Lysis of mycelium ofFusarium oxysporum f. sp.udum in soil amended with organic matters

Summary Autoclaved or natural field soil amended with 0.1 to 5.0 per cent (W/W) of margosa cake, rice husk and sawdust with or without supplemental nitrogen were tested for lytic activity and bacterial numbers. Generally, non-amended autoclaved soil caused little or no lysis of mycelium ofF. oxysporum f. sp.udum; non-amended natural soil caused more lysis. Amendment of soil with margosa cake, rice husk or saw-dust with or without supplemental nitrogen greatly enhanced its lytic effect on the fungus. The degree of lysis depended on the dosage of amendment used and the stage of its decomposition in the soil. The extent of lysis increased as the bacterial population increased. Amongst bacteria,Bacillus subtilis was very common in most lytic zones.     

Contribution of bacterial cell nitrogen to soil humic fractions

Summary Living cells ofSerratia marcescens, uniformly labelled with¹⁵N, were added to samples of maple (Acer saccharum) and black spruce (Picea mariana) forest soils. After different periods of incubation from zero time to 100 days, the soils were subjected to alkali-acid and phenol extraction to provide humic acid, fulvic acid, humin and humoprotein fractions. Significant amounts of the cell nitrogen were recovered in the humic and fulvic acids immediately after addition. After incubation, less cell, nitrogen appeared in the humic acid and more in the fulvic acid. The amount of cell nitrogen recovered in the humin fraction increased with incubation. Roughly 5 to 10 per cent of the added cell nitrogen was found as amino acid nitrogen from humoprotein in a phenol extract of the humic acid. The data are consistent with the occurrence of co-precipitation of biologically labile biomass nitrogen compounds with humic polymers during the alkaline extraction procedure involved in the humic-fulvic fractionation.     

Phytochrome mediated induction of nitrate reductase activity in etiolated maize leaves

The effects of red and far-red light on the enhancement of in vitro nitrate reductase activity and on nitrate accumulation in etiolated excised maize leaves were examined. Illumination for 5 min with red light followed by a 4-h dark period caused a marked increase in nitrate reductase activity, whereas a 5-min illumination with far-red light had no effect on the enzyme activity. The effect of red light was completely reversed by a subsequent illumination with the same period of far-red light. Continuous far-red light also enhanced nitrate reductase activity. Both photoreversibility by red and far-red light and the operation of high intensity reaction under continuous far-red light indicated that the induction of nitrate reductase was mediated by phytochrome. Though nitrate accumulation was slightly enhanced by red and continuous far-red light treatments by 17% and 26% respectively, this is unlikely to account for the entire increase of nitrate reductase activity. The far-red light treatments given in water, to leaves preincubated in nitrate, enhanced nitrate reductase activity considerably over the dark control. The presence of a lag phase and inhibition of increase in enzyme activity under continuous far-red light-by tungstate and inhibitors of RNA synthesis and protein synthesis-rules out the possibility of activation of nitrate reductase and suggests de novo synthesis of the enzyme affected by phytochrome.     

The relation between nitrogen percent and dry weight of inoculated legumes

Summary Results of numerous tests of tropical and temperate legume hosts and Rhizobium strains accumulated between 1952 and 1966 were examined for a relation between N percent (y) and dry weight per plant (x). The data fitted the equation y=A–be^–cx. The most effective Rhizobium strains can be selected on the basis of dry matter yields of whole plants or plant tops only, without the need for N analyses, using statistical analyses. A previously proposed method which employs the linear relation between N-yield and dry matter yield was shown to apply only when data for strains which are not fully effective are excluded.It is postulated that symbiotically fixed N forms a different compound from that resulting from applied mineral N and that this compound cannot be remobilised before flowering.deceased     

Nitrogen mineralization in acid sulfate soils

Summary Mineralization of soil nitrogen studies with two acid sulfate soils under anaerobic and aerobic incubation at 30°C for 2 weeks showed that the mineral N was released and accumulated entirely as NH ₄ ⁺ in both soils. Nitrification did not occur in either of the soils under conditions that stimulate nitrification. The acid sulfate soils studied release good amounts of mineralizable N, and, because of lack of nitrifying activity, denitrification may not be a serious problem in these soils.     

