chloroplasts are functioning at subsaturating irradiance under unidirectional light.

Carbon Dioxide↗

PubMed1993

Geographic variation of cuticular hydrocarbons among fourteen populations of Aedes albopictus (Diptera: Culicidae).

Cuticular hydrocarbons were used to differentiate among fourteen Aedes albopictus (Skuse) populations from Asia, Brazil, and the United States. Forty cuticular hydrocarbon peaks from each North American population were previously identified using gas chromatography electron impact-mass spectrometry. The same cuticular hydrocarbon peaks were identified in the Asian and Brazilian populations. Samples from three populations were analyzed using capillary gas chromatography chemical ionization mass spectrometry. Total carbon number and branch points were found for four peaks which occurred at equivalent chain lengths > 38.65. Quantitative analyses were performed by flame ionization gas chromatography. All populations contained the same cuticular hydrocarbons but showed differences in percentage composition. Nine of the 14 populations were separable by discriminant analysis of hydrocarbon components. Overlap of the 95% CIs occurred between the two Brazilian populations and among three North American populations. Individual specimens from three North American populations were used as a test group in the discriminant analysis. Correct classification of these individuals by population ranged from 80 to 100%.

Aedes↗

PubMed1991

Cuticular hydrocarbon geographic variation among seven North American populations of Aedes albopictus (Diptera: Culicidae).

Cuticular hydrocarbons were used to differentiate among the following North American populations of Aedes albopictus: Chicago, Ill.; Milford, Del.; Jacksonville, Fla.; San Antonio, Tex.; New Orleans, La.; Houston, Tex.; and Lexington, Ky. Forty cuticular hydrocarbon peaks were identified from each population using gas chromatography electron impact-mass spectrometry: 16 n-alkanes, 21 monomethylalkanes, and 3 dimethylalkanes. Fourteen peaks occurred at equivalent chain lengths greater than 38.65 and consisted of complex mixtures of dimethyl- and trimethylalkanes. Quantitative analyses were performed on pooled samples of five females from each population using flame ionization gas chromatography. All populations contained the same cuticular hydrocarbons, but showed differences in percent composition. Five of seven populations were separable by discriminant analysis of hydrocarbon components.

Aedes↗

PubMed1990

Habitat and temporal partitioning of tree hole Culicoides (Diptera: Ceratopogonidae).

Spring emergence patterns of tree hole Culicoides were examined at 11 geographic locations. Habitat selection was one mechanism of partitioning used by Culicoides. One group (3 species) occupied tree holes with standing water (wet), while the other (7 species) inhabited tree holes without standing water (dry). The wet tree hole species had sustained emergence patterns, emergence maintained over several consecutive weeks. The dry tree hole species had phasic or biphasic emergence lasting fewer days or occurring as 2 short periods. In both dry and wet habitats, species emerged in a temporal sequence. This temporal sequence was disrupted if a species occupied a type of tree hole (wet/dry) from which it did not normally occur.

Animals↗