PREPARATION OF AQUEOUS EXTRACTS OF SOLUBLE NITROGEN FROM PLANT TISSUES
| Autor: | J. W. Shive, H. E. Clark, O. W. Davidson |
|---|---|
| Rok vydání: | 1934 |
| Předmět: | |
| Zdroj: | Plant Physiology. 9:817-822 |
| ISSN: | 1532-2548 0032-0889 |
| DOI: | 10.1104/pp.9.4.817 |
| Popis: | It has been shown by Chibnall (3), and by Tottingham et al. (9), that the drying of plant tissues before extraction changes the proportional distribution of nitrogen among the nitrogenous constituents. Accordingly, only aqueous extracts from fresh plant tissues have been used by Chibnall (2), Vickery and Pucher (10), Nightingale (7), and Murneek (6) in studies on the nitrogen metabolism of plants. Their results have shown that the various nitrogenous fractions included in the aqueous extracts are indicative of the course of nitrogen metabolism in plants. The relative advantages of the solvents commonly employed in the preparation of plant extracts have been discussed by other investigators (4, 5). Hot alcohol used in concentrations of 50 to 80 per cent, has been recommended because it stops enzymatic action quickly, precipitates some or all of the proteins, and is a good solvent for the relatively simple nitrogenous compounds. Appleman and Miller (1) found that extracts of potato tubers prepared by the use of hot alcohol yielded practically the same amounts of non-protein nitrogen as did cold-water extracts. Hot water will destroy enzymes about as rapidly as will hot alcohol, however, and it is a slightly better solvent for the simple nitrogenous constituents than is the latter. By the use of hot water, cell membranes are killed quickly and thereby rendered permeable to the soluble constituents. Furthermore, the use of hot water simplifies the subsequent analytical procedure, since certain nitrogen determinations can be made only with alcoholfree samples (4). In the preparation of aqueous extracts of soluble nitrogen, Tottingham et al. (9) and Nightingale (7) ground the plant tissues in a mortar with the aid of sand. The preparation of extracts by this method is attended with much labor and requires considerable time. This in turn limits the number of samples that can be extracted within a given period. Moreover, the time required for the preparation of an extract in this manner permits a loss of nitrogen or a change in the distribution of the nitrogenous fractions in plants containing such unstable compounds as some of the cyanogenetic glucosides (8). |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|