Carbon loss from roots of wheat cultivars

The amounts of organic materials released into soil from roots during the first 4 weeks of growth were determined for 11 cultivars of wheat (Triticum aestivum L.). Carbon loss from roots was measured by supplying ¹⁴CO₂ continuously to the shoots and measuring the ¹⁴C content of the roots, root-free soil, water-soluble material and CO₂ flushed from the root chamber. Six cultivars were compared in each of two experiments, with the cultivar Condor common to both experiments. There were no significant differences between cultivars, relative to Condor, for ¹⁴C activity present in soil, roots, water-soluble material or rhizosphere CO₂. There was a significant difference between cultivars in experiment 1, but not in experiment 2, for the variate log₁₀ (¹⁴C lost from roots: ¹⁴C translocated to roots).There was evidence that a reduction in growth temperature, within the range 10–15°C, increased carbon loss from wheat roots into the rhizosphere.     

Extraction,purification and properties of soil hydrolases

Invertase, cellulase, phosphatases, protease and β-glucosidase were extracted from permanent pasture soil with 0.2 M phosphate buffer (pH 8) in the presence of 0.2 M EDTA. This extract was further treated with ammonium and salmine sulphates. Attempts were made to fractionate these enzyme activities by gel and anion-exchange chromatography. Specific activities were estimated in all fractions and some characteristics of the purified enzymes (optimum pH, temperature and substrate concentration, and K_m and V_max) were investigated. The results indicated that extracted enzyme activities occurred partly in soil as a carbohydrate-enzyme complex and partly as a humo-carbohydrate complex.     

Fractionation of organo-mineral complexes by sedimentation and density techniques

Soil samples were fractionated by sedimentation in water and by flotation in heavy liquids to separate complexed and uncomplexed organic and inorganic components. Flocculation of clays in heavy organic liquids was delayed by addition of a surfactant. Heavy liquids and surfactants sorbed by soil components were removed by washing with acetone-water mixtures.In a sample of a red-brown earth, the organic carbon and nitrogen contents were highest in the finest separates. In samples of a ground-water rendzina and a chernozemic soil, the coarse clay and silt separates had the highest organic carbon and nitrogen contents. Organic matter was concentrated in low density fractions in all separates. Carbon/nitrogen ratios were lowest in the finer and heavier separates. Calcium, and to a lesser extent manganese, iron and phosphorus, were concentrated in low density fractions: thus these elements appear to be associated with organic matter and may be important in organo-mineral complex formation. Carbonates, titanium, iron, silicon and potassium were concentrated at the highest densities.Organic fractions < 2.06 g cm^?3 from sand size separates were insoluble in alkali and had wide carbon/nitrogen ratios characteristic of plant debris. The light fractions from fine silt and coarse clay separates were more soluble in alkali but showed high ratios of humic to fulvic materials and high absorption at 280 nm. Such materials were considered to be microbial cell debris and were associated with high contents of disordered aluminium and iron oxides and expanding lattice silicates in 1 to 5 μm aggregates.Heavier fractions, particularly of finer clay separates, contained more fulvic and humic materials of a more aliphatic nature than those in < 2.06 g cm^?3 fractions. It is suggested that physical sorption on clay surfaces may be more important in these fractions. Ellite and kaolinite were concentrated in medium density fractions, and contents of some iron oxides and titanium minerals were highest in fractions > 2.06 g cm^?3. Such minerals plus quartz and feldspars were associated with minor amounts of organic matter or possibly were not involved in organo-mineral associations.     

Comparisons of soil organic matter and its fractions by pyrolysis mass-spectrometry

Pyrolysis mass-spectra from a sample of the A₁-horizon of a soil from southern Spain showed predominant peaks related to furan derivatives similar to those observed from complex polysaccharides in which not only hexoses but also pentoses and deoxyhexoses were constituent units. Smaller peaks, typical for protein materials and phenolic units, were also observed. On the other hand, typical peaks for the methoxyphenols of lignins were very small and indicated only limited amounts of undecomposed lignin residues in this soil sample. Peaks related to benzene or toluene were also very small.Humic acid samples from this soil showed much more prominent signals related to protein materials, benzene and phenolic derivatives and weaker polysaccharide-related signals than did the entire sample. Typical lignin related peaks were small or insignificant. Spectra from the grey or brown humidic acid fractions were much like those of the parent humic acid. Brown humic acid, however, showed stronger signals for nitrogen and sulphur compounds, indicating a higher content of protein-like materials in this fraction. Preparations of humic acid hydrolyzed by 6 N HCl showed in their pyrolysis products a marked increase in phenols and methoxyphenols.In its pyrogram, humin resembled humic acid, but signals for complex polysaccharides were more evident. Lignin-like materials seem not to be higher in this fraction. Hymatomelanic acid showed prominent signals related to polysaccharides and lignin. Pyrograms from the soil polysaccharides showed the characteristic pattern of a complex polysaccharide with the presence of fragments from polymers of amino acids or amino sugars. Fulvic acid spectra showed obvious dissimilarities to those from humic acid in that signals for protein, as well as those related to phenols, were low. Depending upon the isolation method, the fulvic acid preparations showed differing signals related to polysaccharide or phenolic materials.     

