Proprietes des diphenol oxydases extraites des sols

Properties of diphenol oxidases extracted from salts. Salmine and SP-Sephadex C-25 were used to separate the enzyme system associated with humic materials in the neutral extracts of fresh soils (NAFS Extract). Electrophoresis on polyacrylamide gel shows that this preparation is heterogeneous. The elementary analysis of the soil enzyme is C 43·13%; N 5·09%; H 7·21%; O 44·58%. Chromatographic analyses indicate that the soil enzyme contains 53 per cent amino acids, 36 per cent sugars and amino sugars and 10 per cent ammonium and inorganic materials. The soil enzyme has a maximum absorption at 270–280 nm. The soil enzyme degrades the following substrates at the relative rate mentioned in parentheses : d-catechin (298);p-cresol (251); catechol (156); dl-DOPA (100);p-phenylene diamine (59);p-quinol (20) in terms of rate of oxygen absorption. This enzymatic preparation has the properties of an o- and p-diphenol oxidase. The rate of decarboxylation was measured using a radiorespirometer. The following relative values are dl-DOPA-l-¹⁴C (100); dl-tyrosine-l-¹⁴C (35) ; dl-tyrptophan-1-¹⁴C (7); dl-phenylalanine-l-¹⁴C (2). The dl-DOPA-2-¹⁴C was partially degraded to ¹⁴CO₂. The O₂ absorbed and CO₂ (carboxyl) evolved in case of dl-DOPA was in the ratio of 1·8 at 37°C. The activation energy on dl-DOPA was 3·1 and 7·9 kcal/mole/°C for oxygen absorption and decarboxylation respectively. The enzymatic activity on dl-DOPA-l-¹⁴C was optimum in air and inhibited in a N₂ atmosphere. Decarboxylation on dl-DOPA-l-¹⁴C followed the Michaelis-Menten law, from which we found that K_m = 8·3 × 10^?4M for decarboxylation. The oxidative decarboxylation was inhibited by H₂O₂ (74%); KCN (75%); ascorbate (92%); BAL (97%);DIECA(90%).Melanogenesis of dl-DOPA followed first order kinetics. The maximum absorption at 305 nm during melanogenesis shows the formation of dopachrome.     

Etude des diphenol oxydases extraites d'une litiere de foret

Study of diphenol oxidases extracted from beech litter. Lyophilized neutral sterile extract from the fermentation (F) layer of beech litter (NALF Extract) exhibited the chemical characteristics of humic acids. It possessed diphenol oxidase activities. The specific activities (sp. act.), given in parentheses, are expressed in nmoles O₂ absorbed mg C^?1 min^?1: p-crcsol (19.5); catechol (0.6); dl-3(3,4-dihydroxyphenyl)alanine (5.7); d(+) catechine (4.8) and p-phenylenediamine (7.1). The NALF Extract was polydispersed by G100 Sephadex column chromatography. The firsi peak kd ~ 0.05 (fraction I), the intermediate band (fractions II + III) and the second peak k_d ~ 1.02 and 1.38 (fractions IV + V). Diphenol oxidases were localized in fractions I, II and III. Electrophoretic studies have shown that the fractions I, II and III are heterogeneous. Chromatography on DEAE cellulose of fraction I permitted the separation of 30 per cent of the laccase activity in a form which is free from humic material.     

Fixation de la ribonuclease A sur des elements du sol

The immobilization of ribonuclease A on soils constituents (montmorillonite, humic acid, montmorillonite-humic acid complex) is the same with or without sodium cyanoborohydride. The enzyme is not liberated by washing with dilute sodium chloride and this observation is in favor of a great adsorption energy. It is suggested that the different supports inhibited completely ribonuclease activity by combining with the enzyme.     

