Mineralogisch-chemische umwandlungen bei der verwitterung pyroklastischer gesteine auf teneriffa (Kanarische Inseln)

In a weathering profile on pyroclastic material four phases of volcanic activity could be defined by mineralogical analysis. Halloysite in 10 Å- and 7 Å-modifications is the predominant new mineral formed by weathering processes. Various degrees of development of this clay-mineral were found in scanning microscopy.The paragenesis of gibbsite, ilmenite and anatase is characteristic for horizons of most intense weathering. The gibbsite found in distinct layers indicates an alteration of climatic conditions between eruption-stages 3 and 4. Absolute age determinations on potash-felspars from a layer of stage 3 yield 1.53 mio. years (+ 10%).     

Sodium bicarbonate as an extractant for soil phosphate III. Effects of the buffering capacity of a soil for phosphate

An index of the buffering capacity for phosphate of a group of soils was obtained by measuring adsorption of phosphate from dilute solutions of calcium chloride. The effect of buffering capacity on the amount of phosphate initially displaced by solutions of sodium bicarbonate and on the amount of secondary adsorption from bicarbonate was then studied. These two effects were separated using a regression procedure in which the soil: solution ratio was the independent variable.As buffering capacity increased the amount of phosphorus initially displaced decreased and the amount of secondary adsorption increased. Both these changes resulted in a decrease in the amount of phosphate in the extract. The effect of buffering capacity was greater with the Olsen method (soil : solution ratio 1 : 20; 30 min) than with the Colwell method (soil : solution ratio 1 : 100; 16 h). The relation between phosphorus extracted and buffering capacity was of a similar shape to that between effectiveness of fertilizer and buffering capacity. However, the first relation depends on the conditions of extraction and the second on the kind of plant grown and on the conditions of growth. Hence the two relations do not necessarily coincide.The effect of buffering capacity on the proportion of added phosphate initially displaced from the soil became more marked as the period of incubation prior to extraction was increased. Bicarbonate soil tests would therefore indicate that, on soils of low buffering capacity, the decrease with time in availability of applied phosphate would be smaller than on soils of high buffering capacity. This effect differs from that observed with plants.     

Gas-liquid chromatographic analysis of ethephon and fenoprop residues in apples and their decline before and after harvest.

Ethephon (2-chloroethylphosphonic acid) and fenoprop (2-(2,4,5-trichlorophenoxy) propionic acid) may be determined in the same apple sample. After extraction with methanol, 2 separate methylation procedures were required to quantitatively convert each compound. Ethephon was esterified with diazomethane and analyzed by a flame photometric detector in the P-mode. Fenoprop was esterified with boron trifluoride/methanol and analyzed by electron capture gas chromatography. Average recoveries were about 95% at 0.05 ppm for both compounds. The limit of detection was 0.05 ppm for ethephon and 0.01 ppm for fenoprop in a 1 g sample. The persistence of both compounds before and after harvest was studied. Ethephon and fenoprop were applied simultaneously to apple trees at the recommended concentrations of 300 and 20 ppm, respectively. Ethephon residues averaged 1.6, 0.75, and 0.4 ppm at 2 hr, 10 days, and after washing at 13 days, respectively. The corresponding fenoprop residues were 0.70, 0.025, and 0.024 ppm.     

Infection of wheat seminal roots by varieties of Phialophora radicicola and Gaeumannomyces graminis

The growth of isolates of Phialophora radicicola var. radicicola, P. radicicola var. graminicola, Gaeumannomyces graminis var. graminis, G. graminis var. tritici and Leptosphaeria narmari was compared on the coleoptiles and roots of wheat seedlings. Fungal growth was measured as the extent and density of dark runner hyphae. All except P. radicicola var. graminicola grew on coleoptiles and all grew on roots although only G. graminis var. tritici extensively colonized the root stele. Growth rate on roots was positively correlated with that on agar, P. radicicola var. graminicola and L. narmari growing at about half the rate of the other fungi; hyphal density was high for P. radicicola var. graminicola but relatively low for the other fungi. For P. radicicola var. radicicola, P. radicicola var. graminicola and G. graminis var. tritici growing from buried inocula, the extent and density of hyphae up roots towards the seed was similar to that down, but G. graminis var. tritici caused chocolate-brown stelar discoloration up roots only.Root invasion by P. radicicola var. radicicola, P. radicicola var. graminicola and G. graminis var. tritici was described from sections. Each gave a different pattern of hyphae and host response within an inoculum layer, and progressive changes occurred away from the inoculum. Studies of the rate of penetration by each fungus and the rate and pattern of death of cortical cells explained the differences between fungi. G. graminis var. tritici penetrated living cells in advance of other soil micro-organisms, and hence by hyaline hyphae inducing much lignituber formation as a host resistance reaction. P. radicicola var. graminicola penetrated only senescent or dead cells in association with other soil microorganisms, and hence by dark hyphae, inducing little lignituber formation. P. radicicola var. radicicola was intermediate in all these respects. The high hyphal density of P. radicicola var. graminicola was due to the colonization of cortical cells and spaces by dark, clearly visible, rather than hyaline hyphae, which are invisible in unstained roots. Cell death in the outer cortex explained the observed progressive restriction of growth by all fungi to the inner cortex with increasing distance from the inoculum. Spread by G. graminis var. tritici up roots was ectotrophic relative to the stele but down roots hyphae spread rapidly within the stele. Stelar reactions suggested as resistance mechanisms occurred up roots only. Their absence down roots is attributed to infection disrupting stelar transport.     

Decomposition of algal cells and components and their stabilization through complexing with model humic acid-type phenolic polymers

Axenic cultures of Anacystis, Microcoleus, Plectonema and Synechococcus isolated from Greenfield sandy loam and of Anabaena flos-aquae, Nostoc muscorum and Chlorella pyrenoidosa from other sources were cultured under light and constant aeration and with [U-¹⁴C]-glucose in the nutrient medium. Whole cells, cell walls, cytoplasm and extracellular polysaccharides of selected species readily decomposed in the soil and after 22 weeks between 61 and 81% of the added C had evolved as CO₂. Complexing of cell wall and cytoplasmic preparations from A. flos-aquae and N. muscorum with model humic acid-type phenolic polymers reduced decomposition of the cell walls by 40% and of the cytoplasm by 70%. Over 50% of the residual 14C activity in the soil amended with whole algal cells remained in the 0.5% NaOH-extracted soil. With exception of Microcoleus sp. more of the residual ¹⁴C from cell walls, cytoplasm and polysaccharide fractions was present in the humic acid or fulvic acid fractions.     

Multiple forms of acetyl-naphthyl-esterase activity in soil organic matter

Acetyl-naphthyl-esterase activity has been identified and characterized in organic matter extracted from an A₁ horizon of an Alpine podzol. The temperature optimum of the esterase is about 75° C and its activity rises with increasing pH, without reaching a maximum value in the tested range. The Michaelis constant has been determined as Km = 2.950 mM. Pronase does not disrupt esterase activity. Electrofocusing in acrylamide gel shows several peaks of enzyme activity, which correspond with humic isoelectric bands. The location of acetyl-esterase activity in organic matter is discussed.