Effect of heating on properties of some soils from Southern Nigeria and growth of rice

Summary The effect of heating on the properties of Apomu (Psammentic Usthorthent), Egbeda (Oxic Paleustalf) and Gambari (Typic Plinthustalf) surface soils were studied under laboratory conditions. Heating at low temperatures (100°C) have no detrimental effects on soil properties, on the contrary it increased the soil extractable P, Mg, Fe, Mn and Zn levels. Pronounced reductions in total N, Org. C, Org. P and extractable Ca and Mg levels and marked increases in extractable P, Zn, Mn and Fe were observed by heating to 200°C. Heating to 500° had an adverse effect on soil chemical and physical properties.Plant height and dry matter yeild of rice plants were higher when grown on Egbeda soil previously heated to 100°C. With addition of N, P and K there was no observed beneficial effect of the heating treatment. Rice plants grown on Egbeda soil previously heated to 200°C showed high uptake of Mn. Plants grew badly in soil previously heated to 500°C.     

Effects of accumulation of 3-O-methylglucose on levels of endogenous osmotic solutes in Chlorella emersonii

Abstract. Regulation of the concentration of osmotic solutes was studied in Chlorella emersonii grown at external osmotic pressures (II) ranging between 0.08 and 1.64MPa. NaCl was used as osmoticum. The total solute content of the cells was manipulated by applying 2 mol m⁻³ 3- O -methylglucose (MG), which was not metabolized, and accumulated at concentrations ranging between 60 and 230 mol m⁻³ within 4 h after its addition to the medium. Methylglucose uptake resulted in decreases in concentrations of proline and sucrose, the two solutes mainly responsible for osmotic adaptation of C. emersonii to high external II. The responses were consistent with the hypothesis that proline and sucrose concentrations are controlled by a system of osmotic regulation, with turgor and/or volume as a primary signal. Short-term experiments showed that even very small increases in turgor and/or volume, due to accumulation of methylglucose, resulted in large decreases in proline and sucrose. Over the first 30-60 min the total solute concentration in the cells increased by at most 15 osmol m⁻³ which would represent an increase in turgor pressure of at most 0.04 M Pa. Yet, the decreases in proline and sucrose were as fast as those in cells exposed to a sudden decrease of 0.25 MPa in external II, when the turgor pressure would have increased by at least 0.15 MPa. High concentrations of methylglucose in cells grown at high II did not affect the rapid synthesis of proline and sucrose which started when the cells were transferred to yet higher II. Thus, methylglucose had no direct effects on proline and sucrose metabolism, and it has been assumed that it acted solely as an inert osmotic solute within the cell.     

Benthic macroinvertebrates of northwestern lake victoria,East Africa: Abundance,distribution, intra-phyletic relationships and relationships between taxa and selected element concentrations in the lake-bottom sediments

Phytoplankton assemblage and seston composition of the San José's gulf (Argentine, 42° S) were studied during a period of two years. Cell counts, chlorophyll, particulate nitrogen and particulate carbon determination were made. Phytoplankton synecology was studied using principal component analysis.

     

Distribution and movement of toxaphene in anaerobic saline marsh soils

The biological oxygen demand (BOD) of filtered water from Lake Wingra, Wisconsin is significantly higher in the littoral zone than in the pelagial zone. Laboratory experiments indicate that BOD is not influenced by water temperature at the time of sampling or by enrichment with nitrate or ammonia. Rather, enrichment with macrophyte leachate sharply increases BOD, and enrichment with phosphate produces a small but significant increase in BOD. We conclude that high BOD in littoral waters of the lake is an indication of production of labile organic matter in the water by dense beds of the macrophyte Myriophyllum spicatum.     

Inhibitory effect of ethanol on growth and solute accumulation by Saccharomyces cerevisiae as affected by plasma-membrane lipid composition

Incorporation of ethanol (1.0 or 1.25 M) into exponential-phase cultures of Saccharomyces cerevisiae NCYC 366 growing anaerobically in a medium supplemented with ergosterol and an unsaturated fatty acid caused a retardation in growth rate, which was greater when the medium contained oleic rather than linoleic acid. Ethanol incorporation led to an immediate drop in growth rate, and ethanol-containing cultures grew at the slower rate for at least 10 h. Incorporation of ethanol (0.5 M) into buffered (pH 4.5) cell suspensions containing d-[6-³H] glucose, d-[1-¹⁴C] glucosamine, l-[U-¹⁴C] lysine or arginine, or KH₂ ³²PO₄ lowered the rate of solute accumulation by cells. Rates of accumulation of glucose, lysine and arginine were retarded to a greater extent when cells had been grown in the presence of oleic rather than linoleic acid. This difference was not observed with accumulation of phosphate. Ethanol was extracted from exponential-phase cells by four different methods. Cells grown in the presence of linoleic acid contained a slightly, but consistently, lower concentration of ethanol than cells grown in oleic acid-containing medium. The ethanol concentration in cells was 5–7 times greater than that in the cell-free medium.