Decomposition de corps microbiens dans des sols fumiges au chloroforme: Effets du type de sol et de microorganisme

Five microbial species (Aspergillus flavus, Trichoderma viride, Streptomyces sp., Arthrobacter sp., Achromobacter liquefaciens) were cultivated in liquid media containing ¹⁴C-labelled glucose. The decomposition of these microorganisms was recorded in four different soils after chloroform fumigation by a technique related to that proposed by Jenkinson and Powlson, to determine the mineralization rate of microbial organic matter (K_c coefficient). Three treatments were used: untreated soil, fumigated soil alone and fumigated soil supplied with ¹⁴C-labelled cells. Total evolved CO₂ and ¹⁴CO₂ were measured after 7 and 14 days at 28°C.The labelled microorganisms enabled the calculation of mineralization rate K_c (K_c = mineralized microbial carbon/supplied microbial carbon). The extent of mineralization of labelled microbial carbon depended on the type of soil and on the microbial species. Statistical analysis of results at 7 days showed that 58% of the variance is taken in account by the soil effect and 32% by the microorganism effect. Between 35 and 49% of the supplied microbial C was mineralized in 7 days according to the soil type and the species of microorganism. Our results confirmed that the average value for K_c = 0.41 is acceptable, but K_c variability according to soil type must be considered.The priming effect on organic C and native microbial biomass mineralization, due to microbial carbon addition was obtained by comparison between the amount of non-labelled CO₂-C produced by fumigated soils with or without added labelled microorganisms: this priming effect was generally negligible.These results indicate that the major portion of the error of microbial biomass measurement comes from the K_c estimation.     

Les hydrolases du sol et leur association avec les hydrates de carbone

Soil hydrolases and their association with carbohydrates. Active enzymes isolated from soil in the form of carbohydrate-enzyme-complexes could not be separated from each other by DEAE cellulose chromatography. All enzymes measured in this complex were recovered in Chromatographie fractions with different specific activities and variations in carbohydrate contents. There is however, no linear relationship between the quantity of carbohydrates and specific activities of the fractions. The carbohydrate-enzyme-complexes are not glycoproteins, but the enzymes are physically adsorbed on polysaccharides in a non-covalent manner. The essential role of this carbohydrate is to protect the enzyme systems against denaturation or proteolysis, thus ensuring their stability in soil.     

Relations entre la fertilisation et la concentration des nitrates et du potassium dans les feuilles et le rendement et la qualite du mais de table

Abstract

Twenty sweet corn tissue samplings were made from ten field trials during 1974–76. Fertilization had little effect on yields, but a good relationship was found between yields and leaf tissue nitrate and potassium concentrations, in the leaves 40–50 percent developed at the F‐9, F‐13 and F‐14 vegetative stages. The lower and upper tissue nitrate and potassium concentration limits (deficiency and excess) were found to range between 2000 and 3000 ppm nitrate, and 1.5 and 4.2 percent, or 2.0 and 3.25 percent potassium, according to their vegetative development. Excessive nitrogen and phosphorus application decreased kernel tenderness and total solids (sugar) content, but potassium fertilization enhanced total sugar accumulation.     

Distribution et localisation du Zn et du Pb dans un sol complexe situe a l'aplomb d'un gossan en milieu carbonate (Famenne belge)

Within the study area, a sulphide mineralization consisting of marcasite, sphalerite and accessory galena, as well as its subsurface oxidation product, a gossan in which the dominant mineral is goethite, are intricately intermixed with a gangue of calcite. The open profile at the mineralized site shows the succession of two soils: a leached brown soil (Hapludalf) developed in the loessic cover is underlain by a paleosol of the terra fusca type. The presence within the terra fusca of limonitic gravels indicates its genetic relationship with the underlying gossan. This is further confirmed by the distribution of Fe, Pb, Zn and Mn within the different horizons of the profile. The high values of Pb, and Zn, which are found both in the limonitic gravels and in the major B horizon of the terra fusca contrast strongly with the low values for the soil developed in loess.The different particle-size fractions from the major B horizons of both the leached brown soil and the terra fusca have been submitted to a selective dissolution method using five reagents sequentially (ammonium acetate, hydroxylamine, ammonium oxalate in darkness, ammonium oxalate under ultra violet (U.V.) radiation, strong acids). The crystalline iron oxides (which are dissolved by ammonium oxalate under U.V.) are concentrated in the sand fractions of the terra fusca and their extraction is accompanied by that of Zn. In the same particle-size fraction, hydroxylamine dissolves selectively Mn oxides and also extracts the major part of the Pb. A similar behaviour is observed when the same extraction sequence is applied to a limonitic gravel. The best evidence for the underlying mineralization is therefore found in the coarse and very coarse fractions of the terra fusca where the disintegration products of the gossan are concentrated. These products are absent in the loess covering the terra fusca.     