Extraction, cleanup, and quantitative determination of aflatoxins B1 ANd M1 in beef liver

A method for the determination of aflatoxin B1 in eggs was applicable for aflatoxin B1 in liver, but ineffective for aflatoxin M1 in liver because of poor recovery of added aflatoxin and interferences in thin layer chromatography. The method was modified by the addition of citric acid to the extracting solvent and ammonium sulfate to the extract solution for removing protein. The elution system for silica gel column cleanup was also changed by substituting methanol for acetone, and adding a step for confirmation of aflatoxin M1 identity. The method has been used successfully for survey and research on aflatoxin residues in animal tissues.     

Distribution of aflatoxins B1 and M1 in contaminated calf and pig livers

The determination of aflatoxins B1 and M1 in multiple sections of livers from 4 calves and 1 pig exposed to high levels of aflatoxins showed a uniform distribution of the aflatoxins in each liver, within the precision of the analytical method used. The thin layer chromatographic method has an expected within-laboratory coefficient of variation of 15%.     

Charcoal column/thin layer chromatographic method for high fructose corn sirup and spectrophotometric method for hydroxymethylfurfural in honey: collaborative studies.

A new spectrophotometric method is described for determining hydroxymethylfurfural in honey in which interfering background absorption of honey is corrected for by use of a bisulfite-treated sample as blank. Two procedures for detecting high-fructose corn sirup (HFCS) in honey were also tested. In one, charcoal column pretreatment is used to concentrate trace oligosaccharides, followed by thin layer chromatography to differentiate those of HFCS from those of honey. The other method depends on measurement of the isomaltose/maltose ratio by gas-liquid chromatography. The charcoal/thin layer chromatographic method for HFCS has been adopted official first action. The bisulfite method for hydroxymethylfurfural has been adopted interim first action.     

Phytotoxins from anaerobically decomposing wheat straw

Phytotoxicity was demonstrated in the aqueous extract of wheat (Triticum aestivum, L.) straw suspensions. When extracts were incubated under anaerobic conditions, the development of phytotoxicity was greater at 20°C than at 10°C. The toxic products formed during incubation depended upon the incubation medium. Acetic and butyric acids were the major toxins produced in liquid straw fermentations during the first 2 weeks. However, after that time the acids did not account for the total toxicity, suggesting formation of unidentified phytotoxins. Acetic, propionic and butyric acids were the toxins formed in sand culture. The development and accumulation of phytotoxins were favored where the sand-straw mixtures were water-saturated. The implications of these findings to wheat cultural practice is discussed.     

Effect of infection of seminal and nodal roots by the take-all fungus on tiller numbers and shoot weight of wheat

A simple technique is described for the separation of seminal and nodal roots of wheat grown in pots. The effect of infection of either of the root-systems of wheat by the take-all fungus on tiller numbers and shoot weight was investigated using a variation of the technique. Both root systems were necrosed by the introduced inoculum of the pathogen to which they were exposed when they were about 7 days old. Although infection of either of the root systems resulted in significant reduction of tiller numbers, only infection of nodal roots caused significant reduction of shoot weight.     

Influence of phosphorus nutrition on sulfur uptake by vesicular-arbuscular mycorrhizae of onion

Mycorrhizal and non-mycorrhizal onions were grown in pots containing soil at two P concentrations. Following ³⁵S injection into the soil, both mycorrhiza) and non-mycorrhizal plants from high P treatments had significantly higher ³⁵S concentrations in roots compared to non-mycorrhizal, low P controls. Mycorrhizal, low P plants had higher concentrations of ³⁵S in shoots than did non-mycorrhizal, low P plants. In a second experiment detached non-mycorrhizal onion roots from plants given a nutrient solution containing P for 26 days before short-term uptake experiments absorbed at greater rates from solution than roots from plants given a complete minus-P nutrient solution. This occurred at all three concentrations of S tested. 1 mM. 10μM, and 0.1 μM. Increased S uptake by mycorrhizal plants can result from increased S absorbing power of roots with enhanced P status.