Plant materials studied using

Aside from the primary research objective, several other criteria should be considered carefully in selecting and designing a bioassay. These include sensitivity, specificity, response time, reproducibility, plant material, cost, labor, equipment, and space requirements. The bioassay should be highly sensitive to the allelochemical(s) in question. Sensitivity and selectivity are dependent on the plant species and plant material being used as the indicator and on the efficacy of the allelochemical studied. In practice, several plant species should be used as indicator species, some of which are highly sensitive to the test compound(s) and some of which appear to be more resistant. Reproducibility is another key factor. 

Extraction of the plant materials was performed in a flow apparatus similar to that described in chapter 4. The current National Cancer Institute protocol for extracting new plant materials consists of Soxhlet extraction with 95% ethanol. (For comparison purposes a Soxhlet extraction was also done for this study.) Carbon dioxide conditions of 275 bar and 35°C were chosen to achieve a high density at a temperature reasonably close to ambient temperature. About 20 g of plant material were used for each extraction. The material was contacted with 200 standard liters of carbon dioxide in a flow extractor, and the extract that was collected when the carbon dioxide was expanded to ambient pressure was tested in a bioassay test. 

Proper internal standards have to be applied for quantitative analyses performed using any kind of instrumental system. Isotopomers of the analyzed compounds substituted with stable isotopes ( H, and/or are especially convenient internal standards as they have chromatographic properties identical with the native compounds, and the ratio of signal intensity of both types of ions may be easily calculated. Finally, analyses should be performed in a fairly high number of repetitions (above six) due to the biological diversity of plant material studied. 

Essential is also used as the adjective form of the noun essence The mixtures of substances that make up the fragrant material of plants are called essential oils because they contain the essence that is the odor of the plant The study of the composition of essential oils ranks as one of the oldest areas of organic chemical research Very often the principal volatile component of an essential oil belongs to a class of chemical sub stances called the terpenes... 

Hydrolysis using aqueous alkaH has been found to remove ash material including pyrite. A small pilot plant for studying this process was built at the BatteUe Memorial Institute in Columbus, Ohio (74) and subsequentiy discontinued. Other studies have produced a variety of gases and organic compounds such as phenols, nitrogen bases, Hquid hydrocarbons, and fatty acids totaling as much as 13 wt % of the coal. The products indicate that oxidation and other reactions as weU as hydrolysis take place. 

Extraction Procedure. Wheat ( McNair 1813 ) plant material used in this study was harvested from the field in early spring after the wheat had tillered but before heading. The plant material was dried at 50°C for 48 hr. 

N-Monoalkyltryptamines are another group of agents that have not received much attention. N-Methyltryptamine (27) and its 5-methoxy derivative 36 have been detected as constituents of plant materials used by certain South American Indians as hallucinogenic snuffs (109). Because these plant materials are also known to possess the established hallucinogens N,N-dimethyltryptamine (DMT 37) and 5-OMeDMT and since neither N-methyltryptamine (27) nor 5-methoxy-N-methyltryptamine (36) has been studied in the pure form, the effect of these latter two agents in man is presently unknown. 

Microanalytical techniques were first pioneered in the 1960s, and the earliest paper using X-ray microanalysis on plant materials is that of Lauchli and Schwander in 1966 (1). It was soon realized that microanalysis could provide a link between anatomical studies and plant physiology. It allowed scientists who were interested in aspects of plant mineral relations to pursue their interests at a cellular or even subcellular level. Microanalysis, in its various forms, is now a well-established technique, and one that is continuing to develop. 

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