Crop isolation

If the filtrate is of value, it should be transferred to another vessel immediately the crystals have been drained. Frequently, the mother liquor may be con centra ted (suitable precautions being, of course, taken if it is inflammable), and a further crop of crystals obtained. Occasionally, yet another crop may be produced. The crops thus isolated are generally less pure than the first crystals which separate, and should be recrystaUised from fresh solvent the purity is checked by a melting point determination. 

Sodium anthraquinone-p-sulphonate ( silver salt ). Place 60 g. of fuming sulphuric acid (40-50 per cent. SO3) in a 250 or 500 ml. round-bottomed flask and add 50 g. of dry, finely-powdered anthra-quinone (Section IV,145). Fit an air condenser to the flask and heat the mixture slowly in an oil bath, with occasional shaking, so that at the end of 1 hour the temperature has reached 160°. Allow to cool and pour the warm mixture carefully into a 2 litre beaker containing 500 g. of crushed ice. Boil for about 15 minutes and filter off the unchanged anthraquinone at the pump. Neutralise the hot filtrate with sodium hydroxide and allow to cool, when the greater part of the sodium anthra-quinone-p-sulphonate separates as silvery glistening plates ( silver salt ). Filter these with suction and dry upon filter paper or upon a porous plate. A second crop of crystals may be isolated by concentration of the trate to half the original volume. The yield is 40-45 g. 

It has been estimated that of the total U.S. increase in farm output between 1940 and 1955, 43 percent is attributable to increased crop yields per hectare, 27 percent to increases in value added by livestock production, 23 percent to reduction in farm-produced power, and 7 percent to changes in the amount of capital used. While it is not possible to isolate the effect of a single input, it is estimated that increased use of fertilizer accounted for more... 

Potential resources of xylans are by-products produced in forestry and the pulp and paper industries (forest chips, wood meal and shavings), where GX and AGX comprise 25-35% of the biomass as well as annual crops (straw, stalks, husk, hulls, bran, etc.), which consist of 25-50% AX, AGX, GAX, and CHX [4]. New results were reported for xylans isolated from flax fiber [16,68], abaca fiber [69], wheat straw [70,71], sugar beet pulp [21,72], sugarcane bagasse [73], rice straw [74], wheat bran [35,75], and jute bast fiber [18]. Recently, about 39% hemicelluloses were extracted from vetiver grasses [76]. 

The number of reports about hemicelluloses that have been covered by this review indicates the significantly increased importance of all types of hemicelluloses as plant constituents and isolated polymers during the last decade. Attention has been paid not only to known hemicelluloses but also to the primary structure, physicochemical, physical, and various functional properties of hemicelluloses isolated from hitherto uninvestigated plants. The efforts to exploit a variety of plant as potential sources of hemicelluloses were pointed out particularly for agricultural crops, wood wastes, as well as for by-products of pulp and rayon fiber technologies. Many studies were devoted to characterize seed-storage hemicelluloses from plants that have been traditionally applied in food and medicine of many underdeveloped countries to find substitutes for imported commercial food giuns. 

CAM is unlikely to be useful for any of the conventional food crops. Nevertheless, further study of those plants in which CAM is inducible could prove useful since isolation of, for example, the PEP carboxylase gene will permit the isolation of its controlling sequences. This will provide us with another set of stress-specific (drought) promoters and enhancers. Furthermore the PEP carboxylase gene has proved amenable to cloning via the cDNA route (Harpster Taylor, 1986). 

Two isolates of FORL (rj and r ) were provided by Dr. Tello (INIA, Madrid) from diseased tomato crops grown on the Spanish Mediterranean coast (11). Both isolates were maintained as stock cultures on potato-dextrose agar... 

The pathogenicity of DRB to crop plants has been shown to be host-specific (35) and thus is conceivably linked to root exudation. Alstrom (169) found that the pathogenicity of two isolates of Pseudomonas was determined by the major components of the broth culture in which they were applied to bean seedlings. Both isolates were pathogenic to bean seedlings when the broth contained sucrose and peptone or sucrose and yea.st extract. When the broth contained sucrose alone, one isolate was pathogenic and the other was not. Neither isolate was pathogenic when the broth contained yea.st extract or peptone alone (169). 

Specifically for triazines in water, multi-residue methods incorporating SPE and LC/MS/MS will soon be available that are capable of measuring numerous parent compounds and all their relevant degradates (including the hydroxytriazines) in one analysis. Continued increases in liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API-MS/MS) sensitivity will lead to methods requiring no aqueous sample preparation at all, and portions of water samples will be injected directly into the LC column. The use of SPE and GC or LC coupled with MS and MS/MS systems will also be applied routinely to the analysis of more complex sample matrices such as soil and crop and animal tissues. However, the analyte(s) must first be removed from the sample matrix, and additional research is needed to develop more efficient extraction procedures. Increased selectivity during extraction also simplifies the sample purification requirements prior to injection. Certainly, miniaturization of all aspects of the analysis (sample extraction, purification, and instrumentation) will continue, and some of this may involve SEE, subcritical and microwave extraction, sonication, others or even combinations of these techniques for the initial isolation of the analyte(s) from the bulk of the sample matrix. 

The quantity, quality and purity of the template DNA are important factors in successful PGR amplification. The PGR is an extremely sensitive method capable of detecting trace amounts of DNA in a crop or food sample, so PGR amplification is possible even if a very small quantity of DNA is isolated from the sample. DNA quality can be compromised in highly processed foods such as pastries, breakfast cereals, ready-to-eat meals or food additives owing to the DNA-degrading action of some manufacturing processes. DNA purity is a concern when substances that inhibit the PGR are present in the sample. For example, cocoa-containing foodstuffs contain high levels of plant secondary metabolites, which can lead to irreversible inhibition of the PGR. It is important that these substances are removed prior to PGR amplification. Extraction and purification protocols must be optimized for each type of sample. 

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