Harold H. Strain

Bio: Harold H. Strain is an academic researcher from Carnegie Institution for Science. The author has contributed to research in topics: Chlorophyll & Carotene. The author has an hindex of 24, co-authored 45 publications receiving 2121 citations.

[42] Analytical procedures for the isolation, identification, estimation, and investigation of the chlorophylls

Abstract: Publisher Summary This chapter discusses the analytical procedures for the isolation, identification, estimation, and investigation of the chlorophylls. Chlorophylls are the preponderant photosynthetic pigments of the verdant tissues of vascular plants, liverworts, and various algae. The chlorophyll content of plants varies with their age or stage of development, seasons, mineral nutrition, and the intensity and duration of the illumination. The usual or normal chlorophylls have been obtained in various, isotopically labeled modifications by supplying the growing plants with isotopic compounds of carbon and hydrogen. Many fatty or fatlike substances are extracted from plant material with the solvents required for the extraction of the fat-soluble chlorophylls. Therefore, these natural contaminants must be considered in the selection of methods for investigation of the green pigments. The most conspicuous contaminants are the yellow and orange carotenoid pigments. Chlorophylls have many striking physical properties in common. They are green to gray-green and purple pigments with pronounced absorption bands in the blue-green and red spectral regions. They are strongly fluorescent, the wavelength of the emitted light usually corresponding to that of the principal absorption band in the red spectral region.

Mechanisms of Cadmium Mobility and Accumulation in Indian Mustard

Abstract: Indian mustard (Brassica juncea L.), a high biomass crop plant, accumulated substantial amounts of cadmium, with bioaccumulation coefficients (concentration of Cd in dry plant tissue/concentration in solution) of up to 1100 in shoots and 6700 in roots at nonphytotoxic concentrations of Cd (0.1 [mu]g/mL) in solution. This was associated with a rapid accumulation of phytochelatins in the root, where the majority of the Cd was coordinated with sulfur ligands, probably as a Cd-S4 complex, as demonstrated by x-ray absorption spectroscopy. In contrast, Cd moving in the xylem sap was coordinated predominantly with oxygen or nitrogen ligands. Cd concentrations in the xylem sap and the rate of Cd accumulation in the leaves displayed similar saturation kinetics, suggesting that the process of Cd transport from solution through the root and into the xylem is mediated by a saturable transport system(s). However, Cd translocation to the shoot appeared to be driven by transpiration, since ABA dramatically reduced Cd accumulation in leaves. Within leaves, Cd was preferentially accumulated in trichomes on the leaf surface, and this may be a possible detoxification mechanism.

Plant Growth Substances Produced by Azospirillum brasilense and Their Effect on the Growth of Pearl Millet (Pennisetum americanum L.)

Abstract: Azospirillum brasilense, a nitrogen-fixing bacterium found in the rhizosphere of various grass species, was investigated to establish the effect on plant growth of growth substances produced by the bacteria. Thin-layer chromatography, high-pressure liquid chromatography, and bioassay were used to separate and identify plant growth substances produced by the bacteria in liquid culture. Indole acetic acid and indole lactic acid were produced by A. brasilense from tryptophan. Indole acetic acid production increased with increasing tryptophan concentration from 1 to 100 μg/ml. Indole acetic acid concentration also increased with the age of the culture until bacteria reached the stationary phase. Shaking favored the production of indole acetic acid, especially in a medium containing nitrogen. A small but biologically significant amount of gibberellin was detected in the culture medium. Also at least three cytokinin-like substances, equivalent to about 0.001 μg of kinetin per ml, were present. The morphology of pearl millet roots changed when plants in solution culture were inoculated. The number of lateral roots was increased, and all lateral roots were densely covered with root hairs. Experiments with pure plant hormones showed that gibberellin causes increased production of lateral roots. Cytokinin stimulated root hair formation, but reduced lateral root production and elongation of the main root. Combinations of indole acetic acid, gibberellin, and kinetin produced changes in root morphology of pearl millet similar to those produced by inoculation with A. brasilense. Images

Consistent sets of spectrophotometric chlorophyll equations for acetone, methanol and ethanol solvents.

Abstract: A set of equations for determining chlorophyll a (Chl a) and accessory chlorophylls b, c 2 , c 1 + c 2 and the special case of Acaryochloris marina, which uses Chl d as its primary photosynthetic pigment and also has Chl a, have been developed for 90% acetone, methanol and ethanol solvents. These equations for different solvents give chlorophyll assays that are consistent with each other. No algorithms for Chl c compounds (c 2 , c 1 + c 2) in the presence of Chl a have previously been published for methanol or ethanol. The limits of detection (and inherent error, ± 95% confidence limit), for chlorophylls in all organisms tested, was generally less than 0.1 µg/ml. The Chl a and b algorithms for green algae and land plants have very small inherent errors (< 0.01 µg/ml). Chl a and d algorithms for Acaryochloris marina are consistent with each other, giving estimates of Chl d/a ratios which are consistent with previously published estimates using HPLC and a rarely used algorithm originally published for diethyl ether in 1955. The statistical error structure of chlorophyll algorithms is discussed. The relative error of measurements of chlorophylls increases hyperbolically in diluted chlorophyll extracts because the inherent errors of the chlorophyll algorithms are constants independent of the magnitude of absorbance readings. For safety reasons, efficient extraction of chlorophylls and the convenience of being able to use polystyrene cuvettes, the algorithms for ethanol are recommended for routine assays of chlorophylls. The methanol algorithms would be convenient for assays associated with HPLC work.