Influence de gels mineraux et d'argiles sur la cristallogenese du carbonate de calcium a partir des solutions bicarbonatees

The precipitation of calcium carbonate is obtained from a bicarbonate solution added with silica gels, silico-mangnesian gels, ferric gels and clay minerals.Two methods have been performed. The first one consists of a quick removal of CO₂; the second one refers to settled solutions. Identification of various carbonates is obtained by infra-red spectroscopy. Morphology of crystalline shapes are analysed with scanning electron microscope.It is etablished:

(i) silica gels are not good inhibitors of calcite;

(ii) silico-magnesian gels reduce the time of precipitation and promote the deposition of “disordered” calcite (intermediate hydrated form between amorphous calcium carbonate and calcite) and (OH) aragonite;

(iii) ferric gels inhibit very strongly calcite; then, vaterite and aragonite are deposited;

(iv) at the least, the presence of clay minerals promote the stabilization of amorphous calcium carbonate and “disordered” calcite.

The gels and the minerals which are here tested and recognized in soils take therefore an active part in the kinetics of precipitation and in the nature of the calcium carbonates.     

Sterilisation thermique des sols et degradation des herbicides

A residual microbial population was found in sterilized soils following three autoclavings (20 min—120°C). This microorganism appeared after certain soil treatments: addition of chemical products or physical treatment. It was identified as Pseudomonas maltophilia. Degradation of two herbicides earbamates, chlorbufam and barban, was observed with a culture of P. maltophilia. This degradation was not observed in soil.     

Laccases de Polyporus versicolor dans le sol et la litiere

Laecases of Polyporus versicolor in soil and litter. The laccases forms A and B, prepared from Polyporus versicolor, were compared with the laccases liberated from soil and litter by means ofchromatography on G100 Sephadex and DEAE DE 52 Cellulose. It appears that the soil and litter enzymes were of the form A that is strongly electronegative. These results suggest that because of their negative charges, laccases A, were weakly adsorbed onto humic colloids. Consequently, protection might be given to the active sites of the enzymes without preventing the formation of “humo-laccases” complexes in soil and litter.     

Effets de quelques pesticides sur la colonisation d'un substrat par le Trichoderma harzianum rifai en presence des autres champignons du sol

The effects of some pesticides upon substrate colonization by Trichoderma harzianum Rifai in the presence of other soil fungi.A herbicide (propyzamide) and 5 fungicides (benomyl, quintozene, vinclozolin. thiram, prothiocarb) were added at various concentrations to two Trichoderma harziunum-enriched garden soils. After thorough mixing, followed by solidifying with water agar, discs of these mixtures were cut with a cork-borer and transferred to a non specific nutrient medium (PDA). The development of T. harzianum on the agar, around each implant, was estimated after incubation for 1 week at 28°C.In the presence of other soil fungi, T. harzianum development was scarcely or not at all modified by prothiocarb, propyzamide and quintozene. It was highly depressed by benomyl. Vinclozolin was only slightly inhibitory. In our experimental conditions, T. harzianum development was strongly enhanced by thiram, even at a high dosage (300 μg ml^?1).The limits and the advantages of the method are estimated and the results are discussed in view of practical applications.     

Caracteristiques des humoacides et des humines de deux rankers Pyreneens

The authors studied humic acids and remaining and extractable humines of a Moder on paleo and neo-rankers at two stations in the Pyrenean mountains at altitudes of 2600 and 2100 meters. Very distinct in their morphological and physio-chemical characters, they can be considered as a stational pedoclimax.The neo-rankers have an acid and fulvic moder and are more rich in iron, aluminium and silica, than the paleo-rankers having a humic and less acid moder.The humic fraction does not contain any lignin core and contains more aluminium, iron and magnesium than humines even though the latter has a higher ash ratio. Quantitatively they differ in their contents of minerals, carbon, different nitrogens and sugar compounds and qualitatively in their contents of amino-acids and in their age determined by C¹⁴.     

Influence du niveau d'alimentation hydrique sur les variations du diametre des tiges,du potentiel hydrique,de la resistance stomatique,de la transpiration et de la photosynthese de l'aubergine (Solanum melangena L.)

The aim of this preliminary work was to test some biological criteria used for irrigation control. Microvariations of stem diameter, photosynthesis and plant growth were compared with previously recommended parameters such as leaf water potential and stomatal resistance, transpiration ...?Measurements were made on eggplants, grown in pots under a plastic greenhouse. Some of the pots were watered daily to compensate for transpiration losses. From Day J, watering was stopped for the “dry treatment” pots.As early as Day J + 2 stomatal resistances of both sides of the leaves were a little higher for the dry treatment than for the watered one. Net photosynthesis was only slightly reduced at the end of the afternoon.From Day J + 3, differences between the treatments increased for all the criteria: basic water potential, stomatal resistance, net photosynthesis. The stem diameter of the unwatered plants decreased and became smaller than for Day J + 2. All these results are coherent and indicate the interest of the stem diameter variation measurement as an irrigation control criterion. Compared with other criteria, it has the advantage of not needing any measurement on control plants, as water is the only acting factor.Moreover, for the watered plants, it has been pointed out that the stem diameter increase was linearly related to the cumulated net photosynthesis of the previous days. Such a relation would be an interesting criterion for greenhouse climate control.     

Essai de correlation entre proprietes biochimiques d'un sol salsodique et sa biomasse

In order to study the influence of salinity on the biological activity of soils, experiments were performed in a saline alkaline soil from Tunisia (mediterranean semi-arid climate) and compared with results of similar experiments performed in a pelosol from a semi-continental climate (Lorraine, France). Both soils had received ¹⁴C-labelled maize straw.The microbial biomass was estimated by a modified Jenkinson's method and also by measurements of ATP content. The microbial activity was determined by measurements of total and ¹⁴CO₂ evolved.The results have shown an inverse correlation between the salinity determined by electrical conductivity and the biomass estimations and its activity. The higher ATP con tent (141.5 ng · 100 g^?1 soil) was observed in the pelosol and the lower (99.4 ng · 100 g^?1) in the saline soil. Simultaneously and respectively in the pelosol and the saline soil the biological carbon evolved was 114 and 54 mgC 100 g^?1 soil and the average rate of ¹⁴C mineralization was 0.82 and 0.45 mgC · 100 g^?1 soil.Results have also shown that CO₂ evolved after sterilization and reinoculation is not only provided by mineralization of microbial biomass during fumigation but also from interaction between organic-matter and CHCl₃; this interaction is more intense in the saline soil.     

Decarboxylation des acides amines aromatiques-1-14C par les extraits de sol

Decarboxylation of the aromatic amino acids-1-¹⁴C by soilextracts: Neutral aseptic extracts of fresh soils (NAFS Extract) from forest, meadow and cultivated soils decarboxylate dl-DOPA-l-¹⁴C; dl-tyrosine-l-¹⁴C; dl-tryptophane-l-¹⁴C and dl-phenylalanine-l-¹⁴C with relative decarboxylation rates of 100; 30; 10; 0 respectively. The decarboxylation rate of dl-DOPA-l-¹⁴C has a highly significant correlation with the concentration of mineral fraction in the NAFS Extract. This result suggests that, in soil, the enzymatic system is protected by the easily extracted soil minerals. Considering the high value of E_act. (23 kcal/mole/degree), the catalytic power of the enzymatic system associated with the NAFS Extract is low. The decarboxylation rate of dl-DOPA-l-¹⁴C is optimum under aerobic conditions at pH 7 and at 37°C.The kinetic of the reaction follows the Michaelis-Menten law with K_m = 2·1 × 10^?3 M. The nature of the enzymatic system associated with the NAFS Extract is discussed.